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Icom IC-746 FAQ

1. Page 33 of 113 2003 02 08 IC 746 FAQ Connecting and operating an LDG tuner is exactly the same they even make a cable specifically for the task Connecting and operating an SGC tuner is almost the same you ll have to make your own interface cable Instructions for that are at http www sgeworld com products Couplers icom706 html Sure the page says its for the IC 706 but the external ATU interface is identical to that of the IC 746 Once wired up operation will be just like for the AH 4 Finally you could just fake the IC 746 into thinking that there is an ATU out there with a dummy plug like that available from W2ENY at http members fortunecity com w2eny tenatuner Operation is similar to that for the other tuners but transmission stops after an 8 second timeout instead of by tuner acknowledgement You can even build this yourself based on the information at http www mods dk mods php3 radio icom amp model ic 706 amp selectid 1864 or http www gqsl net wb8rcr 706Tune html http www qsl net g 4fzn 706cct gif Don t mind that the info says its for the IC 706 all Icom rigs from this era use the same circuitry connector 3 2 15 Why doesn t the rig SWR meter match my external SWR meter Its normal for different points along the RF feed to register different SWR readings The SWR meter in the 746 reads the SWR between the final amplifier stage and the tuner Your external SWR meter reads the SW
2. 2 14 Where can I find info on other Icom rigs 2 15 Where is info on the 706 718 756 765 735 This FAQ is devoted to the IC 746 As of November 2001 we do not know of any FAQ s devoted to other Icom models However as of Jan 2002 a project was underway to start accumulating and centralizing Icom information at http www qsl net icom While the coordinators of this list already have their hands full they would be glad to advise help and collaborate with people interested in maintaining other FAQs Much of the generic information in this FAQ is applicable to other Icom rigs but please use common sense when trying to apply it For general information on other Icom rigs try Icom s WWW site at http www icomamerica com Icom e mail discussion group at http www qth net Usenet newsgroup news rec radio amateur equipment The Icom Amateur Radio Information Pages at http www qsl net icom Page 18 of 113 2003 02 08 IC 746 FAQ The definitive collection of mods for all makes and models of amateur radio equipment is at http www mods dk Yahoo Groups hosts more than 40 e mail WWW discussion groups related or devoted to Icom equipment Here are some of the more than 50 Icom related groups there http groups yahoo com group icomr2 http groups yahoo com group ICOMR3 http groups yahoo com group ic706 http groups yahoo com group ICOM706 http groups yahoo com g
3. 7 5V 6 1 V 5 1 V OV 4 1V 3 2 V 5 ALC Connected directly to pin 5 on ACC 1 6 VSEND Input Output for VHF When grounded transmits Goes to ground when transmitting Ground level 0 5 to 0 8 V dc Output current lt 20 ma Input current lt 200 ma 7 13 8 V Connected directly to pin 7 on ACC 1 8 6 by the front panel mic gain control 8 7 Obvious Solution The connector you need is often called an OEM T connector You can order Icom part number OPC 025A or OPC 025D from any of the major ham equipment retailers for a pre wired cable Icom s cable compatibility chart lists the OPC 025A Most retailers sell the OPC 025D Both apparently work The OPC 025A is rated for 20 amps while the OPC 025D is rated for Does audio to pin 4 of ACC 1 trigger the VOX No Pin 4 of ACC 1 does not trigger the VOX circuitry nor is the level of that input affected Where can get replacement power connectors 30 amps Most hams prefer the beefier cables Page 92 of 113 2003 02 08 IC 746 FAQ BUX CommCo sells equivalent cables connectors that are cheaper You can find more info at http www buxcommco com Better Solution Rather than finding another Icom connector many folks put inexpensive connectors on the cables of all their rigs and power sources That way they can use any rig with any supply no matter what brand This style of setup is particularly handy for switching
4. Added Q A on non standard repeater offsets Updated info on internal external ATU usage Corrected amplifier question numbers Added Q A about 100 duty cycle Added a few more WWW links Added another magazine article More info on gt 100w power output Added Q A about setting NR level General cleanup links TOC etc More info on SEND relay isolation circuits Added SM reference for BCB ATT mod Added another magazine article Expanded info about gt 100w output alignment Started moving mods into a seperate section More updated info on LCD Q302 failures Added Q A on long wire antennas More info on amp ant switching Added Q A about internal external SWR meters Updated Q As on split TX RX antennas Added more info on switching amps with ACC 1 2 Added Service Manual Discrepancies Added microphone mod Yet more info on SEND relays Even more info on Q302 and LCD problems Added more info on voltage boosters Minor editing formatting of mods More info on LCD driver repair More info on SEND relay limitations Added more info on Q302 and LCD burnout Added alternative prevention to LCD blow out Added mod to MONITOR level Updated Q A on external tuner activation Added Q A about internal ATU gotchas Updated Q As on non Icom amp hook up Updated info on installing Inrad filters Added more TLAs to glossary Added Q A about external ATUs Added citation for latest QST article Minor addition to NB question Updated some of
5. Hi Fi SSB audio is a hot topic within ham radio Everyone wants the best transmitted audio they can get however not everyone agrees upon what best is The issues become even more heated once you add concerns over excessive bandwidth usage and splatter The characteristics capabilities of the IC 746 allow this FAQ to take a neutral position in the debate Stock the IC 746 has a SSB bandwidth of about 2 4 Khz That bandwidth can be widened to as much as 3 4 Khz without deleterious effects the FAQ describes how elsewhere Pushing beyond that point requires more effort than most people are willing to invest A lot of Hi Fi activity occurs on or about 14 178 Mhz There is also an active group of hams at http groups yahoo com group hfssbaudio 8 11 How does one improve the fidelity of a received signal Here is a checklist of several possible actions not in any particular order Assure precise tuning Use a high quality external speaker or headphones Try to run without pre amps or with attenuator Reduce the RF gain increase AF gain to compensate Set TPBT to widest bandwidth Use wider IF filters Lower level of NR counterclockwise to the left Turn off NR Turn off ANF Turn off NB Set AGC to SLOW Be sure input power is greater than or equal to 13 5 Vdc Use an external AF amp via the ACC ports Equalize the AF output Page 94 of 113 2003 02 08 IC 746 FAQ 8 12 How does one improve transmission fidelity H
6. But FM digital and CW will generally pull 18 20 amps at full power Consider the following measurements on 20m into a dummy load IC 746 Transmit Current vs Input Voltage Amps Volts e Current at maximum RF output CVV Data measured by KB9SSS July 2001 Amps 0 1a Volts 0 02 Continuous vs Intermittent Load There are issues concerning a supply s intermittent peak or surge capacity A supply might be rated for 16 amps continuous and 20 amps peak Normally the IC 746 runs at about 2 3 amps for receive and only hits the 20 amp maximum during transmission Thinking of transmitting as peak or intermittent activity can lead one to think that such a supply is acceptable It might even be However a problem develops when we try to define what peak or intermittent activity is Page 25 of 113 2003 02 08 IC 746 FAQ Everyone would agree that transmitting for 3 minutes at 20 amps till the repeater time out cuts you off is not a peak How short a time constitutes a peak and at what duty cycle Without some sort of specification or standard peak and intermittent could mean just about anything Most of us feel more comfortable with a better safe than sorry approach This dual rating system for power supplies is a great source of confusion Specifically you could buy a power supply rated for 20A and have it fail under full load The Astron RS 20 and Pyramid PS 21 are examples of such supplies
7. the solder might melt That slowly deteriorates the soldering material resulting in a lost connection and a cooked transistor He has a feeling that future cooked transistors can be prevented by simply unsoldering the transistor cooling fin to lift it and lengthening the center leg to establish connection at the cooling fins soldering point AH6LE counters that if the transistor gets hot enough to melt solder 300 degrees or so then there are other more serious problems Most solid state devices won t survive such temperatures thus we re seeing the result not the cause The repair One of the techs at MTS a company that repairs Icom gear told K8UT that the repair is not difficult but he does not recommend it to those without soldering desoldering experience The repair involves disemboweling the rig to get the S logic board out removing a metal shield that covers the transistors about six solder connections and then replacing the surface mount transistor And of course reversing the whole process to put the rig back together again The part itself is cheap around 3 00 Feb 2002 If you re tempted to unsolder the control pots from the S Logic board stop and think you re probably doing things the hard way The affected transistors are on the side of the board facing the front of the radio More extensive mechanical disassembly will eventually gain you access Start by removing the front panel and work your way back Page 7 2 of th
8. what do do Ultimately you ll have to replace it either yourself or via Icom service It is possible battle field repair to free the contacts by tapping the relay till it frees but YMMV Actually it takes a fair amount od disassembly to access the relay and this solution is temporary at best 3 5 7 Where can I get an external switching relay You have several to choose from Ameritron ARS 702 Ameritron ARB 704 MFJ ARB 702 I MFJ ARB 704 W2ENY Amplifier Interface Yaesu FRB 757 Users of older amplifiers like the Heathkit SB 200 will want to check out the soft key modules from http www harbachelectronics com or a similar product the AmpKeyer at http www theheathkitshop com ampkeyer html Heil Sound makes a foot switch that can control both PTT and amplifier switching in the correct sequence http www heilsound com FS 2 Dual Footswitch htm KD9SV has a Front End Saver switchers that can handle extra antennas along with the amplifier Page 47 of 113 2003 02 08 IC 746 FAQ http www qsl net icom download fes pdf http johnjeanantiqueradio com gary htm You could build a very simple solid state switcher like http www gqsl net icom ampcontrol html http www qsl net dxlab Amp 20Control 20Circuit jpg 3 5 8 Can t I just use the ACC port to key my amp An Icom IC PW1 Yes Any other amp Not directly First off the signal from the ACC ports is from an internal transistor and w
9. 08 IC 746 FAQ Revision History 2002 11 26 2002 11 25 2002 11 22 2002 11 20 2002 11 19 2002 11 19 2002 11 19 2002 11 18 2002 11 18 2002 10 22 2002 10 20 2002 10 11 2002 10 08 2002 10 07 2002 09 30 2002 09 29 2002 09 28 2002 09 25 2002 09 23 2002 09 20 2002 09 15 2002 09 15 2002 09 09 2002 09 08 2002 09 06 2002 08 26 2002 08 20 2002 07 17 2002 07 15 2002 07 12 2002 07 12 2002 07 11 2002 07 10 2002 07 09 2002 07 08 2002 07 08 2002 07 07 2002 07 06 2002 07 05 2002 07 03 2002 07 02 2002 07 02 2002 07 01 2002 07 01 2002 07 01 2002 06 03 Added Q A on Quadra amp hookup Updated info on band decoders More info on researching rig prices More info on LCD repairs Added updated article information More info on CT 17 interfaces Added more info on RX TX receive line split Added another ham repair center More info on the Poor Man s TCXO Minor addition to band edge beeps More info on ignition noise Updated info on Icom HF net Added Q A about loose tuning shaft Added Q A about 2m S meter readings Corrected page number error in errata Added Q A on automatic external ATUs Added Q A about sticky switches Added Q A on finding repair shops Added Q A on TNC hookup Added Q A on CT 17 cable Several minor changes and link updates More info on power drop off Added Q A about low voltage operation shutdown More info on IC PW1 operation Added Q A about Alaska Emergency Frequency More inf
10. 14_omr pdf Here are a few interesting pieces of info from the datasheet Max Switched Voltage AC 120V DC 60V Max Switched Current 1A OMR F 0 5A OMR H Max Switched Power OMR F 50VA 50W OMR H 10VA 10W Max Switching Rate 300 ops min no load 30 ops min rated load Operate Time 1 0 msec Release Time 0 5 msec Expected Mech Life 100 million operations no load Expected Elec Life 1 million operations rated load First we see that the listed current voltage ratings do not match anything we ve seen or have been told before Curious that Why has Icom technical support given out at least TWO different sets of specs One theory is that the relay specs we have are still not detailed enough It turns out that there are two ways to report maximum contact current Maximum Switched Current is the maximum current at switching time when the contacts are opening or closing Once the relay is switched on the contact current may rise to as high as the Maximum Carrying Current but must reduce again prior to switching off Thus if the maximum carrying current is 2A then the answer from Feb 2002 could make sense Page 45 of 113 2003 02 08 IC 746 FAQ Switching Rates Explored Closer examination of the maximum switching rates reveals a possible problem Suppose for example I transmit at only 1 word per minute We average 5 characters per word 3 dit dahs per character and 2 swi
11. 2 100 hz 1 5 SSB Inrad 109 455 Khz 2 400 hz 1 6 SSB Icom FL 44A 455 Khz 2 400 hz 1 75 SSB Icom FL 96 455 Khz 2 800 hz 2 0 SSB wide Inrad 124 455 Khz 2 800 hz SSB wide Icom FL 257 455 Khz 3 300 hz SSB wide Notes The above specifications come from several sources so they might not be directly comparable Also there are always variations from one manufacturing lot to another Use these figures only as a guide Page 51 of 113 2003 02 08 IC 746 FAQ The Inrad 306 is listed on their WWW site and is electrically compatible but might not fit in the available socket The Icom crystal filters with an A suffix FL 44A FL 52A FL 53A all have 6mm lower case heights than the equivalent filters without the A Icom calls them low profile They are electrically identical to the taller filters Nobody knows if there is enough clearance to install one of the larger filters into an IC 746 There are apparently TWO slightly different FL 44A filters The earlier model has a slightly wider bandwidth and steeper skirts than the later model No word yet on how to tell them apart While not an optional filter W2ENY has a kit to modify the IC 746 by replacing either the stock 9Khz or 15Khz wide internal filters with a 6Khz wide filter See the mod question of the FAQ for more details 4 3 Which optional IF filters should I buy Better to ask Why would I even need filters Quite possibly you ll won t need any optional filters Use th
12. Australia that is limited to 20 8 watts on 2m for FM AM There are varying reports about the necessity of a microphone pre amp when using Heil microphones leading some to speculate upon differences in the microphone input circuitry K9HFX was unable to generate DTMF with an HM 14 microphone that might be related There isn t enough information yet to be conclusive Some rigs seem to have problems with the transistors that drive the LCD backlight while some do not This might be due to a circuitry change or a difference in assembly The jury is still out The only way the issue will be resolved conclusively is for someone to organize a data collection effort to sort out these details by serial number So far no one has volunteered 8 2 Can I operate 2m on reduced power Sure just turn down the RF output power control along the bottom front edge of the rig Too inconvenient Then you could get inside and tweak the pots that control the RF PA settings There are 4 of them for HF 6M 2M and AM R989 R991 R993 and R990 respectively Refer to your Service Manual for details 8 3 Where can I find plugs for the ACC connectors They are 7 pin DIN connectors the old style AT keyboards used 5 pin Din A couple of many possible sources are Digi Key http www digikey com BUX CommCo http www buxcommco com Your local electronics store probably either has them or can get suitable substitutes For example most Radio Shacks
13. NB is effective against ignition noise but not as effective as other rigs they ve owned Noise blankers are not all that sophisticated and will try to blank out anything that resembles an impulse even sharp voice peaks in an audio signal Sometimes the NB will generate more noise than it removes The IC 746 NB is operating within the first IF where the passband is about 15 Khz wide Any impulse like component of a nearby strong signal may activate the NB again possibly doing more harm than good Also strong nearby signals can fool the NB into fluttering the receive audio The single best way to deal with impulse noise is to eliminate it at the source A NB any NB is a compromise solution at best Page 76 of 113 2003 02 08 IC 746 FAQ 6 17 How do get rid of ignition noise Someone should write a book on this topic Oh wait someone did see below Here are some of the suggestions that have been made in the past e Clean the battery contacts e Run the power leads inside a grounded shield possibly an old coax braid e Add bypass capacitors to chassis at both ends of each power lead positive and negative e Ground the tailpipe to chassis e Ground the hood to chassis e Use higher quality plug wires Magnecor e Use better spark plugs Platinum is better that resistor Iridium is even better e Better quality copper inserts cap and rotor button e New radio suppression condenser at coil e Use PI network noise filter
14. While both are excellent supplies they just can t keep up with an IC 746 under full power The exact definition of intermittent peak or surge as used by the power supply manufacturers has not been established Some of us are trying to talk to the supply manufacturers about this to get more details To quote a tech from Samlex Maximum rating is surge current requirement for starting reactive loads or short term dynamic loading and is limited to a few seconds This supply is not designed for pulsing loads Currents beyond the maximum rating will force the unit into current limit and the output voltage will drop and it will no longer be regulated Meanwhile MFJ said of the MFJ 4322 Our units will shut down at surge At 25 amps surge the power supply will shut down at about ten seconds So while it is theoretically possible most people do not use supplies rated less than 20 amps continuous In fact most use substantially bigger supplies Bigger Supplies Why use a bigger supply There are several reasons As noted earlier the closer you operate a supply to its rated capacity the greater the electrical noise mechanical noise heat etc Strain leads to wear and tear So it can be argued that a bigger supply should last longer The IC 746 is rated at 20 amps max but loads as high as 21 22 amps have been measured Your mileage may vary definitely applies The continuous rating is generally based upon an ambient
15. about one paragraph While correct quick and immediate it will often gloss over subtleties and details The long answers will cover theory alternatives dissenting opinions and other supplemental material We try not to unnecessarily duplicate information between the answers this one is an example of that Long answers may go on for several pages The questions that are addressed here as well as the answers come from several sources This FAQ was originally created and hosted by folks on a Yahoo e mail discussion group at http groups yahoo com group IC746 Page 9 of 113 2003 02 08 IC 746 FAQ They have extensive information on the IC 746 including bookmarks and a file download area http www gth net hosts a more generalized Icom e mail list that covers all models not just the IC 746 You can lookup more information or subscribe to that list at http mailman qth net mailman listinfo icom There s a search engine for the above list but it s accessed from a Hallicrafters site at http www w9wze org Some of the info here originally appeared upon a bbs style on line discussion group that used to be at http vartel com icom746 icom746index html The site not been responding since Jan 2002 There are also the following newsgroups news rec radio amateur equipment news rec radio swap Specific comments or clarifications can be sent directly to the FAQ coordinator Content submissions would be gr
16. based presumably an op amp and yields about 16db gain for the 21 60 Mhz range 15m thru 6m bands In practice each HF preamp will work on any HF band The sensitivity of the IC 746 is so high that neither of the HF preamps are rarely needed You ll need the attenuator more often than the preamps Page 95 of 113 2003 02 08 IC 746 FAQ 8 15 How do I adjust the 746 for best AM performance The 746 performs well on AM for general communications However many operators choose and fall in love with AM for the sound For this the 746 can fall a little short of expectations Start by improving your audio fidelity as described elsewhere in the FAQ Then WUI1T Damon suggests that the trick is to back off the carrier level You don t want to run full carrier or full mic gain He also suggests turning compression off when using AM For general guidelines on setting up modern transceivers for AM use check out http www thebizlink com am tech htm plastic htm 8 16 Is the IC 746 suitable for CAP and MARS operation For CAP Civil Air Patrol use the IC 746 is compliant only for HF and then only if it has the CR 282 TXCO option installed It s not compliant on VHF at all See the following for more details http www ntc cap gov comm equipment hf_equipment cfm http www ntc cap gov comm equipment Lists cfm There s more information on this general topic at http www ntia doc gov osmhome redbook redbook html While I don t h
17. basics of the protocol are documented in the IC 746 Instruction Manual on pages 74 75 However most people will prefer the documentation available from DF4OR s WWW site at http www plicht de ekki civ or the documentation that comes shipped with W2ENY s control cables Page 61 of 113 2003 02 08 IC 746 FAQ http www geocities com w2eny civ http www geocities com w2eny icom_cable W7FG Vintage Manuals has listings in their catalog for both the CT 17 Level Converter and for the CI V Communications Interface on their WWW site at http www w7fg com 5 7 What is the CI V address of the IC 746 The CI V address of the 746 is 56 hexadecimal 5 8 What computer software is available 5 9 Where can I get computer software and upgrades There are several choices compromises available On one end of the spectrum we have programs that replicate nearly all of the IC 746 controls on the computer On the other end there are programs that do computer assisted contact and contest logging There is a fairly comprehensive listing of CI V compatible software on DF4OR s WWW site at http www plicht de ekki civ We ll mention some of the available software options below User reviews for some of the below software can be found at http www eham net reviews detail 1499 http www qrz com search pl topic reviews Icom RS 746 software Icom SELLS a program called RS 746 buying it is certainly the path of le
18. between mobile rigs Even Radio Shack has these cheap One very popular connector is the Anderson PowerPole http www andersonpower com which is readily available from either http www dcpwr com http www powerwerx com In fact the PowerWerx folks have pre wired PowerPole to OEM T cables ranging from 1 to 10 feet long that are much cheaper than the Icom part less than half the cost You can always just snip off the PowerPole connector if you don t want it Many clubs and organizations have been standardizing on the PowerPole connectors for their high amperage 12VDC power This makes all of their equipment inter compatible and interchangeable a real plus in an emergency There s a good article on that subject at http www dcpwr com standard html 8 8 Where can I get replacement microphone connectors You ve got plenty of sources Radio Shack P N 274 025 for the plug BUX CommCo at http www buxcommco com The RF Connection at http www therfc com micconn htm 8 9 What is Lo Fi SSB operation 8 10 What is Hi Fi SSB operation Trick questions as they are both the same They both refer to attempts to transmit receive higher bandwidth quality SSB signals Basically hams are trying to improve audio fidelity they are striving for Hi Fi quality Few if any SSB rigs will ever achieve the 20 Khz bandwidth normally associated with Hi Fi thus the Lo Fi pun Page 93 of 113 2003 02 08 IC 746 FAQ
19. breakers are required for UL certification Buy spare fuses right away they never blow at a convenient time Meters are non essential they are luxury items They make the supply bigger and more expensive However they can be very handy and even fun Lets face it most hams enjoy gadgets Adjustable output voltage is a useful feature more useful than you might realize Most new supplies have it usually internally Page 24 of 113 2003 02 08 IC 746 FAQ Load Capacity The size weight and cost of a power supply all tend to increase with its load capacity Those factors encourage us to get the smallest supply we can There are also factors that encourage larger supplies such as noise heat accessories etc The IC 746 specifications list a current drain at maximum transmit power of 20A at 13 8Vdc Thus the recommendation that your supply should handle 20 amps or more continuously It is possible to run the IC 746 with a smaller supply but extreme caution and discipline are required Very few if any of us recommend it for normal operation For example the 20 amp maximum in the IC 746 specifications is full key down at full power You could just lower your RF power to help match your load to the supply You could even run the IC 746 QRP drawing as little as 3 4 amps on transmit Another factor is operating mode Some of us have measured full key loads as high as 21 22 amps Normal SSB transmit at full power draws 6 15 amps
20. cssccssssccssscsssessesseeeees 77 How do I fix a loose rubber grip from the tuning knob ssccsssessseeees 78 Where should I go for repairs eessooessoessoesssesssocesoossooesosesssecssoossoossoosssosessese 78 How do I fix scratches on the LCD sccsscsssscsssscssscssssscssessssesssssssssssseess 80 What can I do about sticky switches cccscccscssscsssecssscccssssccssssesssesseseees 80 Why does the S meter seem low on 2m FM eesseeessoesssesssesssocesoossooossoosessesssee 81 Why is my tuning shaft knob loose and Sloppy sscscsscsssscesesscescseseseees 81 Why is my audio cutting in and out soesssessseossoossoossosesssesssesssoossoossosssssssssese 81 MODIFICATIONS viriai aaan aiara aa ana a aaan aaa anaana aaa Edain 82 What TX RX mods are there for the IC 746 e sesssesoossessoesoossessoesooesossoesooe 82 What other mods are there for the IC 746 eessessoesoosseesoesoossossoesoossossossooe 82 6Kh wide IF filters enais n n a a a a e ee 82 Safe 2m TX RX Sequencill Six oceno tis i a a a a aa a ia 83 Simple CAT interfase cie a aaa a AAR A RE EEan E 83 Separate 2m TX RX Antenna Lines s ssseseesseseseseeseesseserssressesrrssressessrssressessessees 83 Increased MONITOR Volume sseeeeesseseesseessessrsseesseesrssresseesesresseesesersseesseseess 84 Page 6 of 113 2003 02 08 IC 746 FAQ LCD Driver Transistor Replacement ccccesceseeeesceeseeceseceecesee
21. currents and hot switching usually get brought up as well as AC vs DC loading For years the topic keeps coming up but with no consensus or dependable solution except that using an isolation relay circuit seems to prevent any overloads Tech Support So many of us contacted Icom technical support Unfortunately we received different answers at different times For example in the icom qth net archives for January 2000 we see that tech support told AB2BK that there was a misprint in the manual The true rating was 12 Vdc at 20mA and Icom recommended an external isolation relay While that would explain the failures it makes some of the successes almost unbelievable On the other hand the archives for February 2002 show that tech support told N1JM that The real scoop is UP TO 16V OR UP TO 2 amps Again Icom recommended an isolation relay While the techs did not agree upon the ratings they did agree upon using the external relay Unfortunately none of the answers from tech support have adequately explained the odd successes and failures Service Manual All of this boils down to how much abuse relay RL1271 on the Main board can take The parts list on page 6 12 shows the relay as an OMR 109F The obvious solution is to look up the parts and see what they are rated for As of January 2002 nobody had revealed any spec sheets for the relay Internet Search Searching for OMR 109 on the Internet did turn up a curious tidbit Icom
22. excellent reputations particularly for out of warranty repairs or for older equipment MTS http www angelfire com biz2 mts Email mts plix com Malcom Technical Support MTS 3617 Deep Lake Boundary Rd Colville WA 99114 9142 Voice 509 732 8883 Fax 509 732 8884 Burghardt s http www burghardt amateur com Email hamsales burghardt amateur com service burghardt amateur com Burghardt Amateur Center 710 10th Street SW PO Box 73 Watertown SD 57201 Voice 605 886 7314 9 6 CST Fax 605 886 3444 W6XA Paul W Hansen W6XA 2411 Robert Nash Ct Tucker GA 30084 3325 Page 79 of 113 2003 02 08 IC 746 FAQ Phone 770 939 1320 Tim Moes Email temmoes yahoo com Watertown SD RadioWorld http www radioworld ca Email service radioworld ca 4335 Steeles Ave W Toronto Ontario Canada M3N 1V7 Phone 416 667 1000 Fax 416 667 9995 And of course you could always just run down through the list of authorized dealers at http www icomamerica com dealers index2 html 6 21 How do fix scratches on the LCD Short of replacing it you might try one of the following suggestions e You could try Polywatch which you might get from a local watchmaker note watchmaker not battery changer It s for restoring plastic watch crystals works great on them e If itis just an abrasion toothpaste or tooth powder might work or try body polish not wax for a car e For fine or hairlin
23. has used the OMR 109 before as the SEND relay RL2 in the IC 761 It had problems too There is a Service Bulletin 24287 001A entitled Larger relay for keying non ICOM amplifiers which recommends Replace RL 2 currently labeled OMR 109 on the PA Connector Board with a SY 12 relay ICOM P N 921 04696 This relay is larger but can be squeezed into place Glue this relay to the board with RTV For the full bulletins check out http www qsl net kd4sai mods icom ic 761 txt http www89405 temp w1 com Modifications B2502 Page 44 of 113 2003 02 08 IC 746 FAQ More searching did turn up information for the SY 12 K relay which lists a contact rating of 1 A 24 Vdc or 0 5 A 120 Vac resistive We can infer that the OMR 109 specs are most likely less than these http www fceu fujitsu com pdf sy pdf Unfortunately we still do not have many answers Contact Parts Supplers Finally in February 2002 we found a listing for the OMR 109F thanks to the kind folks at Omron Electronics for helping out It doesn t say much but does show a contact current rating of 1 A http catalog tycoelectronics com TE bin TE Connect C 14894 amp P 87296 91080 8 6600 76287 76437 amp M PROP amp N 1 amp LG 1 amp I 81 amp G G However the above link did show who the manufacturer is OMR relays are made by OEG That finally led to some actual data sheets http www oeg com cn pdf 14_OMR pdf http www qsl net kb9sss IC 746 Parts
24. http www kingsmith software com W2ENY W2ENY ships a CD ROM with lots of software and documentation along with the PC to rig interface cables he sells Many of the packages listed here are also on his disk http www geocities com w2eny civ http www geocities com w2eny icom_cable RadioComm Arachnophilia has several programs RadioComm IcomControl and EasyTuner among others Check out the download section on their WWW site is at http www arachnoid com YP Log Tony Field VE6YP makes a radio control and logging program called YPLOG that can control up to 4 rigs at a time and supports logging and contesting His WWW site is at http members shaw ca ve6yp TRX Manager Some say that TRX Manager by F6DEX has more features than the original radios More info can be found at http www trx manager com http www hosenose com trx manager Page 63 of 113 2003 02 08 IC 746 FAQ XMLOG The freeware logging software produced by W1ECT also talks directly to the IC 746 You can learn more at either the WWW site http www xmlog com or at the yahoo e mail group site at http groups yahoo com group xmlog TR Log One of TR Log s claims to fame is that it will run on just about any PC More details at http www gth com tr CI V Commander A package that integrates well with the DxLab software suite More details at http www gsl net civ_commander interface jpg IRC One of IRC
25. of the event Doug N7BNT located in Vancouver WA is usually Net Control and K C KG9JP in Phoenix AZ is usually helping out and hosting the chat room Page 14 of 113 2003 02 08 IC 746 FAQ There is usually a C746 chat room set up on Yahoo Internet Messenger Click on the Chat button go to Hobbies and Crafts click on the User Rooms tab and join in If you need a relay to check in to the net this is the place to go The chat room should be up about 10 minutes before net We ve heard of a few other HF nets devoted to Icom equipment in general They meet at Sunday 1700 UTC 14 315 Mhz ssb Sunday 2100 UTC 14 317 Mhz ssb 2 7 Are there electronic copies of 746 instruction manuals YES A PDF Adobe Acrobat format version of the IC 746 Instruction Manual is available on the IC746 Yahoo Group WWW site at http groups yahoo com group IC746 files IC 746 Instruction Manual Extra pdf This version of the manual has a full set of TOC bookmarks hyperlinks for all intra document page references and comment bubbles for all known errata During the first week of November 2001 Icom made an electronic copy of the original IC 746 Instruction Manual along with many others available on their WWW site at http icomamerica com support documents index html A backup copy of the above manual is available from several locations http groups yahoo com group IC746 files IC 746 Instruction Manual pdf http www gsl ne
26. on low RF output power More non 746 information links Add Q A on intermittent audio Minor trivial corrections additions too numerous small to list separately Added another article First rough draft in document format Started converting ASCII format to document format Page 2 of 113 2003 02 08 IC 746 FAQ Table of Contents ICOM IC 746 FAQ oa a scasaapuncasacansceaguansaasacensunenaanaanaaaaacananensunsaasaceuasenacaeveaes 1 RECENT CHAN GE S a a E se dacmcnatceaudadevenedenmendbenansedwdeceeedunyranssecetuennachs 2 TABLE OF CONTENTS a rrr ec soca rr Daaa ara ae aa a eea eea Eaa eee 3 1 ADMINISTR A cies tcscseccicesssatecesscececccccasivesixesaccctccsecssazesacasteccecusstetacasicesecde 9 1 1 What is an FAQ ccsictesscccccssscnsssaveleccessdessedevesescsesdspennaceseccessesseesesensdctess sgussevessactesses 9 1 2 Where can I Get a CODY vecssssssscsssccaucssostpscssoussecessisvnssbenpacsvoutbecsoseverseseeiseccsveseetanens 9 1 3 Where do I send feedback cccsccssscccsssecscseccssscecscscecssscecssssescessesssessesoesees 9 1 4 What are the future plans for the FAQ sssesssessseeesoossoossoossssesssocssoossoossssesssee 10 1 5 What questions still need to be answered ccsscccssscccssecsccsescssssscesseseees 11 1 6 What does this abbreviation or TLA mean e sseeesooesoossssessscossocssoossoossosesssee 11 2 GENERAL INF O E A 12 2 1 Should I Duy an IC 740 iiss sasoscsssspectvssonnsssnevdubvousssosssvevbu
27. per the IC PW1 manual The CI V set up will vary between the early and the latest IC PW1 units 3 Power on the IC 746 and the IC PW1 The IC PW1 should now automatically select the band the IC 746 is set to 4 Now start the software and set the software com port setting to the port you have the CT 17 connected to The software should recognize the IC 746 and show the exact frequency on the computer screen the IC 746 is tuned to 5 As you change bands on either the IC 746 or the software the IC PW1 will follow that band change If you change bands on the software both the IC 746 and the IC PW1 will follow that band change Paraphrased thanks to WAOSXV the procedure is e Turn everything on set the 746 to full power and key up in RTTY e Adjust the ALC pot on the back of the PW1 to set the IC PW1 ALC meter to the mid scale point Power out on the amp should now read around 500w if you are using 110 or 1000w if you are using 220vac No adjustments are needed on the 746 the PW 1 ALC should take care of that When properly adjusted the power output scale on the 746 will read something around 35 50w 3 5 2 What if I hook up more than just an IC PW1 The PW 1 manual claims that you will not have to mess with the CI V addressing That s not always true If the IC PW1 is directly connected to the IC 746 on default CI V address 54h and 56H respectively with no other devices then the PW 1 auto config routine senses the IC 746
28. the one ribbon connector lets you work on the front panel by itself as an assembly You can remove the S Logic Board by removing all the large knobs the tuning knob the tuning knob friction break and then two ribbon cables from the display board On removal of the tin lid on the shielding box housing Q302 it was obvious that this thing was getting HOT It had unsoldered itself from the pad under the collector and think this was the cause of the flashing as the collector was left floating decided to mount the new transistor vertically and add a small L shaped brass strip from the collector to the pad on the board in an attempt to keep it cooler removed the tin plate shield to enable this to be done and have some room to solder The part So far all reports from heftier transistor replacements have been positive From page 6 1 of the service manual we can see that Q302 is a2SB1201 At one point the folks at MTS suggested a 2SB1202 as a replacement Examining the specifications http www nedis com datasheets datasemi 2SB 2SB1201 pdf http www qsl net kb9sss IC 746 Parts 2SB1201 pdf http www nedis com datasheets datasemi 2SB 2SB1202 pdf http www qsl net kb9sss IC 746 Parts 2SB1202 pdf We can see that the suggested replacement is physically identical to the original part but with 50 higher current capacity and 25 higher power dissipation Its switching time is about 10 20 longer slower but that should be unimportant for
29. they are looking for an on line swap page There are of course plenty of other options Most dealers have used demo equipment Hamfests are a traditional favorite as are swap nets on HF That said the two largest forums on the internet for amateur radio gear are the USENET newsgroup news rec radio swap and the infamous eBay auction site http www ebay com Amateur Radio Trader is both a magazine and a WWW site devoted to amateur radio classifieds http www amradiotrader com site not responding Jan 2002 Yahoo has a small auction site as well http list auctions shopping yahoo com 23761 category html alocale Ous After those you have your choice of dozens of dedicated swap sites on the net A few of them are http www arrl org RadiosOnline http www grz com forum http www eham net classifieds http www k1dwu net hamtrader AC6V maintains an entire list of swap pages as part of his excellent ham links resoutrce site http www ac6v com swap htm 2 5 How much is a used IC 746 worth Unlike used cars there is no official blue book for ham equipment Only YOU can decide this Your best bet is to peruse the archives for news rec radio swap Page 13 of 113 2003 02 08 IC 746 FAQ over the past 6 months or so You might also check out one of the following sites Electronic Boneyard Prices http www geocities com CapeCanaveral Hall 8701 ham boneyard htm E Bay prices htt
30. this application K8UT has successfully installed a 2SB1202 replacement The Transformer In some cases the transformer is also fried Watch out for that when you make your repair otherwise you ll just blow the transistors again Further Analysis amp Possible Prevention WAOKWK observes that we appear to have a DC AC converter circuit with Q302 operating as a current carrying switch being turned off and on by Q301 a light dimmer When the backlight is dim the switch gets hotter because it is dissipating the current rather than the backlight When the backlight gets brighter more power is required by the display and the transistor has to sink less current by itself This leads to the counterintuitive deduction that brighter displays put less strain on the transistor than dimmer displays Thus the natural reaction turning down the display brightness actually makes the problem worse Page 72 of 113 2003 02 08 IC 746 FAQ While we can t yet prove the above assertion data compiled by WAOK WK from voluntary usage reports brightness level operation time problems and repair etc would seem to support the theory The raw data is at http groups yahoo com group IC746 database method reportRows amp tbl 2 Of course if your 746 is still under warranty you may want to consider going that route Either way you can contact Icom for the parts you need Alternate Prevention and Possible Field Repair AD6ZU Roy re
31. tips already provided on page 58 of the Instruction Manual Yes The ATU appears to pay attention to the reflected power not the SWR Note we d love someone to analyze the schematics to confirm or deny this This is evidenced by two effects When starting from a close match at QRP power levels the auto ATU doesn t always home in on the best match Increasing the power level and tuning again often improves the match which the ATU then retains when returning to QRP power In fact the manual mentions at least 8w on HF and 15w on 6m The converse situation can also cause trouble When starting from a poor match at full power the auto ATU sometimes can t find a match at all In this case tuning at lower power allows the ATU to get a match which the ATU then retains when returning to high power If one end of a band consistently gives you trouble while the other end tunes easily then you may still be able to coax the ATU into matching the antenna Start in the portion of the band where the ATU works and tune there Then move your way across the band in increments maybe 25Khz at a time tuning as you go until you reach the desired portion 3 2 6 Can use the internal ATU along with an external ATU Maybe Theory says yes but Icom says no The results are mixed Use at your own risk Page 29 of 113 2003 02 08 IC 746 FAQ Many people use an external ATU along with their IC 746 Usually they leave the external ATU switched to bypa
32. when the 9Mhz and 455Khz IF filters have closely matching bandwidths Non matching bandwidths will still work but are less intuitive which can cause confusion There are several techniques to using TPBT The one described below has the virtue of simplicity Page 55 of 113 2003 02 08 IC 746 FAQ Starting with both filters in their center detented position widest effective bandwidth and tune in your desired signal as accurately as possible Grasping both IF shift knobs simultaneously simply turn and adjust for the best sound If you have a nearby interfering signal then you ll probably have the best results shifting your bandpass away from it Now adjust just the 455Khz IF shift the inner knob in the opposite direction for the best sound There s a whole document describing the theory and mechanics behind TPBT at http groups yahoo com group IC746 files ic746_tpbt txt 4 16 How do configure the IC 746 to use an optional filter After you ve installed a filter you need to tell the radio about it Using the SET menu tell the radio which filter you ve installed by Icom part number and which slot it is in Then hold in the FILTER button for two seconds to bring up the filter selector Cycle through your available filters by mode and by wide narrow until everything is set up the way you want See the operator s manual for details 4 17 How do configure the IC 746 to use a non Icom filter You have to lie to the ri
33. wire up the IC 746 for use with PSK31 oesssesssoesssessseossoossosssoo 65 Why isn t my computer control working eessoesssesssesssocesoossoosssoossssesssesesoose 65 Page 5 of 113 2003 02 08 6 1 6 2 6 3 6 4 6 5 6 6 6 7 6 8 6 9 6 10 6 11 6 12 6 13 6 14 6 15 6 16 6 17 6 18 6 19 6 20 6 21 6 22 6 23 6 24 6 25 7 1 7 2 IC 746 FAQ PROBLEMS AND CLARIFICATIONG cccccccceeeeeseeeeeeeeeeeeeeeeeeeneneeeees 66 What s that funny rattling noise I hear when I first power on 0000 66 What s that click I hear as I tune across certain frequencies 006 66 Why doesn t the ALC meter work while adjusting the mic gain 66 Why can t I set numbers into memory names CW Keyer etc seseeees 66 Why isn t my output power up at 100 watts eeessoessoesssesssesesoossoossssssssesssese 67 Low DE supply y ltag nr nrnna aaa A a AA A R 67 You have an IC 746s instead of an IC 746 s sneneesseessesssseessessresresseesreseessreseese 67 Bl wn Internal FUSC ncen nenen ei a e a a E S 67 The RF driver transistors may have failed six s asiiccieladistecdiccacd sacdebadersseddasiates 68 The RF power amplifier transistors may have failed ee ceeeeseeeeeseeeeeeeeeeeees 68 Blown Output Detector DiGdes 2505 osu gasses Ses ae oes ade set ocanes essed eV onceeass ras tate 68 Your ALC circuit may have tated astute tales miae ica eiwees 68 SW POld Dak a istects
34. 1 What antenna should I use with the IC 746 Short Answer Any antenna you want Long Answer Seriously ANY antenna will work with the IC 746 with the proper interfacing People have even made contacts using dummy loads Antennas are probably the most uniquely individualistic aspect of any ham station Antenna selection is a BIG topic much too big to deal with in an FAQ at least for this one The IC 746 has 50 ohm unbalanced coaxial RF outputs With the automatic ATU capable of handling SWR mismatches of up to 3 1 on HF and 2 5 1 on 6 meters you have a wide variety of choices available to you There are many excellent books on the topic the ARRL has a couple dozen of them A good one to start with is The ARRL Antenna Book At over 800 pages and over 1 000 antennas you re sure to find SOMETHING that fits your style and budget For more information try hanging out on one of over 50 e mail groups on the topic at http groups yahoo com group IcomRadio or visit one of the hundreds of antenna oriented WWW sites indexed by AC6V http www ac6v com antprojects htm http www ac6v com antprojects htm or follow along with the discussions on the newsgroup news rec radio amateur antenna or visit the on line antenna magazine http www antennex com or you could just put up a trusty old dipole Just be sure you do use an antenna The IC 746 does not like to transmit into an open load no connected antenna I
35. 2 grains of sand To replace the parts requires a very small tip soldering iron a fine tipped pair of tweezers and a very steady hand What did was to use some solder wick to remove much of the solder was then able to remove the parts with reasonable ease Just as a warning when changed mine out once the solder joint released my D9 when flying never did find it Lucky had already ordered spares If you re brave enough to try it I ll wish you the best of luck and add that give no guarantees that this will fix your rig but it did fix mine 3 2 18 How do I switch between more than two antenna ports With a switch of course Actually you re probably looking for an automatic way to switch between different antennas based upon your current operating band For that check out Automatic Antenna Amplifier Selection by Band mods elsewhere in this FAQ Page 35 of 113 2003 02 08 IC 746 FAQ Page 36 of 113 2003 02 08 IC 746 FAQ 3 3 Microphones 3 3 1 What is the best microphone to use with the IC 746 In theory your favorite microphone is the best choice provided you hook it up and adjust it properly Its basically just a matter of personal preference The confusion lies in the definition of best Most users generally agree that the stock hand mic is generally adequate for general use but is not best or optimal for any specific use You know the tale jack of all trades master of none If you want bett
36. 3 of 113 2003 02 08 RIT RTTY RX SSB SWR TCN TCXO TPBT TS TX USB VFO VOX IC 746 FAQ Receiver Incremental Tuning Radio TeleTYpe short for Receive or Receiver Single Side Band Standing Wave Ratio Tone CoNtrol SSB transmit cutoff Temperature Compensated crystal Oscilator Twin Pass Band Tuning Tuning Step short for Transmit or Transmitter Upper Side Band Variable Frequency Oscilator Voice Operated transmission YMMV Your Milage May Vary standard disclaimer Page 104 of 113 2003 02 08 IC 746 FAQ Contributors Acknowledgements There are two kinds of contributors to this FAQ direct and indirect Direct contributors have written entire passages that have been incorporated nearly verbatim Sometimes they are specifically authoring something with the FAQ in mind Also they are individuals who have been recruited to review specific sections prior to distribution Indirect contributors have had their comments and input collected and assimilated from public correspondence on discussion and news groups often without their knowledge They were simply answering questions offering advice or otherwise just helping people out The coordinator has not tried to keep a record of who has contributed what the book keeping would be horrendous All sources of information have been INVALUABLE and are APPRECIATED Listing contributors here is a small token of thanks for their neighborly spirit and generosity The Coordin
37. 746 FAQ Page 53 Enter numbers via keypad not tuning dial While the diagram specifically highlights the numeric keypad on the radio the instructions fail to mention that numbers and the decimal point are entered via the keypad instead of the tuning knob Page 56 Incorrect Page References In the Ist paragraph the reference for programming scan edges is p 56 but should be p 52 Page 68 Unclear Voltage Specification The box describing the ALC JACK lists an input voltage of 0 4 V It should read 4 to 0 Vdc Page 70 Overoptimistic SWR Specification In the box labeled ANTENNA SWR the manual states in part When the SWR is higher than approx 2 0 1 the transceiver s power drops to protect the final transistors Actually power starts cutting back much earlier than that somewhere between 1 7 1 and 1 3 1 Page 77 Unclear UT 102 Installation Instructions The UT 102 Voice Synthesizer is installed in the bottom of the transceiver not the top Also the shield cover is not involved Page 79 Incorrect SEND Relay Specifications The NOTE for CONNECTING A NON ICOM AMPLIFIER should read NOTE The specifications for the SEND relay are 12 V DC at 20 ma milli amps If this level is exceeded an external relay or switching transistor must be used The 746 SEND line is designed to interface to a solid state amplifier trigger like those used in Icom s power amps Many people have damaged their rigs by trying to switch
38. AQ 2 12 What is the IC 7400 2 13 What is the IC 746 PRO These are both successors to the IC 746 The IC 7400 is the Japanese version while the IC 746 PRO is the English version We don t know yet what else if anything differentiates them besides their name There are two ways to look at the IC 746 PRO Some view it as a beefed up IC 746 while others view it as a watered down IC 756 PRO On the outside it looks and operates very much like the IC 746 The controls are similar enough that you confuse the two However the inside RF chain and DSP is more like the IC 756 PRO than anything else Here are some features that the IC 746 PRO has over the IC 746 e 32bit DSP with 24bit ADC e Selectable digital filters 50 e Sharp or Soft filtering via DSP e Digital TPBT e Manual digital notch filter in addition to ANF e Twinned Digital APF great for RTTY e DSP based RTTY decoder e Adjustable digital noise blanker e Digital TX RX equalization instead of analog e Digital speech compressor instead of analog e Digital voice recorder You ll notice how prominently the DSP plays in this rig One thing the original 746 has over the 746 PRO is an additional IF stage thus its TPBT is actually going through two offset IF filters The 746 PRO achieves its TPBT via the DSP It is argued that the DSP filtering more than makes up for the lack of the extra filter and is more programmable flexible It is counter argued that DSP filteri
39. Added Q A on birdies Added info about QTH NET s ICOM e mail list pdated Q A on IC 7400 dded Q A about beverage antennas Fixed numerous spelling errors Updated Q A on ATU to reflect recently reported damage Added Q A about IC 7400 IC 746 MKII gt g pdated info buying a 746 pdated info on accessing the FAQ Jpdated Q A on ATU range pdated Q A on ATU tricks band sweeping Added Q A about reset to factory defaults Crea SG Added Q A on VOX and ACC 1 Reorganized into sections with contents Added Q A on Receive fidelity Updated info on different versions of IC 746 Updated info on computer control Updated many Q A on IF filters Added Q A on ACC DIN connectors Changed Q A to ATU tips high power Added several Q A on band edge beeps Added many Q A on IF filters More info on computer control software Added disclaimer amp copyright notice More information on power supplies Added Q A on ATU at QRP power Added Q A about low output power Added Q A about Heil microphones Added Q A on wiring up keys keyers More information on power supplies Added multiple Q A on computer control Added Q A about different versions of IC 746 Page 112 of 113 2003 02 08 2001 05 25 2001 05 24 2001 05 23 2001 05 22 2001 05 21 2001 05 20 2001 05 20 2001 05 19 2001 05 18 2001 05 17 2001 05 16 2001 05 15 2001 05 14 2001 05 01 2001 04 20 2001 04 02 2001 04 01 IC 746 FAQ More information on power supplies Added Q A
40. IC 746 FAQ Icom IC 746 FAQ MP W gt MPR 3 Tx S Fi HC JC F2 F3 4 JOC FS Gem UC SSB ee AMG Gum iG j 0 0 0000 MOGAN RFPWR CWBITCH KEYSPEED PAMPIATT NB VOXBKIN MONTOR Frequently Asked Questions About the Icom IC 746 HF VHF Transceiver Coordinator Dana Hoggatt KB9SSS kb9sss arrl net Copyright c 2001 2002 2003 by Dana Hoggatt all rights reserved Page 1 of 113 2003 02 08 IC 746 FAQ Recent Changes 2003 02 06 2003 02 06 2003 02 06 2003 02 05 2003 02 05 2003 02 04 2003 02 04 2003 02 04 2003 02 03 2003 02 03 2003 02 02 2003 02 02 2003 02 02 2003 02 01 2003 02 01 2003 02 01 2003 02 01 2002 12 04 2002 12 03 2002 12 03 2002 11 29 Added another QST article to the article list Added current vs voltage chart to power supply section Added Q A on zero beating CW signals Added info on annotated copy of IC 746 Instruction Manual Added info on an Italian copy of the IC 746 Instruction Manual Added another SEND amp interface Added another microphone pre amp circuit Added a Q A about circuit schematics Added a Canadian repair center More info on LCD scratch removal Added ACC 2 pin out diagram Added ACC 1 pin out diagram Added MIC pin out diagram Added errata about receiver selectivity Added extensive info
41. JKC Keith Carter Canada VE4HAY Derek Hay Canada NOAT Ron VE6CGX Tony Hwang Canada NOGMP Dave VETMDL Erik Canada NORC Rod Cerkoney VE9FX Lin Canada NOUK Chris C VK4ZSS Sam Canada NIEGE Steve N1JM John Merrill WOLSD Ken NILF Les Rayburn WO0QE Larry Benko N1ZQU Sean WOTLO John N3JJA Jim Nuytens WOTUP Arlon N N4AIW Fred WO0VD Dan N4TJ Tom Johnson WIIK Jim Wickstrom N4UMJ Eddie Bryant WIMCE Dave S N4WMX Robert WIMNK Jon N5NW Marty W2ENY Bob Langston N5PHT Gary Stone W2MAW Mark Wolf N6TGK Stephen M W2VJN George N7DLS Dan Skaggs W3UHF Frank Ellis N8AVX Jim W4LT George N8GJ Jerry W4RNL L B Cebik N9IRD George W4RRY Leo L N9ORLA Dan Evans W4UGM Richard Cash NI9Y Dan W4UK Jerry NT7S Jason Milldrum WS5UN David Blaschke NX1G Steve Jones WS5YR George NY2H Warren WoCCD Dick W6OLD Dick Flanagan OK2WY Jiri Holy Czech Republic W6RCA Cecil Moore W7DGX Rolly OZIEQC Per Bekker Madsen Denmark W7SAC David McCallum OZS5ACI Frank Tjoernelund Denmark WS8DBF Duane Fischer W8EFN Randy Farmer P40GH Jerry Aruba W8JN Paul W9IFCC Dan McKenzie PAOJED Jan E Netherlands W9IFS Jerry PAOWCA _ Wim Bovendeert Netherlands WILVC Frank PE1OGF John Peters Netherlands W9INHQ Bill W9ISWL John Ingersoll S56AL Aleks Slovenia WAO0KWK Larry Boyler WAOSXV_ Mike SM4FPD Roy N Sweden WAIVTA Tom Loebl WA2FAA _ Jim Sutkoff SP5QIP Mike Poland WA2EHZ Larry Lefezik WA2TTI Jerry Harley TF3KX Kristinn Iceland WA2TTP Steve WA4TUK Patrick T VA3LGD Lawrence C
42. Q A about low power 2m operation Updated info on power output vs input voltage Page 111 of 113 2003 02 08 2001 10 30 2001 10 24 2001 10 24 2001 10 23 2001 10 23 2001 10 22 2001 10 21 2001 10 20 2001 10 19 2001 10 18 2001 10 18 2001 10 17 2001 10 16 2001 10 15 2001 10 15 2001 10 14 2001 10 12 2001 10 09 2001 10 05 2001 10 01 2001 09 21 2001 09 21 2001 09 06 2001 09 05 2001 09 01 2001 09 01 2001 08 28 2001 08 14 2001 08 07 2001 08 07 2001 08 07 2001 07 25 2001 07 20 2001 07 19 2001 07 18 2001 07 09 2001 06 30 2001 06 28 2001 06 27 2001 06 26 2001 06 26 2001 06 22 2001 06 12 2001 06 12 2001 06 12 2001 06 12 2001 05 30 2001 05 30 2001 05 29 2001 05 28 2001 05 27 IC 746 FAQ Added Q A on IC 746s Added Q A on multiple keyers Started a small glossary Clarified Q A about Heil mic adjustments Added Q A about dynamic microphones Updated info on different versions Added info on ACC pin outs Added info on Sunday evening 20m IC 746 net Updated info on mods Added Q A on transmitting less than 5 watts Added Q A on internal ATU while receiving Added Q A on finding Mic connectors Added another mirror site at qth net Changed all newsgroup references into links Added Q A on where to buy sell a used IC 746 Added Q A on other Icom rigs 756 765 735 etc More info on internal external ATU interactions Updated info on internal external ATU interactions Added Q A on computer interfacing
43. QST p 78 Solving Sound Card Microphone Problems Covington Michael A N4TMI June 2000 QST p 61 Shows a tiny phantom powered microphone preamp Automatic Amplifier Selection for the ICOM IC 746 IC 736 and IC 706MKII Transceivers Hewitt Paul WD7S May 2000 QST p 33 Operating via the ACC connector thus bypassing the SEND relay this project provides automatic amplifier keying with ALC selection based on the Icom band signal An External Amplifier C ontrol Circuit for the IC 706 MK2 Hauff Fritz W3NZ September 1999 QST p 80 Hints Kinks The IC 706 and IC 746 have nearly identical external amplifier interfaces issues so most of the information is relevant A Direct Frequency Entry Keypad for ICOM Transceivers Hansen John W2FS December 1999 QST p 38 Adds an external keypad via a PIC and CI V ICOM IC 746 MF HF VHF Transceiver Product Review Wolfgang Larry WR1B September 1998 QST p 70 Page 20 of 113 2003 02 08 IC 746 FAQ A product review article http www arrl org members only prodrev pdf pr9809 pdf Der Neue von Icom IC 746 mit 100w und DSP auf 11 Bandern Petermann Bernd DJ1TO April 1998 Funkamateur p 392 A product review article German A Remotely Controlled Antenna Switch Thompson Nigel KG7SG April 1993 QST p 32 Uses the band signal on the Icom ACC connector to remotely switch between antennas with a single feedline This article predates the 746 bu
44. R between the tuner and the antenna The external meter should always read greater than or equal to the meter in the 746 It s actually possible to match your rig to your antenna by simply changing the length of your feed line For an extreme but very workable example check out http www qsl net wSdxp notuner htm This is not to say that the internal SWR meter is accurate Posts that suggest that the internal SWR meter reads lower at lower output power than at full output power The effect is noticeable but not pronounced 3 2 16 Which SWR meter should I trust internal or external Both can be trusted but tune by the internal meter You probably care because you are using an external ATU Tune to bring the internal meter to a minimum reading Its the meter that tells you how happy your RF power transistors are and whether or not you re suffering SWR power foldback Page 34 of 113 2003 02 08 IC 746 FAQ 3 2 17 How do l repair the detector diodes in the internal ATU Mike describes his experience at fixing blown detector diodes in the internal ATU The problem was that the Auto Tuner would no longer tune up the antennas that it used to for me and the SWR didn t change on the antennas as measured by my MFJ 259 antenna analyzer It would either try for 6 10 seconds and then drop out or try for only one or two seconds and drop out When it dropped out the Tuner indication would go away on the display Rather than sendi
45. U is on Do not change frequency while the ATU is searching for a match 3 2 7 Does the internal ATU work on receive Yes The internal ATU is enabled while receiving Of course it can only match while transmitting It s unclear if the internal ATU acts as an additional preselector when enabled 3 2 8 Any other gotchas with the internal ATU We ve already mentioned above the possible hazard of using the internal ATU and an external ATU at the same time We ve also mentioned above that operating the internal ATU at the limits of its abilities might overtax it over time Page 30 of 113 2003 02 08 IC 746 FAQ A possible problem we haven t already mentioned may stem from the possible similarity between the IC 746 and the IC 756 The IC 756 users have been warmed not to use either their Auto Tune or PTT Tune features while on 6m even the manuals mention this although in passing Several have damaged their internal ATUs this way causing them to get stuck in 6m operation after damaging the relays It has been speculated that some of the reported mishaps with the IC 746 internal ATU with 6m may be related It s not hard to imagine that the 746 756 share a common ATU design We d appreciate someone with access to both service manuals doing a detailed circuit comparison to confirm refute this Finally the internal ATU is only matching at the internal PA You ll still have high SWR out on your coax as expected 3 2 9 Ho
46. Usually you don t Measuring SWR requires a signal The only way to get a signal on SSB is to modulate i e you talk Page 31 of 113 2003 02 08 IC 746 FAQ The simple thing to do is to switch modes to either AM or RTTY briefly After making your measurement switch back to SSB 3 2 12 How do l tune up in CW without a key Usually you don t You probably don t even want to be in CW mode without a key Odds are you re trying to tune up for a different mode for example PSK on SSB The simplest thing to do is switch briefly to AM or RTTY and tune there If you insist upon tuning up in CW without a key then you really only have one option simulate a key You could turn on the mic keyer which uses the scan buttons UP DN operate the keyer Or you could wire up a dummy key jack and key the rig by plugging the dummy jack in and out There s even one ham who uses his headphones as a dummy key but very few of us are willing to take that risk 3 2 13 What about using an external automatic ATU There are many automatic ATUs you could use Your choice boils down to two basic questions Do you want to tune at the antenna or in the shack Do you want an Icom tuner or a third party tuner Tuning at the antenna is far more efficient than tuning in the shack feedline SWR etc however tuning in the shack is more convenient no power or control cables Icom tuners will be plug n play with the IC 746 while third party tuners may re
47. a coupler intended to tune random length wire and whip antennas The AH 4 is mounted at the antenna and the RF lead from the coupler to the radiator should be as short as possible The AH 4 covers 3 5 to 54 MHz continuous with a 7m 23 ft wire antenna Here is the AH 4 brochure http www icomamerica com support documents brochures ah 4 pdf And a very informative site on the AH 4 including an AH 4 FAQ http www hamoperator com ah4 ah4 htm AH 3 The AH 3 is an older out of production alternative to the AH 4 it covers 1 8 to 30 MHz continuous with a 7m wire antenna There is info on it at the following WWW site http www qsl net n4pl ah3 AH 2 Older still the AH 2 could cover 1 8 to 30 MHz with a 12m antenna or 3 8 to 30 MHz witha 3m antenna 3 2 14 Can the TUNER button activate an external automatic ATU Yes The IC 746 has a connector designed to directly connect to the Icom AH 4 automatic antenna tuning unit Page 80 in the instruction manual describes hookup and operation Once installed pressing the TUNER button for 2 seconds will cause the rig to transmit 10w in CW mode until the AH 4 finishes The IC 746 assumes that the AH 4 is connected to ANT 1 and automatic tuning will only work there ANT 2 is still available but with no ATU In fact there s a whole WWW site devoted to the AH 4 Check it out at http www hamoperator com ah4 ah4 htm Most Icom tuners use the same interface AH 2 AH 3 AT 180 etc
48. about DTMF tones Added Q A about numeric programming Added Q A about antennas Added Q A about electronic manuals Updated info on rig modifications More info on power connectors Dayton Hamvention WooHoo Updated info about an Icom HF net Added Q A about non SSB ALC readings Added new info about an Icom HF net Added Q A about broken LCD backlight More information on power supplies First circulated copy First rough draft Started collecting notes Decided to make FAQ Page 113 of 113 2003 02 08
49. about the C 746 cssccsssscscsssesceeseseees 19 2 17 Can I transmit 100w at 100 duty cycle on CW SSB RTTY PSK etc 21 2 18 I thought the LCD was blue but photos show it as green sccccssesseeees 22 2 19 Can the IC 746 work on the 60m band seosseosseossoossoossoossssssssesssoossoossosssose 22 2 20 Can the IC 746 work on the Alaska Emergency Frequency ss0sesseeee 22 3 ACCESSORIES a eee are ee 23 3 1 POWER SUPPLIES a a aaae a a aaa eee raa e Ea apa 23 3 1 1 What power supply should I use with the IC 746 sessseossooesoossooossoossssesssee 23 Continuous vs Intermittent Load s sssseesseeseeseosseeseesessseesesressseserssrossessessresseese 25 Page 3 of 113 2003 02 08 3 2 3 2 1 3 2 2 3 2 3 3 2 4 3 2 5 3 2 6 3 2 7 3 2 8 3 2 9 3 2 10 3 2 11 3 2 12 3 2 13 3 2 14 3 2 15 3 2 16 3 2 17 3 2 18 3 3 3 3 1 3 3 2 3 3 3 3 3 4 3 3 5 3 3 6 3 4 3 4 1 3 4 2 3 4 3 3 4 4 3 5 3 5 1 3 5 2 3 5 3 3 5 4 3 5 5 3 5 6 3 5 7 IC 746 FAQ ANTENNAS aaa a ae ioc stetaecestotaecetlacsnaabitaniesecdanmustetoeveshotieaeatans 28 What antenna should I use with the IC 746 ssessseessesssocesoossoossssesessesssesesoose 28 What range can the automatic antenna tuning unit ATU handle 29 Will the internal ATU handle random wire antennas eesssessessessoesoossessoee 29 Will the internal ATU handle long wire antennas e sseeesooesooss
50. adable even when an overly narrow filter has rejected part of the desired signal That s where our advantage comes from One form of interference is when a nearby signal overlaps your desired signal as in an overcrowded band Rejecting the interfering signal necessarily rejects part of the desired signal as well Thus the filter is too narrow to allow all of the desired signal to come through but it is narrow enough to reject the interference While the result is distorted in comparison to a clean signal it is still more readable than if you left the interference there Another example would involve CW or PSK31 The more narrow the filter is the less the interference and noise In these modes it s almost impossible for a filter to be narrow enough to actually reject part of the desired signal as in the previous phone example Instead when a CW PSK31 filter gets too narrow you start to experience the auditory equivalent of tunnel vision This can make it difficult to scan around for signals One of the handy things about TPBT is that you can narrow your effective IF filtering bandwidth at any time 4 10 What s the difference between IF filters from Inrad vs lcom Inrad filters tend to have a superior shape factor to Icom s smaller numbers are better as well as deeper stopbands They also tend to be cheaper When dealing with adjacent channel interference the filter shape depth and slope of the attenuation curve is generally the p
51. ade the radio cheaper 4 20 Any tips on installing 9Mhz Inrad filters Neatness counts Good soldering skills are a must Most of the hams who have installed one report that it was more time consuming than they expected but nothing they couldn t handle KESDC says Inrad also ships two socket pins that look like they are to be used for the filter This doesn t work as with the pins on the filter the filter won t fit in between the case and the fan Solder the leads etc directly on the filter pins and then trim the pins to prevent grounding My first attempt the pins had poked through the electrical tape and grounded to the case It initially seemed like the filter was more effective than it should have been Some playing around with the filter settings while listening to a decent signal narrowed down the problem to the 9MHz filter and just redid it and it worked 4 21 Where do l install a 2nd Inrad 9Mhz IF filter According to K7ZL the place Inrad tells you to put the first filter is way over on one side in a little opening next to a fan and that works fine But he has found a second location When you have the rig opened if you go on a line from the 9 Mhz filters then to the 455 Khz filters and keep on going towards the front panel you will see a square metal plate on the circuit board He mounted his second filter on top of the metal plate on its side and it seems to work fine However KE5DC reports that is very difficult t
52. air temperature of 20 C The rating degrades as the temperature rises but by how much we re not sure Filed Day conditions will be stressful to your supply 13 8 V times 20 A yields 276 watts There s a tendency for some supplies to drop voltage a little when they get hot or overloaded There s also a tendency for some radios to increase their current pull when the voltage drops At 12 Vdc that same 276 watts would imply 23 amps You push the supply capacity which drops voltage a little which drives the rig current up which pushes the supply further then BANG You blow a fuse AK6R has actually seen this effect with his 756pro There are plenty of other devices that need DC power You need to account for them as well Page 26 of 113 2003 02 08 IC 746 FAQ Other and future rigs may have greater power demands like the 756pro Extra capacity now may avoid the need to upgrade your supply in the future You might well spend most of your time in a low power situation SSB QRP and get by with less than 5A But in an emergency you and your gear may be called upon to operate in different modes at higher power and with heavier duty cycles Planning ahead for the worst case usage helps prevent an untimely failure at just the wrong time Conclusion So you ll find most of us with power supplies ranging from 20 to 30 amps continuous and some with even bigger supplies Page 27 of 113 2003 02 08 IC 746 FAQ 3 2 Antennas 3 2
53. amplifiers with higher voltage current requirements Page 84 Incorrect Bandwidth listing Under Receiver Specifications the USB LSB CW Selectivity is listed incorrectly as 2 1Khz The actual selectivity bandwidth is determined by the IF filter selections By default as shipped the selectivity bandwidth for those modes is 2 4 Khz Page 101 of 113 2003 02 08 IC 746 FAQ Service Manual Discrepancies The Service Manual is supposed to be the best final word on the electronics within the IC 746 However the data it contains isn t always consistent Here are the known discrepancies Identity of Q302 Q302 on the S Logic Board is a driver transistor for the LCD backlight It s listing varies depending upon the reference within the Service Manual We d love to hear which part is actually in your rig p 6 1 Parts List 2SB1201 S TL p 8 1 Semiconductor Information 2SB1201 S p 10 1 Block Diagram 2SB1202 p 11 2 Voltage Diagram schematic 2SB1201 We believe the part is supposed to be a 2SB1201 Identity of R1271 R1271 on the Main Board is a dry reed relay for switching the SEND signal used to operate external RF power amplifiers It s listing varies depending upon the reference within the Service Manual We d love to hear which part is actually in your rig p 6 12 Parts List OMR 109F p 11 4 Voltage Diagram schematic AHY 103 The Board Layout on page 9 7 clearly shows that the R1271 has a completely different layout than
54. an pull a connection loose or cause a short circuit nothing will burn out you ll just lose the communications and start pulling your hair out When you complete the interface if it doesn t work recheck your connections and follow the schematic again The design REALLY DOES WORK Most likely there was a mistake in the soldering You can also purchase many renditions of these hardware interfaces from a variety of sources Universal RS232 Serial Interface for Icom Yaesu http www butel nl icomr2 icom1 1 html K1NU ICOM Computer Control Interface http home att net k 1 nu k 1 nu Products RTS 01 Computer Interface cable for Icom HF Radios http rtsars com othercables_template cfm http www sarrio com sarrio wlgee html 5 4 Do I need a special cable to connect a CT 17 to an IC 746 No the cable is a simple 2 wire cable with a 1 8 miniature phone jack on each end When homebrewing some folks don t even bother to shield the cable and just use a twisted pair 5 5 What is the control protocol for the IC 746 5 6 What is CI V CI V is the control protocol used by ICOM for remote PC control of their equipment This feature was originally used to enable a separate transmitter and receiver to act as a transceiver when interconnected via the CI V bus the receiver acts as a slave to the transmitter s QSY and mode change reports and for external amplifier control It was only natural to adapt it to computer control The
55. an two antenna ports ssccsscsssesees 35 MICROPHONES opein in a aa oea e anaa e aa a ro a ae iaa 37 What is the best microphone to use with the IC 746 e essesssessossessoesoossossoesooe 37 Can I hook up a different microphone directly to the IC 746 ss00e 37 Can I use a Heil microphone with the IC 746 ccsssccssssecsssecssseseseeesenes 38 How do I adjust the IC 746 for a Heil headset ccsscccsssscssssscscseseseeeees 38 Do I need a pre amp to use a Heil microphone sccsssccsscsssecssssssssseees 38 What are the pin outs on the microphone connector sessecssecsserssseees 39 KE YE RS a a a aaa a cee 40 Can I hook my straight key to the front Elec Key Jack sscsscssssessees 40 Can I connect my own Electronic Keyer to the IC 746 e sessesseesoessossossoessosse 40 How do I wire up my paddles for use with the internal keyer e seseseseseessee 40 FOR A STRAIGHT KEY OR EXTERNAL KEYER eeesseesesssesseseesseseesesse 40 TO USE THE BUILT IN ELECTRONIC KEYER WITH PADDLES 40 Can I use the internal and external keyers at the same time cccsseeee 41 AMPLIFIERS r T eo cee r te 42 How do I hook up an Icom IC PW1 RF power amplifier ccssssssseeee 42 What if I hook up more than just an C PW1 csscssssssscssresssossessseeeees 42 How do I hook up a non Icom RF power amplifier sccccscccsssessseeees 43 Do I
56. anada WA6PX Jim Shaw VA7JWR Jan Reimers Canada WB2CPN Clete Whitaker VE2MHF Francois Canada WI3X Dane Burns Page 106 of 113 2003 02 08 IC 746 FAQ WN2SQC Ken SVIENS 2 Greece WUIT Damon C Mike Foerster If anything then the sheer number of people involved more than 100 contributors from more than a dozen countries should illustrate the collaborative effort involved in producing this FAQ Thanks to everyone involved Page 107 of 113 2003 02 08 IC 746 FAQ Disclaimer amp Copyright This article is provided as is without any express or implied warranties While effort has been taken to ensure the accuracy of the information contained in this article the author and contributors assume no responsibility for errors or omissions or for damages resulting from the use of the information contained herein Use at your own risk Copyright c 2001 by Dana Hoggatt all rights reserved This FAQ may be posted to any USENET newsgroup on line service WWW site or BBS as long as it is posted in its entirety and includes this copyright statement This FAQ may be distributed as class material on diskette or CD ROM as long as there is no charge except to cover materials This FAQ may not be distributed for financial gain This FAQ may not be included in commercial collections or compilations without express permission from the author Page 108 of 113 2003 02
57. and everything works just fine Page 42 of 113 2003 02 08 IC 746 FAQ If you introduce additional devices or alternative interfaces such as the DX4WIN logging software using the 10 Radio Shack interface talking to the IC 746 in CI V address 56H then the PW 1 can become confused and stop talking to the IC 746 One solution to the problem is to set both the IC 746 and DX4WIN for CI V address 54H the same as the PW 1 But shouldn t each device have a distinct address 3 5 3 How do hook up a non lcom RF power amplifier Start by examining the diagram at the bottom of page 79 in your instruction manual but be careful it can mislead you into some expensive mistakes The ground and antenna connections are just as straightforward as they appear no problems there Do not hook the SEND output directly to your amplifier as shown You will need an external switching relay or circuit to avoid overloading the internal SEND relay Burning out the internal SEND relay is a common failure Not all amplifiers will have compatible ALC control signals The IC 746 ALC input runs from 0 to 4 Vdc W7DS designed a circuit to aid in automatic amplifier band switching that may be useful to you Check out the mods section of this FAQ for more details 3 5 4 Do I really need an external amplifier switching relay Most likely yes If you hook up a non Icom amplifier that does not have a solid state keying interface then you ll probably wan
58. and mics The DC power is fed directly from the rig through the mic cable If you are using a different electret microphone by sure it will operate with the 8 Vdc bias When using a dynamic microphone be sure you have a capacitor value not critical around 1 0 4 7 uf in the circuit to block the DC supply voltage Depending upon the microphone you may have to use a hefty amount of mic gain and possibly compression as well to make up for the lack of the handset pre amp You may even need to use an out board microphone preamp to get the signal high enough Finally the Icom microphone input is at a relatively high impendence 1 2K A matching transformer or preamp will yield the best results Most microphones operate at only 600 Page 37 of 113 2003 02 08 IC 746 FAQ ohms impendence and the impedance mismatch will exacerbate the signal level deficiencies Some microphones operate at much higher impedances as high as 100K and unmatched will suffer from distortion in addition to signal level problems Since you re already wiring up a new mic cable you might want to short pins 6 and 7 with the chassis ground to assure that they are at the same ground potential This often helps reduce RFI from coming in through the mic cable 3 3 3 Can I use a Heil microphone with the IC 746 Yes most Heil microphones work well with the IC 746 Bob does this himself As with any dynamic microphone be sure you have a DC blocking capacitor in the
59. ast resistance It is available through the usual retail channels It comes complete with both software and the necessary cabling OPC 662 Many people describe it as a thing of beauty Of course beauty only runs skin deep A description of the software can be found at http www icomamerica com amateur hf 746soft html To quote Icom s own support FAQ circa May 2001 Q Where can download the ICOM PC programming or cloning software A The ICOM programming software is not freeware and is not available for download on our Web site or anywhere else on the Internet It must be purchased either from an authorized Icom America dealer or direct from ICOM RT Systems also develops programming software for ICOM radios Ray the product manager at the 2001 Hamvention was very firm on this issue They take a dim view of the pirated copies available on the internet Page 62 of 113 2003 02 08 IC 746 FAQ Last word we know of January 2001 Icom had no plans to update fix enhance the RS 746 software RT Systems software OK so Icom refers us to RT Systems at http www rtsars com However as of May 2001 RT Systems does not have a 746 control program They told N8AVX in February 2001 that they had no plans to do so either Kingsmith Software Kingsmith Software is developing control software for the IC 746 RATS IC 746 but as of May 2001 it wasn t available yet More information is available at their WWW site at
60. at radio power feed e Ground the fuel pump and add RF suppression e Check the tachometer as a noise source e Add RF chokes to remote head cable not applicable to the IC 746 e Put snap on ferrite beads on the electronic ignition wiring bundle e Ground engine block to chassis This problem is not specific to the 746 all radios can be afflicted Covering this topic thoroughly is beyond the scope of this FAQ For more help information try the following http www arrl org tis info rfiignit html http www arrl org tis info pdf 001qex32 pdf http www k2bj com Pages Noise Intro htm http www qsl net ka6wke http www realhamradio com Ford F350 htm or join the mobile portable e mail list at http www qth net It turns out that someone DID write a book on this topic the ARRL RFI Book Chapter 16 is devoted to Automobiles Check out the description at http www arrl org catalog 6834 6 18 How do adjust or make the NB work better The NB is susceptible to both overload and cross modulation from strong nearby signals Often turning off the RF preamp or even turning on the attenuator will improve the performance Remember the IC 746 has plenty of gain to spare Page 77 of 113 2003 02 08 IC 746 FAQ The IC 746 Service Manual does have an adjustment procedure for the NB on page 5 10 Icom Tech Support provided W7GJ with a PDF copy of that page around Jun 25 2001 That PDF file is now available from several
61. atile it will allow 4 rigs to be controlled by a single RS 232 serial line It s also the most expensive option and requires external power If all you want to do is connect up a single rig then Icom s WWW site lists the OPC 662 remote PC control cable as the official part If you can find it then great Most people can t Instead many hams have successfully used the OPC 478 PC cloning cable It s less than half the cost of the CT 17 However it is very short 1 ft and will require a 1 8 inch stereo to mono plug adapter for use with the IC 746 When you buy the RS 746 remote control software from ICOM it comes with a single rig cable OPC 662 or OPC 4787 W2ENY sells a complete CT 17 clone and a single rig cable They re both more complete package than Icom s coming with cables and software resources on a CD ROM They re also cheaper You can find out more at http www geocities com w2eny civ http www geocities com w2eny icom_cable You could purchase the nearly universal rig interface the RigBlaster from the folks at West Mountain Radio It does a lot more than simply computer control and is adaptable to other manufacturers for a price http www westmountainradio com The Raymond Sarrio Company also make transceiver to computer interfaces http www sarrio com sarrio wlgee html There s really not that much circuitry in simple interface cables and many have homebrewed them for as little as 10 Supposedly the Nove
62. ator apologies if anyone has been missed AA6YQ Dave K3XT Sean ABOIO Marv K5HAL Cullen Langford AB2BK Len Davis K5UHF Ken S AB40J Adam Farson K6XX Bob W AC4JF David Waters K7RX Kevin ADIC Jim Reisert K7YVZ Jerry AD5CD David K7ZL Tom AD6ZU Roy K8AC Floyd Sense AH6LE Ken Arck K8CMA AK6R Bob Brehm K8UT Larry Gauthier K9EID Bob Heil DF4OR Ekki Plicht Germany K9HFX Scott Clayton KA4RQB Meade D EA7KY Julio Maleno Spain KB3CO Charlie KB9SSS Dana Hoggatt ERJC Noel W Ireland KB9ZLJ Chris Ryskoski KC2CJW GOHDB Martin Davies U K KC2EKI Tom G4FZN Chris U K KC5GGR Daniel Bowles G4YTL David U K KC5NSZ Rich G4YVM David U K KC8GLQ Mark Adams GW3WSU Colin Beynon U K KD6UU Howard Groveman GW4GTE Dave U K KD7EJC Charlie KE5DC Bill HK3BRO Francisco Carosio Columbia KF2TI Steve KF4TQV Frank KOBX Joe KF4YIO KOSD Stephen KG4HPM Bill K1XR Bruce KG4HPM Bill K1ZOK Ed Lambert KG6GLN Roy K2VI Tony C KI6QP Stuart R K3PGB Bill Abate KFOOH Bill Metzger Page 105 of 113 2003 02 08 IC 746 FAQ KJ6H Tod VE3CE Wayne M Canada KKSDR Matt E VE3EXT Jerry Beneteau Canada KT0OK Greg Brown VE3GWX Peter Canada KT3D Dennis F VE3
63. ave a link for it at the moment I ve been told that MARS Military Affiliated Radio Service must adhere to the same standards For both CAP and MARS some grandfathering did occur however that should have expired by now 8 17 How do I adjust the Noise Reduction NR The level of NR you want varies by mode and personal preference CW can generally tolerate more NR than SSB Most AM operators prefer little to none Fortunately setting the correct level is very intuitive Start with the minimum full counterclockwise setting 7 8 o clock Increase the level by turning clockwise the signal should sound better as you go After a while the signal will start to sound worse when that happens simply back off a bit So essentially you adjust back and forth until you home in onto the best setting Most people end up between 9 12 o clock for SSB and a little higher for CW As you eliminate noise you alter the signal In phone modes that s often interpreted as distortion At some point the perceived distortion becomes greater than the removed noise Page 96 of 113 2003 02 08 8 18 IC 746 FAQ How do program a non standard repeater offset Repeater offsets are just a special convenience case of general split operation If you need to set up such a repeater without changing your default normal offset then here s what you do as outlined on page 35 of the instruction manual 8 19 Go to VFO mode Depending upon t
64. below 13 5 V dc Check the actual voltage your rig is receiving You may need to adjust the voltage setting on your power supply If your rig isn t getting the voltage you think it should then check for voltage drops along the power cord as well as across joints fuses and connectors It s possible to lose as much as a half volt per connection Solder joints and use high quality connectors where possible 12 AWG wiring is the minimum but 10 AWG is better Some in line fuses have had their solder end caps oxidize thus interfering with current flow and dropping the voltage If you absolutely can t get your voltage up for example total battery power then you might consider adjusting the power settings for the RF PAs there are 4 of them However trying to run a full 100w output at the reduced voltage will most likely degrade the quality of your transmitted signal clipping IMD etc Most hams decide that 1 2db gains don t justify the crumby signal There is one more possible remedy for the low voltage problem You could get a DC DC voltage converter These are also called voltage boosters Such a device accepts 12Vdc in and yields 13 8Vdc output There s a price First they tend to only be 80 90 efficient so a 20A draw by the IC 746 can translate to a 25 29 amp draw by the converter Secondly commercial units like the Newmar 12 12 351 DC DC Converter can retail for more than 900 There is a more affordable ham designed and buil
65. btainable Shape factors of 2 0 or less are considered excellent This is one of those situations where a picture is worth a thousand words A good look at the spectral response curve of a typical filter will make these terms clearer Page 52 of 113 2003 02 08 IC 746 FAQ Inrad publishes basic performance curves of most of their filters on line An example of a typical curve is http www qth com INRAD graphs 116 gif ABA4OJ has a complete set of passband curves for Icom s filters on his WWW site at http www gqsl net ab4o0j icom filters filters html Several companies have good on line treatments describing basic filter characteristics complete with diagrams Corning Frequency Control has a very concise page styled in a glossary format at http www ofc com filters definitions html site not responding Jan 2002 Vectron International also has a nice on line treatment of filter characteristics at http www vectron com products xtal filter htm definition The folks at Piezo Technology Inc describe filter characteristics with attenuation curves http www piezotech com Technical_Information techindex htm 4 6 Why do filter bandwidth or shape factor matter Narrower bandwidths reject more noise and improve sensitivity Wider bandwidths provide better fidelity Narrower bandwidths also reduce the number of simultaneous signals the rig can hear This reduces the AGC pumping action caused by nearby signals pa
66. can eventually due to the long term electrical and thermal strain There s nothing to prevent you from frying the rig except luck There have been reports of output levels as high as 180w nearly 30 above the published ratings e Pushing the PA transistors closer to saturation moves them toward non linear operation thus increasing IMD and splatter Much of the extra power can end up as interference instead of in your signal Some IC 756 owners have found this out first hand that their rig uses the same transistors in its RF PA Distortion started at less than 110 watts e Increased heat dissipation may be a problem Nobody has any design spec data to tell how severe a thermal gradient the heatsink and fan was designed for Even if the PA transistors could handle the heat other components might not e Increased power supply current could cause unexpected problems What happens to your external power supply when you demand 30 A on transmit What about the 746 s internal voltage regulators e Increasing the power by 50 more than doubles the RF voltages within the internal ATU Thus making it more prone to arcing and burnout e Differing part tolerances can surprise you It s much easier to compensate for component variations when you stay well within their tolerances Thus some rigs may be more prone to the above problems than others Just because one ham s rig worked is no guarantee that your s will On the plus side you might be ab
67. cboncecossssesseastacsssessinioeenas 12 2 2 What are the IC 746 s features sscicisscascsccccsssesssscsscstoevesesvsssccndssauncccsnsescendsaceaasss 12 2 3 How does the IC 746 stand up to the ETE E EE 12 2 4 Where can I buy sell a used IC 746 soessoesssesssocssoossoossssesssecssoossoosssosssossssese 13 2 5 How much is a used IC 746 worth e ssesssecesooesoosssocsssesssocesoossoosssoesssoesssesesoeee 13 2 6 Is there a dedicated HF net for the IC 746 eessoesssesssesssocssoosssosssoesssesssoesesoeee 14 2 7 Are there electronic copies of 746 instruction manuals sssosssessseees 15 2 8 Are there electronic copies of the circuit schematics seesseossooesoosssoessseessese 15 2 9 Are there electronic copies of 746 service manuals scccsscscsscsscseseees 16 2 10 How do I fix the font substitution error in the PDF manual cccse0e 16 2 11 How does an I C 746s differ from an C 746 0 ccccccccsseccssssccccssescsssescesees 16 2 12 Whatis Ce IC 7400 iicccisscssvedercavxasssiceniganctewevencurnsteansnqpasenevstoscaneeemsonevanennnevens 17 2 13 What is the IC 746 PRO sississssssssesssisssosssssssosssss sssososssssss sssssssosesssss vssssssssso s 17 2 14 Where can I find info on other Icom rigs essseeesooesosesssesssosesoossoossoossssssssese 18 2 15 Where is info on the 706 718 756 765 735 sesesesosososososososososeoosooeoesosesesesoso 18 2 16 What articles have been written
68. ceived signal First make sure that RIT is turned OFF Then use one of the following two techniques e Adjust the frequency of the radio to where the pitch of the received CW signal is the same as your sidetone pitch Your accuracy may depend upon your ability to remember a perceived pitch Most people can get to within 10 Hz this way e Adjust the frequency of the radio until the pitch of the received CW signal is the same in CW mode as CW R mode By A B comparison you can reliably get to within 5Hz Either of these techniques will work very well There are other approaches but these two are the simplest most convenient and the most popular Yes it can be tough to zero beat a side tone against dits and dahs but it takes very little effort to get close enough to put your signal within the person s passband so that he will hear you even if he is using an extremely narrow filter Beware if you turn off break in operation so that you can hear your sidetone simultaneously with the other signal then you must remember to turn it back on again Otherwise you won t actually be transmitting you ll just be practicing your code Page 98 of 113 2003 02 08 IC 746 FAQ Instruction Manual Errata Know errors in the Instruction Manual by page number Page 2 Incorrect Page References 12 AF CONTROL references p 12 should be p 11 Page 6 External speaker and remote interface jacks are swapped Page 6 has the external speaker a
69. circuit to isolate the mic element from the DC supply voltage Heil s pre wired mic harnesses are perfect for this A notable exception is the HS 706 which as the sales literature clearly states ONLY works on the IC 706 series 3 3 4 How do l adjust the IC 746 for a Heil headset In theory the IC 746 has enough microphone gain to use an unaided Heil microphone Heil s May 2000 newsletter discusses this topic see http www heilsound com newslettermay00 htm In short you use moderate mic gain 50 75 12 3 o clock position along with moderate compression 8 10db 12 1 o clock position for the best results 3 3 5 Do I need a pre amp to use a Heil microphone While the above procedure works for most rigs it does not seem to work for everyone For the few that still have gain problems adding the Heil HMP microphone pre amp should work Some speculate that the differing mic gain requirements are due to different versions of the IC 746 or simply due to widely varying component tolerances Nobody has collected enough information yet to nail this issue down DO NOT use the HMP pre amp unless you re sure you need it Too much gain will distort your transmitted audio with all the usual detriments hard to copy splatter etc If you decide you need a pre amp but want to build it instead of buying it then check out Build a low cost Boost Microphone QST Aug 1989 along with the Icom specific mods available DC blocking ca
70. cites ieastacteastualastoeiviataty satu EE E dea ad ated 68 Contused Meter Readings iiss nsec dctescceeeiuedia ninpa Mins a a ean seagate nates 68 CW Break In Turned Olt a nrin acta a ee il Senter Gosia nahi eon ia 69 Internal adjustments set a little LOW se ock eis aac dessBeinnvaetoceaesyaases dat esnetissaseansessedeset 69 How low can the IC 746 supply Voltage be scccssccsssseccssecsscsescssseseesees 69 The backlight in my LCD has stopped working What s wrong 0 70 Is there some way to get the Icom 746 to generate DTMF tones s000 73 Why don t my band edge beeps match the US amateur bands 74 Can I transmit all the way out to the band edge beeps scscsseseseeeee 74 Can I reprogram the band edge beeps sssccscsscccsssesssssescsssessessssseeeees 74 Do we know anything about the band edge beeps csscccssscsssseseeeees 74 How I reset back to factory default settings cssccsssccccsscssssescssesceeeees 75 What birdies does the IC 746 have csccssscssscsssecssecssscssssssssesssssseseees 75 How do I adjust the LCD display ssessseesseossooesooessossssesssecssooesoossosssssesssosssoosso 76 The Noise Blanker doesn t seem to do any good What s wrong 00 76 How do I get rid of ignition noise eessseoesooesoossosesssesssocesoossoossosesssesssoosssoese 77 How do I adjust or make the NB work better
71. dged crystal filter either from Icom or Inrad In theory replacing the cheapo ceramic filter Murata CFJ455K with a superior crystal filter should improve the rig s performance Three obvious choices have been suggested e Inrad 109 crystal filter e Icom FL 44A crystal filter e Kokusai MF 455 11GZ mechanical filter One source of info claims that to do this mod with crystal filters requires changing 2 resistors R701 and R704 from 10K to 3 9K to change the impedance seen by the filter from 2K to about 1 2 1 5K Most do not bother N9IRD talks about this type of mod at http www gsl net icom n9ird html 7 3 Can increase my RF power output beyond 100w Yes but you probably shouldn t Technically this is more of an adjustment than a mod NI4L and others have outlined the alignment procedure for increasing the RF power output above 100 watts The basis for these procedures can be found on page 5 4 of the Service Manual The procedure can be found on line at http www mods dk http www qrz com download mods i k ic746pwr txt After examining the circuitry in the schematics and the specifications for the transistors involved http www qsl net kb9sss Parts 2SC2694 pdf Page 85 of 113 2003 02 08 IC 746 FAQ Most hams feel that raising the RF output power above 100w is a bad idea for a variety of reasons e You can exceed the power ratings on the output transistors Even if they don t blow out right away they
72. dra interface html He did all of this for the IC 756 PRO II but all of Icom s modern transceivers use the exact same ACC port interfacing so you should be all set now Page 49 of 113 2003 02 08 IC 746 FAQ 3 6 TNC 3 6 1 How do hook up a TNC to the IC 746 Check out the wiring diagrams available at http www packetradio com tnc to radio htm Page 50 of 113 2003 02 08 IC 746 FAQ 4 IF Filters 4 1 How many optional IF filters can install into the IC 746 There are two 2 slots for optional filters in the 9Mhz IF and one 1 slot for an optional filter in the 455Khz IF 4 2 What optional IF filters are available for the IC 746 Available filters for the 9Mhz IF include Filter IF Bandwidth SF Typical Use Inrad 121 9 Mhz 250 hz 2 2 CW narrow Icom FL 101 9 Mhz 250 hz 3 0 CW narrow Icom FL 232 9 Mhz 350 hz 2 8 CW RTTY narrow Inrad 111 9 Mhz 400 hz 2 3 CW RTTY narrow Icom FL 100 9 Mhz 500 hz 2 5 CW RTTY narrow Inrad 320 9 Mhz 1 800 hz 1 5 SSB Icom FL 223 9 Mhz 1 900 hz 1 9 SSB narrow Inrad 110 9 Mhz 2 100 hz 1 5 SSB Inrad 123 9 Mhz 2 800 hz 1 5 SSB wide Icom FL 103 9 Mhz 2 800 hz 1 8 SSB wide Inrad 306 455 Khz 125 hz 2 1 CW narrow might not fit Inrad 122 455 Khz 250 hz 1 8 CW narrow Icom FL 53A 455 Khz 250 hz 1 9 CW narrow Inrad 116 455 Khz 400 hz 1 7 CW Icom FL 52A 455 Khz 500 hz 2 0 CW RTTY narrow Inrad 322 455 Khz 1 800 hz 1 5 SSB narrow Icom FL 222 455 Khz 1 800 hz 1 7 SSB narrow Inrad 314 455 Khz
73. e Service Manual should help Icom UK told GW3WSU The transistor Q302 is available from stock but is a 2SB1201 it is only 47p carr and vat but unfortunately is below out lt A3 gt 10 minimum order charge You do not have to unsolder the pots remove the plastic front panel then undo the pot fixing nuts from the metal sub chassis and it should all just come away When you come to replace the transistor its best to remove the screening can this gives better access to the device After replacement would advise you to put a generous drop of heatsink compound across the transistor and spread it over to the metal of the screening can this will keep the transistor from getting too hot again in the future OZSACI used an overkill transistor from his junk box and had to cut a bit of the cooling fin to make it fit under the shield The original transistor is not very tall and can be left at an angle so no cutting is needed or wanted He says it s all fairly simple The only trouble is that the front section of the 746 has to be taken totally apart and getting it back together with Page 71 of 113 2003 02 08 IC 746 FAQ no dust behind the plastic screen is a pain Get yourself a small can of workshop compressed air or CO2 if you can VK4TZL Glenn reports The actual repair is relatively easy assuming that Q302 is the problem The whole repair took me one hour Removing the front panel from the radio by removing 4 screws and
74. e Twin PassBand Tuning TPBT to dynamically adjust your IF bandwidth first Properly used TPBT can give you nearly any bandwidth you want You may decide that you don t need any anything else There are over a thousand possible combinations of optional filters 1 539 at the last count Most of them will make sense i e be useful to someone somewhere As it is a matter of style and situation ultimately the choice will be up to you We ve broken up this issue into several questions each targeting a more specific issue or problem Short of writing a book it is the only hope of providing any useful answers At the end of this section we ve listed some popular combinations Don t use a filter combination just because it s popular Optional filters could total 500 or more Understand what and WHY you re buying to make sure you get your money s worth 4 4 What is an IF filter s bandwidth 4 5 What is an IF filter s shape factor Also called passband a filter s bandwidth is a measure of how wide a signal will pass thru the filter For IF filters this is typically measured as the span between the filter s 6db points Some folks measure bandwidth at the 3db points Pay careful attention to the specifications when comparing filters Shape factor tries to represent steepness of the filter s attenuation curve Typically defined as the ratio of the 60db passband to the 6db passband bandwidth The perfect shape factor of 1 0 is uno
75. e keyer control The software configuration implications are left as a puzzle for the reader When building the G3VGR version AD6ZU makes the following observations found that the G3VGR interface to be quite easy to build inside the DB 9 shell The parts are cheap and it s quite tolerant to using components not listed on the schematics used 2N3904 s instead of 2N2222 s because they were what had also used 5 1K resistors instead of 4 7K and had no problems with the interface I ve built about a half dozen so far and the suggestions have for this interface are Start with the shortest connections the shorting of the pins Imagine working from the connector toward the back of the shell This makes for a much neater layout than randomly building the circuit ugly style You can practice by building your first interface that way since the parts are so cheap it s easy to build another one Page 60 of 113 2003 02 08 IC 746 FAQ Physically stack the two transistors atop each other with the two emitters twisted together This helps to keep the volume down A little heat shrink tubing may help here and there but use it very sparingly it adds volume and a smart layout really doesn t require any Use a highlighter to trace out the connections you ve made It s easy to get mixed up as to which connection you ve made and which ones you haven t Be sure to strain relief the cable in the shell An inadvertent tug on the cable c
76. e scratches you could try a product call Everclear Apply witha cotton ball then remove with a clean cotton ball There s more info on this product at http www onecybersquare com shopping everclear how_to_repair_clear_surfaces htm These are only suggestions from people who have had to cope with this problem YMMV 6 22 What can I do about sticky switches KF4YIO cleaned his switches by spraying a LITTLE contact cleaner in the spaces between the switches and the faceplate and that cleared up the problem Make sure the spray cleaner will not damage the plastic knobs or face Page 80 of 113 2003 02 08 IC 746 FAQ 6 23 Why does the S meter seem low on 2m FM While this is apparently common on many modern multimode rigs we do not know precisely why The S meter sensitivities published in the QST product review did not show a problem on 2m 6m is a different story but nobody seems to complain about 6m readings Likewise the measured receiver sensitivities do not reveal any problems Some dealers blame all this on the wide band receiver technology but again that doesn t really answer the question Turning on the preamp will increase the reading 6 24 Why is my tuning shaft knob loose and sloppy If the factory did not tighten the nut that holds the main tuning unit then over time movement may cause the friction screw to crack the faceplate This is a hard one to get at 6 25 Why is my audio cu
77. e shield covering the left rear compartment on the RF unit J1 is located near the rear panel right next to the Key jack and just behind a small relay on the board Using the Icom PC connector pair and two short lengths of miniature coax construct two pigtail cable assemblies with a RCA female jack on one end and a male and female PC connector respectively on the other If you are really careful you can use RG 174 miniature coax but if possible try to find some RG 188 or similar coax with Teflon Page 83 of 113 2003 02 08 IC 746 FAQ dielectric This will make it a lot easier to construct the input and output cables without melting insulation The male PC connector is designed for crimp termination but it can be soldered as well just stripped the center conductor of the coax and carefully soldered it into the center pin made a small pigtail with the braid and tacked it to the top of the shell Be careful It s really easy to apply too much heat and displace the center pin Once the assembly is complete check it with an ohmmeter to be sure it s not shorted The female PC connector is really designed for PC mounting so it s a bit tricky to install the coax took a small piece of 26 bus wire and wrapped it around the ground pins and tack soldered the shield to this wire then encased the junction in heat shrink tubing to immobilize the connection Although it s a little close the ends of the completed assemblies with the PC c
78. eatly appreciated However general discussion debate over the answers is best done in a more public forum like one of those mentioned above 1 4 What are the future plans for the FAQ Starting in February 2003 this FAQ went from a text ASCII format to Adobe Acrobat PDF format This is facilitating the inclusion of charts and diagrams along with bookmarks and hyperlinks That process will continue To view or print the document you will need a copy of the Acrobat Reader available for free from http www adobe com products acrobat readstep2 html Most of the power supply information should be separated out into a separate FAQ that is applicable to all rigs This fits in better with the new ICOM Resource pages at http www qsl net icom Page 10 of 113 2003 02 08 1 5 IC 746 FAQ What questions still need to be answered There are plenty of topics that still need or deserve to be covered Here are some topics and details we d like information on in no particular order Levels and impedances of all audio connections mic phones acc etc We still do not have enough reliable reports to confirm which birdies if any actually exist How does one go about hooking the 746 up for PSK TNC and CI V operations at the same time CW Zero Beat confusion as well as BFO and reverse operation More information is needed on the front panel power switch and its interaction with the extra pins on the T connector in t
79. eca co e Kadani Kaie saie kadada dadadada adadni ada aia aaea 109 Page 8 of 113 2003 02 08 1 1 IC 746 FAQ ADMINISTRIVIA What is an FAQ 1 2 Where can I get a copy 1 3 Where do I send feedback Welcome to the IC 746 FAQ Short Answer FAQ stands for Frequently Asked Questions It tries to cover common questions problems and issues associated with Icom s IC 746 HF VHF amateur radio transceiver The master copy is kept at http groups yahoo com group IC746 files IC746 faq pdf Mirrored copies after a short delay appear at http www qsl net kb9sss IC 746 1C746 faq pdf http www skysdaughter com icom746 faq pdf You do not need a Yahoo email account to access the master copy however you will need a logon account Yes that is a subtle but hopefully minor distinction Not everyone is willing to have a login account at Yahoo even if it is free which is one of several reasons for maintaining the mirror sites Also we post the FAQ monthly to news rec radio amateur equipment usually sometime between the Ist and the 10th You can post questions comments about the FAQ to the above newsgroup Long Answer The format of this FAQ should become apparent right from the start Questions are grouped into related sections and subsections roughly in the form of an outline When possible practical there will be both a short and long answer The short answers will try to be brief and to the point typically
80. eeaeeenseeneeeaees 84 PoorMans TOXO geeis a E E E RE waded doneeatas O RRA 85 Upgrading Stock Ceramic IF Filter to a Crystal Filter 0 0 eeceesseeeteeeteeeees 85 7 3 Can I increase my RF power output beyond 100W u scccssscccseesceeeesees 85 7 4 I m brave what untested mods are there cccccccccscsssseccsecesecesesesecesers 86 Replacing PIN Diodes in the Demodulator nsssnenneesensseeseeseesseesseseesseessessesseesse 86 Removing the BCB Attenuator cccccccccsccsssecsecesecseeecescecseceseeseneesseecseeceeeeaees 87 7 5 What external mods are there for the C 746 ssscsssssssesssesssessssesees 87 Remote Direct Frequency Entry Keypad cceccceccessceesseeeeceseceeeeeeseeeseenseenees 87 Cordless Headset Mictophoniess c2 ccsaciiayssicalbavieassanstaniencauancasiatananteatineds 87 Automatic Antenna Amplifier Selection by Band cc ceceeceeeeeteeneereeeeeeeeeenees 87 2m TX RX SEQUENCE cranes eeii ia sauce EE E Ea 88 Eternal T ner Pulser fsijess tin telacteeic anuna ar a a a wag aa 88 Unmuffling Icom Hand Mites 5 ss sseccascases Sateen sient eeteien teeth sete 89 8 IES ssa A A cc essence ceezediat rcv A eu edakstdvedensceewasnaas 90 8 1 Are there different versions of the C 7462 csscssscssssssssesssscsssssssssscssnees 90 8 2 Can I operate 2m on reduced power ssesssesssocssocssooesoossssessseessoossoossoossssesssese 90 8 3 Where can I find plugs for the ACC co
81. either R1111 or R1291 which are identified as AHY103 relays in both the parts list and the schematics We believe the part is supposed to be an OMR 109F Page 102 of 113 2003 02 08 IC 746 FAQ Glossary Here are short expansions of some of the more common acronyms you ll encounter when reading about the IC 746 This document is not a dictionary these are not definitions A more comprehensive and detailed listing of terms can be found at http www qrz com i hamspeak html ACC ACCessory connector AF Audio Frequency AFSK Audio Frequency Shift Keying AGC Automatic Gain Control ALC Automatic Level Control AM Amplitude Modulation ANF Automatic Notch Filter ANL Automatic Noise Limiter ANT ANTenna APF Audio Peak Filter ARRL Amateur Radio Relay League ATT ATTenuator ATU Antenna Tuning Unit BCB BroadCast Band BFO Beat Frequency Oscilator CAP Civil Air Patrol COMP COMPression DSP Digital Signal Processing DTMF Dual Tone Multi Frequncy touch tone FAQ Frequently Asked Questions FM Frequency Modulation FSK Frequency Shift Keying IF Intermediate Frequency IMD _ Inter Modulation Distortion LCD Liquid Crystal Display LSB Lower Side Band MARS Military Affiliated Radio Service MIC MlICrophone NB Noise Blanker NR Noise Reduction PA Power Amplifier PBT Pass Band Tuning PCB Printed Circuit Board pig Pig is to rig as lemon is to car PLL Phase Locked Loop PTT Push To Talk QRP low power operation Page 10
82. either the Icom FL 44A or the Inrad 109 The superior characteristics of these filters over the stock ceramic filter probably improve every one of the important receiver specs However the filter is unpopular Most hams simply have trouble justifying 100 200 for a filter they already have the stock filter has the same bandwidth Given that caveat here are some popular filter combinations you might want to ponder None Single 500hz wide CW filter in either IF Dual 500hz wide CW filters one in each IF Single narrow SSB filter in either IF Dual narrow SSB filters one in either IF One wide CW and one narrow SSB filter at 9Mhz IF Icom vs Inrad 455Khz vs 9Mhz Mostly a matter of preference read above and probably not as important as you think otherwise you need to read the more detailed material above Page 58 of 113 2003 02 08 5 5 1 IC 746 FAQ Computer Control How do I wire the IC 746 up for computer control 5 2 What cables do need 5 3 What are CT 17 OPC 478 OPC 662 all about The IC 746 is computer controllable through a serial interface but it is not RS 232 This is both good and bad Bad because you can t just plug it straight into your computer wrong voltages etc Good because you can control four separate rigs with the same serial line Therefore to connect the IC 746 to a computer requires some interfacing Icom made three the CT 17 OPC 478 and OPC 662 The CT 17 is the full boat Vers
83. er You do have to go to the key set menu and tell it you will be using paddles See Page 23 and page 27 in the operation manual While in CW mode press KEY F4 then press SET F5 Press the down arrow F2 until you reach the sixth menu KEYER TYPE Use the Main tuning knob to set the type of keyer to Elec Key or bug Key to use the bug without electronic keyer ELECTRONIC KEYER Accepts a paddle to activate the internal electronic keyer 3 4 4 Can use the internal and external keyers at the same time Sure you can have an iambic keyer plugged into the front and a straight or external electronic keyer plugged into the back You can then use either interchangeably We don t yet know of anyone brave enough let alone capable to actually use both keys SIMULTANEOUSLY Would such an person be a two fisted operator 8 Page 41 of 113 2003 02 08 IC 746 FAQ 3 5 Amplifiers 3 5 1 How do hook up an Icom IC PW1 RF power amplifier The electrical connections are easy just follow the diagram at the top of page 79 in your instruction manual Then carefully read the instructions that came with the IC PW1 because they can be confusing Icom has instructions for this on their WWW site at http www icomamerica com support documents pw1 746 html They state 1 Make sure the CT 17 is powered up Connect the CT 17 output 1 to IC 746 and output 2 to IC PW1 2 Power up the IC 746 and set up the CI V communication
84. er reviews on Inrad crystal filters at http www eham net reviews detail 1499 4 11 Which IF should I put an optional filter into Realistically the performance differences between using filters in the 9Mhz IF vs the 455Khz IF are fairly small and will probably go unnoticed in normal operation Most people make this decision based upon slot availability and filter cost 4 12 What s different between IF filters for 9Mhz vs 455Khz 455Khz IF filters tend to have superior performance characteristics while 9Mhz IF filters tend to be less expensive There are other differences filter blow by ultimate rejection earlier roofing etc but usually it all comes down to cost When money is no object you ll want to use one of each On a tight budget you ll do fine with whatever you can afford 4 13 What are the 9Mhz IF filters best for When dealing with interference from nearby signals the sooner you reject the unwanted signals from your RF chain the better So a single narrow IF filter in a 9Mhz slot will sometimes outperform a single filter in a 455Khz slot 4 14 What are the 455Khz IF filters best for 455KHz filters tend to have superior shape factors which seem to do a better job of eliminating background noise and allow tighter adjacent channel rejection So a single narrow IF filter in the 455KHz slot will sometimes outperform a single filter in a 9MHz slot 4 15 How do get the best results from TPBT TPBT works best
85. er transmit fidelity or even broadcast quality sound then you ll want a full range microphone possibly with a dynamic element Icom s own SM 20 gets good reviews for this application as does Heil Goldline microphones Other microphones will also work these just happen to be the most popular Many operators have found that the inexpensive studio microphones from Radio Shack work astonishingly well Yielding 90 of the performance at 10 of the price makes this a viable budget conscious choice It also shows just how poor the stock mic is If you re after more punch for DXing or contesting then you ll want to look into one of the Heil DX style microphones They re frequency responses have been tailored to accentuate the portions of the voice spectrum that most contribute to understandability Their great performance have made them very popular For those of you who want it all Heil even makes a microphone that switches both ways literally It has two pick up elements in the same mic so you can change between ragchewing and DXing punch at the flick of a switch Who says you can t have your cake and eat it too 3 3 2 Can I hook up a different microphone directly to the IC 746 Yes but only if properly wired There is more to wiring up an external microphone than just the differing pin outs You will also have to deal with DC bias signal level and impendence Icom uses electret elements and incorporate preamps right into their h
86. ere is a checklist of several possible actions not in any particular order Using TCN set the SSB TX Tone control to H SSB TX Tone affects all voice modes Turn off COMP compression Use a higher quality microphone Use microphone shock mountings and pop filters Use external microphone equalization Feed transmission audio directly via the ACC port bypassing the microphone preamp may not help the PRO as much as the CLASSIC e Make sure supply voltage is 13 5 V or higher e Lower RF output e Adjust by monitoring signal on a second receiver 8 13 Can the IC 746 transmit at less than 5 watts Yes with the help of some external circuitry The IC 746 isn t really designed for QRP operation the 2 amp draw on receive should prove that The front panel control will only get you down to about 4 5 watts However you can apply a voltage to the external ALC input to get even lower 0 to 4Vdc input yields 0 to 100 Watts output One ham even uses a simple voltage divider pot arrangement powered by 2 AA batteries KS5UHF warns that there can be a minute moment of higher power output before the external ALC level kicks in Not normally a problem unless you re driving input sensitive equipment like transverters 8 14 How do I turn on both HF pre amps at the same time You can t Nor would you really want to HF preamp 1 is transistor based and yields about 10db gain for the 1 8 54 Mhz range 160m to 6m bands HF preamp 2 is IC
87. ernal equipment amplifiers antenna switches etc based upon what RF band the transceiver is currently switched to There are two basic approaches for this One approach attempts to interpret the data transmitted by the CI V interface Icom s amplifiers are a good example Others attempt to decode the band voltage available from the ACC port Most projects use that approach Page 87 of 113 2003 02 08 IC 746 FAQ WD7S wrote an article for the May 2000 QST entitled Automatic Amplifier Selection for the ICOM IC 746 IC 736 and IC 706MKII Transceivers Hewitt Paul WD7S May 2000 QST p 33 K6XX has similar circuitry described on his WWW site at http www k6xx com radio icbsciv html Another copy is at http krasnodar online ru hamradio w7ds htm EI7BA has some related projects on his site at http www 1iol ie bravo remote htm There are also commercial solutions at http www rfapps com ibs 1 htm http www qth com topten bdecoder htm http users skynet be ON4A OI banddecoder shtml Here is a CI V based approach http www microham com product1 htm 2m TX RX Sequencer G3SEK outlines a complete TX RX sequencer for handling more complicated transceiver transverter amplifier hookups http www ifwtech com g3sek dx book sequencer External Tuner Pulser This is covered in the Antenna Section as well You can make the IC 746 think that there is an ATU out there with a dummy plug like that available fr
88. g All of the IC 746 filter settings are on the basis of Icom part numbers This is supposed to make things easier for new operators Just tell the rig you ve installed the Icom crystal that most closely matches the one you re actually using Lying to the rig does have a side effect The 746 cannot actually shift the IF filters passbands Instead the 746 shifts the local oscillator frequencies of the 2nd and 3rd IF stages to shift the signal back or forth aligning the edge of the desired signal with the computed edge of the filter s passband Small lies generate small effects like when you tell the rig that a 2 1Khz wide filter is actually 1 9Khz wide yielding a 100hz offset in the control Larger lies generate larger effects like when you tell the rig that a 400hz filter is actually 2 4 Khz wide yielding a 1 000hz offset in the TPBT control 4 18 How do I use a CW filter in SSB mode to receive PSK31 Icom took their ease of use one step further and programmed the rig to prevent the use of a CW filter while in SSB mode probably to prevent what they considered to be a foolish user error They didn t know about PSK31 at that time So again you lie to the rig during setup telling it that the crystal is wider so that the rig will allow you to select it for SSB use Page 56 of 113 2003 02 08 IC 746 FAQ 4 19 Why is there only one optional 455Khz IF filter slot Nobody knows for sure but the most popular speculation is that it m
89. g the LCD brightness to HIGH may reduce the failure rate Long Answer Unfortunately this has become a problem for many 746 rigs as evidenced by the data collected at http groups yahoo com group IC746 database method reportRows amp tbl 2 It s not the actual lamp itself but one of the driver transistors The lamp is fluorescent and will probably never wear out Even if it did the lamp isn t available as a separate part it s part of an assembly you need to get from Icom Background into problem There is a DC AC converter driving the lamp Check the S Logic board for transistors Q301 Q302 Q303 and Q304 Q302 is usually the culprit as it is the voltage current regulator for the dimmer function If you have a DC voltage on the collector which is Page 70 of 113 2003 02 08 IC 746 FAQ variable by the dimmer function on the radio then this transistor is probably OK Q303 and Q304 are the next most likely candidates These 2 transistors are in push pull configuration to drive the X former base is 180deg phase shift by the X former Refer to pages 6 1 9 1 10 1 and 11 2 in the Service Manual for more details Several folks at http groups yahoo com group IC746 database method reportRows amp tbl 2 have successfully performed these repairs themselves OZSACTI feels that the way the Q302 transistor is mounted is a design flaw Icom used the cooling fin of the transistor as a soldering point thus if it gets too hot
90. ger at the 2001 Hamvention was very firm on this Hard copies are available through any Icom retailer as well as through the W7FG Vintage Manual WWW site at http www w7fg com 2 10 How do fix the font substitution error in the PDF manual When trying to read the PDF version of a 746 Instruction Manual with the Adobe Acrobat Reader some people encounter the following three dialogs on page 10 of the document PDF page 12 A font required for font substitution is missing An error has occurred that may be fixed by installing the latest version of the Japanese Language Support package Unable to find or create font Ryumin Light Identity H Some characters may not display or print correctly The error is not fatal There are about dozen places in the manual where text in diagrams will show up as a series of dots You can get rid of the error by downloading the appropriate Asian font package directly from Adobe s support pages As of November 2001 the appropriate link was http www adobe com support techdocs 2a156 htm 2 11 How does an C 746s differ from an IC 746 Japan has a 3rd Class license that is power limited sort of like the defunct US Novice class The IC 746s is identical to the IC 746 except that it caters to this limited operating class It s output power is limited to 10w on HF and 20w on VHF Nobody has yet reported a mod for this rig to bring its power up Page 16 of 113 2003 02 08 IC 746 F
91. gh correlated reports yet to confirm these as birdies More information and reports are needed 10 503 30 002 0 io i 13 991 0 50 001 1 981 0 13 999 0 50 006 3 608 18 078 50 533 0 18 433 144 400 7 008 21 150 9 468 28 001 10 106 Page 75 of 113 2003 02 08 IC 746 FAQ 6 15 How do I adjust the LCD display Page 66 of the Instruction Manual describes how to change both the LCD contrast and the LCD backlight Push MENU to select M2 Push button to select LCD Push buttons to select lighting or contrast Turn the tuning knob to adjust value 6 16 The Noise Blanker doesn t seem to do any good What s wrong Probably nothing Possibly your expectations Noise blankers are placed in the IF signal path and designed to gate mute attenuate out impulse noise Impulse noise is characterized by very sharp pulses steep rise time and short duration Such noise is typically a result of ignition spikes and certain types of power line noise A good clue comes from the 746 service manual The NB adjustment procedure uses square wave pulses 30 mv high and msec long Therefore a NB is not a panacea Unlike an ANL or DSP a NB will have little or no effect upon static crashes and or white noise Noise generated by power supplies fluorescent lights and power inverters are generally unaffected The NB works best when impulse noise is strong and the signal is weak like mobile in a vehicle Most hams report that the 746 s
92. hat is an IF filter s bandwidth seoesooessoesssesssecssoossocossoossoossssesssosssoosso 52 What is an IF filter s shape factor seesseoessoessosssseessecesoossoosssosssoesssosssooseo 52 Why do filter bandwidth or shape factor matter sccsscsssessseses 53 What is considered to be a narrow filter scccscsscssscsssssesscssssssssssseoeses 53 What are narrow IF filters used for scssccssccssccssscssssscsssssssossssssssssseness 53 Can an IF filter be too Marrow ssccsssssesstesccssncsessecscssecoonsacssorcdesssenecstadossuscecenessons 54 What s the difference between IF filters from Inrad vs Icom s00000 54 Which IF should I put an optional filter into ccssccssessssessesssesssssseees 55 What s different between IF filters for 9Mhz vs 455Kh2 cscscsseseeeeeee 55 What are the 9Mhz IF filters best for scssscsssecssscsssscsscssesssssssssescseesees 55 What are the 455Khz IF filters best for ssccssccsssccssscsssesssesssesssssscessees 55 How do I get the best results from TPBT ccsssccsssscsssscsccssesceesesceseees 55 How do I configure the IC 746 to use an optional filter sscssscssseesees 56 How do I configure the IC 746 to use a non com filter sscsscsssessees 56 How do I use a CW filter in SSB mode to receive PSK31 ssccsssesseeseees 56 Why is there only one optional 455Khz IF fi
93. have the 8 pin DINs in stock 274 026 They are compatible after you remove the center pin Page 90 of 113 2003 02 08 IC 746 FAQ 8 4 What are the pin outs on the ACC 1 connector Page 72 of the Instruction Manual has the full scoop Here is a brief description RTTY High gt 24Vdc Low lt 0 8 Vdc Current lt 2ma GND HSEND Input Output for HF 6m When grounded transmits Goes to ground when transmitting Ground level 0 5 to 0 8 V dc Output current lt 20 ma Input current lt 200 ma MOD Audio input direct to modulator Bypasses microphone preamp and VOX 100 mV rms at 10 000 ohms AF Audio output fixed level Also monitor output when transmitting 100 300 mV rms at 4 700 ohms SQLS Goes to ground when squelch opens Current 0 1 ma 13 8 V Unregulated connection to main supply voltage Max Current 1 amp ALC Automatic Level Control 0 to 4 V dc yields 0 to 100 w RF output Page 91 of 113 2003 02 08 8 5 IC 746 FAQ What are the pin outs on the ACC 2 connector Page 72 of the Instruction Manual has the full scoop Here is a brief description 8V lt 10 ma at 8 V dc 0 3 V GND Connected directly to pin 2 on ACC 1 HSEND Connected directly to pin 3 on ACC 1 AJOIN gt BAND VP Ey LF Band output voltage Varies from 0 to 8 V dc 160m 80m 40m 30m 20m 17m 15m 2 2V 12m 10m 1 9V 6m 2m
94. he back More service and repair information Better explanation of band stacking registers Operating tips Instructions on how to use internal ATU Better explanation of COMP gain FM etc Compare contrast the 746 vs 746PRO Does the 746 exhibit a full power spike at beginning of TX We welcome and encourage submissions 1 6 What does this abbreviation or TLA mean Hams use a lot of abbreviations and TLAs Three Letter Acronyms Toward the end of this document is a small glossary to some of the abbreviations we use in the FAQ Page 11 of 113 2003 02 08 IC 746 FAQ 2 GENERAL INFO 2 1 Should I buy an IC 746 Yes Try it you ll like it This FAQ is maintained by happy loyal and devoted IC 746 owners What do you really think we re going to say One thing nearly everyone both loyalists and detractors agrees upon is that you should make every effort to try out a rig before purchasing it 2 2 What are the IC 746 s features For features check out the IC 746 specifications from brochures available at your local amateur radio equipment store on line documents at various vendor sites or directly from Icom s WWW site at http www icomamerica com On line copies of the IC 746 sales brochure are available at http www qsl net kb9sss IC 746 IC 746 Brochure pdf http groups yahoo com group IC746 files IC 746 Brochure pdf Of particular interest might be the on line copy of the instruction manual M
95. he frequencies involved you may have to turn off AUTO REPEATER temoprarily Set VFO A to RX frequency plus RX PL tone tone squelch if needed or desired Set VFO B to TX frequency plus TX PL tone Switch back to VFO A Press the SPLIT button so indicator light comes on Store into selected memory slot as usual Turn AUTO REPEATER back on if desired How do turn on repeater PL tones There are two different tones you might need In the USA PL tones are used while in Europe a 1750Hz tone is used You access them both the same way Page 34 of the instruction manual covers the procedure which we summarize here With the frequency set to somewhere in the 2m band with M1 displayed press the menu button to get M1 displayed if M2 is displayed You ll see TON above the F3 button Press and hold F3 you ll see Rptr Tone come on the display Release F3 Spin the tuning dial to get the tone you want Press the menu button to get back to seeing M1 displayed Watching the display press F3 briefly Each time you press F3 that way you will see the letter T come on the screen or off the screen about 3 4 of the way down from the top above the F4 button When the letter T is on the screen sub audible tone transmission will occur when you key the mike Page 97 of 113 2003 02 08 IC 746 FAQ 8 20 How do zero beat a CW signal Zero beating ensures that your CW signal is being sent at exactly the same frequency as the re
96. ill only handle a miniscule load An external switching circuit will be required The SEND jack RCA phono connector on the back of the rig is relay operated and is output only However the HSEND and VSEND signals that are available from ACC1 pin 3 ACC2 pin 3 ACC2 pin6 and MIC pin 5 are all bi directional These leads go to ground through a transistor when the rig transmits Actively grounding these leads will put the radio in the transmit mode You ll almost certainly need a solid state isolation circuit of some sort for this to work correctly 3 5 9 How do I build my own SEND relay isolation circuit relay Your design will be dominated by several basic considerations the voltage load polarity requirements of your amplifier your choice of SEND jack keying or ACC port keying and your choice of relay or solid state switching The send relay in the IC 746 and others closes 10 to 11 milliseconds before the start of the RF and opens about 7 milliseconds after the end of the RF If you use a relay between the rig and the amp it had BETTER BE FAST The relay in the amp needs to be closed before the start of the RF This means the amp relay AND your intermediate relay together must be faster than 10 msec In general solid state systems tend to switch faster than mechanical systems However the relay based systems tend to be easier to design build and are more versatile The line used in the ACC port for this is a bi directional signal i
97. in the 13 volts otherwise they will be gone before you notice After you properly adjust of the bias current you can remove the safety resistor The RF power amplifier transistors may have failed In the IC 746 there are separate PA s for HF 6m and 2m Each PA uses a matched pair of 2SC2694 s If you ve lost power from one but not the other then this is a strong possibility As with the driver transistors have the service manual on hand and be prepared to readjust realign everything afterwards Blown Output Detector Diodes Blown diodes in the SWR detector can fool the power fold back circuitry into cutting back power unnecessarily The blown diodes will be shorted This can easily happen by playing around with an external antenna tuner in conjunction with the internal ATU Your ALC circuit may have failed A failure within the ALC circuitry can cause a drop off in power SWR Foldback The IC 746 is very sensitive to any sort of SWR mismatch Even a mild mismatch of 1 3 1 can have a significant impact In fact a few hams have even encountered this when feeding amplifiers Turning on the internal ATU is a simple fix Confused Meter Readings When checking RF power output you should always use CW It is normal for the output meter to read considerably lower during voice transmissions than during CW transmissions The average male voice has a peak to average power ratio of about 14 dB which means that an indicated average outpu
98. itching Kenwood PS 52 20 22A linear Power supplies to avoid via testimonial Astron RS 20 overloads too easily Kenwood PS 30 overloads too easily Diamnond GZV 4000 RF hash on 40 20m Icom PS 85 RF hash Long Answer This question typically arises for one of two reasons Either someone wants to buy a new power supply or they have an existing power supply that they want to use In both cases the issues are load capacity size weight electrical noise mechanical noise cost features and appearance Buying a new supply gives you a lot of options there are plenty of great supplies out there With an existing supply you have no control over these factors you re simply looking for a fit You ll want to consider the following factors Reviews QST tested and reviewed many supplies in January and September 2000 You ll find the results informative ARRL members can access those and other reviews on line at http www arrl org members only prodrev pdf pr0001 pdf Page 23 of 113 2003 02 08 IC 746 FAQ http www arrl org members only prodrev pdf pr0009 pdf Transportability The larger the capacity the larger and heavier the supply If size and weight are critical for you consider a switching supply as they are usually less than half the size of a linear supply Electrical Noise All supplies generate some electrical noise Typically the noise from linear supplies will be in the form of AC hum while from sw
99. itching supplies the noise will be RF hash Communications grade power supplies of either type are designed to minimize the noise and generally cause no problem i e this is not a good place to cut corners Computer power supplies that are pressed into radio service are particularly bad when it comes to electrical noise Usually the harder you push a supply the heavier the load the worse the noise will become Mechanical Noise Many supplies have cooling fans Sometimes the fans are loud enough to be a noise problem themselves Fan noise is variable from supply to supply even within the same manufacturer and model Likewise hearing tolerance varies from operator to operator Thus it s hard to tell in advance if a specific supply will have a problem Time may yet tell We do know that fans are driven by load The closer you operate to a supply s capacity the more the fan runs Also some of the transformers used in linear supplies will generate an audible hum The transformer itself vibrates with the AC supply Mass seems to help here Usually but not always the heavier the transformer is the less the hum Its pretty easy to put a noisy power supply under a table behind a cabinet or elsewhere to cut down on the noise level Just be careful to allow proper airflow for cooling Features Most of us consider current limiting over voltage protection and high temperature shutdown to be mandatory in a new supply Fuses or
100. l sensitivity to use Again we don t know of anyone willing to admit to performing any of these modifications If you perform one of these or some other esoteric mod then we d love for you to share your results with the rest of us 7 5 What external mods are there for the IC 746 These modifications are not made on the IC 746 internal circuitry but are external interfaces of one sort or another Remote Direct Frequency Entry Keypad W2ES wrote an article for the Dec 99 QST entitled A Direct Frequency Entry Keypad for ICOM Transceivers The Millennium QSYer is based upon that design and available from http www john hansen net keypad htm Cordless Headset Microphone Some hams have come up with a clever way to add a cordless headset to their rig Basically you find a cordless phone with a soundcard interface on it something designed to work with your PC as an Internet phone The IBM3330 900Mhz phone is a popular choice You hook up the phone to the transceiver like you would a PC and then use VOX to control TX RX Some have had great success W8 WWYV provides all the details at http www seed solutions com gregordy Amateur Radio Experimentation CLessPhone htm Instead of a cordless phone you could try using one of the cordless microphone headsets they sell for use with computers Automatic Antenna Amplifier Selection by Band These are also refered to as automatic band decoders Its the art of contolling ext
101. lation but no confirmation that an HM 95 microphone might also work with a suitably wired adapter If you succeed with such an experiment please let us know KC2CJW has successfully adapted an Alinco EMS 11 microphone for use on the IC 746 You ll need two cable mount 8 pin microphone connectors one female one male a couple of inches maybe a foot of decent multi conductor cable a 470 ohm resistor and some soldering skills Paul can provide pin outs upon request Another option is a portable tone dialer such as one that you could get at any Radio Shack Just send the tone sequence right through the microphone Not all such devices give access to the A D tones but those tones don t get used much anyway Some have suggested wiring a DTMF pad into a microphone cable much like what you would do for a TNC However as yet nobody has shared any success stories Far Circuits at Page 73 of 113 2003 02 08 IC 746 FAQ http www farcircuits net dtmfl htm have some circuits that might be adaptable Perhaps someone could base a design upon the NS TP 5089 http alds stts edu datasheet DTMF NS TP5089 pdf http www boondog com 5Ctutorials 5Cdtmf 5Cdtmf htm Another approach is to let your nearby PC generate the tones Those with PSK31 or equivalent audio interfaces will find this relatively easy to do Here are a few of the many DTMF programs for the PC http www silverstones com DTMFdial html http groups yahoo co
102. le to increase your RF output by as much as 1 2 dB That s a lot of potential problems for a meager gain Most hams don t feel that it is worth it If you really need more than 100w out then you should probably consider an amplifier 7 4 I m brave what untested mods are there While several other mods have been discussed to date we don t know of anyone brave enough to try them Replacing PIN Diodes in the Demodulator Likewise it is speculated that the IC 746 has cheapo PIN diodes in the detector circuit Again in theory replacing these with higher quality components closely matched would improve performance in particular the 3rd order intercept point This mod even helps the famous IC 781 which is where the idea came from The IC 746 PRO is not eligible for this experiment It uses it s DSP for modulation and demodulation Page 86 of 113 2003 02 08 IC 746 FAQ Removing the BCB Attenuator A few folks have noticed that the IC 746 is less sensitive below 1 6Mhz This appears to be due to an additional attenuator being switched in to protect the first RF amplifier from overload by comercial broadcast transmitters Some theorize that removing the extra attenuator by simply bypassing it with a jumper would improve the sensitivity This involves R11 R14 on the RF board see p 11 5 of the Service Manual for the schematics Others point out that the atmospheric noise level on that band is too high to put any additiona
103. lter slot cscccssssssssssseeees 57 Any tips on installing 9Mhz Inrad filters csccsscssscsssssssscsssscssssssssoees 57 Where do I install a 2nd Inrad 9Mhz IF filter sseosseossooesooessooesoossssesssesesose 57 Where can I find more information on filter characteristics s sse0e 57 What are some popular filter combinations esssessoesoessessoesoessessossoossessoesoosse 58 COMPUTER CONTROL ics ciccisccctecsscsctessivactecteenctetsaesctsisir ch cnteeiesiiesteteen 59 How do I wire the IC 746 up for computer control scccccecessecsecesenee 59 What cables do Priel sciicccsiccsticss cessenasecectssiedccouaveccseessivacsosbadeabeyseesveusescecsebuevace 59 What are CT 17 OPC 478 OPC 662 all about sesossossesoosessoseoseesossossesosses 59 Do I need a special cable to connect a CT 17 to an C 746 scssscssseeeees 61 What is the control protocol for the C 746 scssscsssssssecssscssscssssssseenees 61 What IS CIV 2 csisensonescaanseveonncensiayansedegvennecnenangeveptnctussniaeebepsogseskajsiange iasa S 61 What is the CI V address of the 1C 746 sscssssssscssscsssessssessssssssssssseeees 62 What computer software is available sscccsscccscsscscsscccsssecsssessessesseesees 62 Where can I get computer software and upgrades scssccssesssscsssesees 62 Why doesn t computer software update freq when tuning the 7462 65 How do I
104. m group IC746 files Dial zip 6 9 Why don t my band edge beeps match the US amateur bands Nobody knows what if anything the band edge beeps correspond to 6 10 Can I transmit all the way out to the band edge beeps Yes you can transmit all the way out to the beeps The IC 746 as shipped from the factory can transmit outside of the amateur radio bands This has been tested and confirmed on several rigs via dummy loads 6 11 Can I reprogram the band edge beeps No there is no known way to reprogram the band edge beeps There are no fixes or planned updates from Icom dealing with them You can however turn them off entirely 6 12 Do we know anything about the band edge beeps The band edge beeps generate a lot of discussion and speculation As of October 2002 the band edge beeps on all tested rigs both 746 and 746 PRO correspond to 1 8 2 0 MHz 3 4 4 1 MHz 6 9 7 5 MHz 9 9 10 5 MHz 13 9 14 5 MHz 17 9 18 5 MHz 20 9 21 5 MHz 24 4 25 1 MHz 28 0 30 0 MHz If you know of an ANY rig that differs from this then please let us know Rumor has it that the IC 756 PRO and IC 756 PRO II have the exact same behavior Page 74 of 113 2003 02 08 IC 746 FAQ While nobody has figured out what the band edge beeps correspond to we have been able to tule out several possibilities They do not correspond to the amateur radio frequencies in Japan For that matter they do not correspond to the ham alloca
105. mber 2000 issue of QST has a suitable design with feedback in the January 2001 issue On line circuit diagrams based on the QST article appear at http www ambersoft com Amateur_Radio Icom _Interface jpg and http www qsl net civ_commander interface jpg Page 59 of 113 2003 02 08 IC 746 FAQ KD6UU posted detailed schematics and instructions on eham net http www eham net articles 1588 and then wrote an excellent updated follow up article at http www qsl net kd6uu icomci html Designs have been published in both QST and CQ magazines Everything You Always Wanted to Know About Hardware For Computer Controlling Modern Radios Blackburn Wallace AA8DX February 1993 QST p 37 A Low Cost PC Interface for ICOM Radios Thompson Nigel KG7SG July 1992 QST p 37 Far Circuits has some of the required PC boards at http www farcircuits net The actual design of the interface circuit is subject to debate as the above link will make clear Several alternative designs along with a wealth of related information are available from DF4OR s WWW site at http www plicht de ekki civ A few other sources for CT 17 circuit information are http www seed solutions com gregordy Amateur Radio Experimentation CIVInterface htm http www ozleqc dk Downloads htm http www g3ver co uk civ htm The OZ1EQC version of the circuit allows the use of the same COM port for both CT 17 control and RTS styl
106. mods are there for the IC 746 Not all mods are about TX RX frequencies Here are some of the others Note that none of the following modifications were either provided by or approved by Icom These all come from fellow hams Each mod exists for a reason but that reason may not apply to your circumstances Use at your own risk 6Khz wide IF filters W2ENY has devised a way to replace the stock 15KHz or 9MHz IF filters for AM work with 6KHz filters http www geocities com w2eny icom filter htm N9IRD also talks about this type of mod at http www gqsl net icom n9ird html Page 82 of 113 2003 02 08 IC 746 FAQ Safe 2m TX RX Sequencing AH6LE has modified his IC 746 to provide safe sequencing for EME work http www ah6le net radiomods html Simple CAT interface OK2WY has a Simple CAT programming interface for ICOM RIGs Rumor has it that he has also designed an in board step attenuator http www qsl net ok2wy projects htm Separate 2m TX RX Antenna Lines K7YVZ has proposed a mod to the VHF section to provide separate transmitting and receiving antenna ports The details can be found at his WWW site http www qsl net k7yvz 746mod G4YTL describes the same thing at http www mods dk mods php3 radio icom amp model ic 746 amp selectid 1919 1919 WA2TTP Steve reports did that mod recently and it seems to be working OK found a coax jumper in an old Kenwood commercial radio that had the right c
107. ncies The clicking noise you hear is very likely from the relays for the rig s preselector the service manual calls them RF filters At each boundary point the rig switches in a different RF filter There are several 0 1 6 Mhz low pass 1 6 2 Mhz band pass 2 4 Mhz band pass 4 8 Mhz band pass 8 11 Mhz band pass 11 15 Mhz band pass 15 22 Mhz band pass 22 30 Mhz band pass 30 50 Mhz band pass 50 54 Mhz band pass 54 60 Mhz band pass 108 174 Mhz band pass Some mistakenly call this the antenna tuner there is even some component overlap however the preselector and tuner serve different purposes and are each switched in and out accordingly 6 3 Why doesn t the ALC meter work while adjusting the mic gain Despite what the manual says the ALC meter only works for SSB It does not work for FM CW or RTTY Nobody knows what if anything the ALC meter means on these other modes 6 4 Why can t I set numbers into memory names CW keyer etc Use the keypad to enter numbers The dial only does letters and punctuation Page 66 of 113 2003 02 08 IC 746 FAQ 6 5 Why isn t my output power up at 100 watts There are quite a few possibilities Here are a few that have been discovered over the years Low DC supply voltage As shipped the IC 746 really wants a full 13 8 V dc to yield full output power While the rig can operate at voltages as low as 11 V dc power starts dropping off as soon as you drop
108. nd computer remote connectors mislabeled reversed Looking at the rear of the rig the REMOTE Jack is on the left and the SPEAKER jack is on the right Page 68 shows the connections properly Page 9 Incorrect page references Incorrect page references in MENU descriptions at the bottom of the page 4 TCN p 20 should be p 19 7 KEY p 24 should be p 23 8 RTY p 30 should be p 29 9 TON p 35 should be p 34 10 TSQ p 33 should be p 32 Page 15 BAND EDGE BEEPS simply do not work as expected This is more a failing of the radio itself than it is an error in the manual For more info refer to the rest of the FAQ Page 19 SSB TX Tone affects more than SSB The SSB TX Tone setting affects the tonal quality of AM and FM transmissions as well as SSB Page 22 TRANSMIT button does not transmit on CW This is more of a clarification than an error In every other mode AM SSB FM RTTY the TRANSMIT button actually keys the 746 to transmit a signal In CW mode you have to activate the keyer as well Most operators use QSK when operating CW which makes the TRANSMIT button superfluous Page 99 of 113 2003 02 08 IC 746 FAQ Page 27 Only one bar for CW sidetone level not two In the CW gt KEY gt SET menu there are 2 options that control the CW sidetone options 1 and 2 Option 1 sets the sidetone level via the displayed bar However option 2 is only an ON OFF setting there is no level bar contrary to what the manual
109. ndessostendbvencevecsons 100 Page 46 No ALC adjustment for either AM or FM ssssesssesssssessoessossossoesooesoesoeseoesoesose 100 Page 46 Speech Compressor sesssesssecssoossoosssosssoesssosesoossoossosessoesssecssoossoossssessoesssoessoosso 100 Page 53 Enter numbers via keypad not tuning dial sseosseossseossocssoossooesssesssesssosse 101 Page 56 Incorrect Page ReferenceSsS sessecroeseosseesoesooesessoesoossoesoesooesoesoeseossoessossoossessose 101 Page 68 Unclear Voltage Specification ssessseessocesoossoossssesssesssocssoossoosssoesssesssoessoosso 101 Page 70 Overoptimistic SWR Specification eessooesooesoooesooessoesssesssocssoossoossssssssesesosse 101 Page 77 Unclear UT 102 Installation InstructionS ssessoesoeseessoesoesoeseossossoessoesseesoee 101 Page 79 Incorrect SEND Relay Specifications sooessoesssesssesssocssoossoosssoessseessoessoosss 101 Page 84 Incorrect Bandwidth listing scsscsssscsssccsssccssssssscsssscssscssssssssessssssessees 101 SERVICE MANUAL DISCREPANCIEGS 000 cc eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeees 102 Identity of Q302 102 Identity of R1271 102 GEOSSAR Y oie acct eee 103 CONTRIBUTORS ACKNOWLEDGEMENTS sssssnsnnsnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn 105 DISCLAIMER amp COPYRIGHT oo cc ccccccccecccece ecccccececccecesacececd acececesaiscssi acecscecsiicesicasiccus 108 REVISION HISTORY aeeai ai ieden rine coat aaa ce ah c
110. ng is not as effective as traditional IF filtering the 746 PRO instruction manual even eludes to this and that insufficient filtering early on overtaxes the DSP Both are excellent rigs and only time will tell just how effective DSP really is Perhaps someday Icom will make a rig with both Here are some of the features the IC 756 PRO has that the IC 746 does not Dual watch receiver design Real time spectrum scope Additionally the IC 746 PRO retains the basic form factor LCD control layout and bonus 2m capabilities of the IC 746 Page 17 of 113 2003 02 08 IC 746 FAQ Plenty of sales and technical information is available including downloadable pictures and brochures from Icom s WWW site at http www icomamerica com There is a Yahoo discussion group devoted to the IC 7400 as well as a group devoted to the 746 series in general http groups yahoo com group IC7400 http groups yahoo com group IC746 files IC 746pro Instruction Manual 2 pdf Icom has not yet made a copy of the IC 746 PRO instruction manual available in electronic form however the FCC has You can access it and other information at http gullfoss2 fcc gov cgi bin ws exe prod oet forms reports Search_Form hts mode Edit amp form Exhibits amp application id 740578 amp fcc_id AFJIC 746PRO And a nice ham written synopsis appears at http www gqsl net ab4o0j ja7ude ic7400 html http www qsl net ab4o0j icom ic7400 ic7400 html
111. ng it in for repair managed to figure out the bad parts were the D8 and D9 Diodes on the Control Unit They are HSM88AS diodes They are a 3 lead device and look like a surface mount transistor They have C1 indication on the top These diodes are located NEXT to the orange L9 inductor close to the speaker just below the 820pf caps near the open core inductors If you have trouble locating it from the description above you ll either need the manual from Icom to locate the two diodes or have a picture that took is available showing the location Looking at the specs for these diodes http www hitachisemiconductor com sic jsp japan eng products standardics diod lin eup diode eHSM88AS pdf They have a minimum 10 V sub R voltage rating not too high which may explain why they blow so easily but then don t know the signals that they receive under normal circumstances Notice also from the specifications that each part really has 2 internal diodes By looking at the schematic for the radio that comes with your Owners Manual D8 and D9 both have open leads where one diode is NOT used They are on OPPOSITE sides What you can do one time only is to swap D8 and D9 and the radio should work again found that the D8 diode was leaky never did find the D9 diode to be able to measure it notice the warning below HOWEVER this repair procedure is not for the faint hearted These are surface mount parts and are about the size of
112. nnectors ccsscccscssscessessesceseees 90 8 4 What are the pin outs on the ACC 1 connector e ssessseeesooesoossooesssesssosesoosso 91 8 5 What are the pin outs on the ACC 2 conmectOr cccssccsssscccssescessesceeeees 92 8 6 Does audio to pin 4 of ACC 1 trigger the VOX sseeessosssossssssssesssoossoossosssose 92 8 7 Where can I get replacement power connectors cccsccccssssccccrscccssssseesees 92 8 8 Where can I get replacement microphone connectors scccsccccsseseeees 93 8 9 What is Lo Fi SSB Operation os ccciscsesesssccsssssesussecdssecnessovenstsssstnccesenancsenaceess 93 8 10 What is Hi Fi SSB operation cisecsscssccscsessecsoonsescossnsssovesssecessersnesoessseescsessudecs 93 8 11 How does one improve the fidelity of a received signal scccsscssseeeee 94 8 12 How does one improve transmission fidelity e ssooesooesooessssessesssoossoossossssse 95 8 13 Can the IC 746 transmit at less than 5 watts eessoesssesssesssocsssocssoossoosssossssee 95 8 14 How do I turn on both HF pre amps at the same time ssessseessoossoossssesese 95 8 15 How do I adjust the 746 for best AM performance e sesesooessoosssossssesssesesoeee 96 8 16 Is the IC 746 suitable for CAP and MARS operation seessooesooossossssesssesssooee 96 8 17 How do I adjust the Noise Reduction NR eesssesssesssesssoossooesooessoosssoesssesesooee 96 8 18 How do I program a non standard repea
113. o on ignition noise More info on SEND connection problems Added Q A about 60m operation Added Q A about IC 2KL amplifier birdies Added Q A about loose rubber tuning dial grip Added Q A about LCD color Added more info on IF filter characteristics Added more info on building CI V interfaces Added more info on LCD brightness problem Added Q A on internal ATU diode repair Added more info on transmit fidelity Added Q A about ignition noise Added Q A about repeater PL tones Added Q A about possible computer control problems Clarified info about 455K Hz IF filters Added more info about 2nd 9MHz Inrad filters Added Q A about PSK31 hookups Added more info about DTMF generation Added more info SEND relay options Added more info on IC 746 HF Net Added info on 2n TX RX seperation mod Page 109 of 113 2003 02 08 2002 06 03 2002 06 03 2002 06 03 2002 06 03 2002 05 06 2002 04 20 2002 04 07 2002 04 06 2002 03 27 2002 03 24 2002 03 24 2002 03 19 2002 03 18 2002 03 17 2002 03 16 2002 03 08 2002 03 06 2002 03 04 2002 03 04 2002 03 03 2002 03 02 2002 03 02 2002 03 01 2002 02 28 2002 02 27 2002 02 26 2002 02 25 2002 02 22 2002 02 21 2002 02 21 2002 02 21 2002 02 21 2002 02 20 2002 02 19 2002 02 19 2002 02 18 2002 02 13 2002 02 12 2002 02 11 2002 02 10 2002 02 08 2002 02 07 2002 02 06 2002 02 04 2002 02 04 2002 02 04 2002 02 03 2002 02 03 2002 02 02 2002 02 02 2002 02 01 2002 02 01 IC 746 FAQ
114. o prevent the cover from coming into contact with the filter One could mistakenly force the cover closed putting stress on the circuit board causing failure at some point in the future GOHDB has installed an InRad filter this way and can confirm KES5DC s comment about the cover pressing on the filter and thus stressing the circuit board He overcame this by slightly deforming the cover to make it clear the filter the deformation was done very carefully using the rubber coated handle of a hammer It only needs a small amount of extra clearance so the deformation a very slight bulge in the cover is barely visible if you didn t know it s there you d probably never notice it 4 22 Where can I find more information on filter characteristics Here are a few places on the WWW where you can find more information on filter characteristics http www qsl net icom filters html http www qth com INRAD IC 756 HTM http www gsl net ab4o0j icom filters filters html http www qsl net ab4o0j icom passband passband html http www icomclassic com tech_data icom filter rev_a xls Page 57 of 113 2003 02 08 4 23 IC 746 FAQ What are some popular filter combinations Popular does not necessarily equal best Don t do something just because it s popular Read the above material so that you can make an informed choice For example one of the best optional filters for an IC 746 is a 2 4Khz wide crystal filter for the 455Khz IF
115. om W2ENY at http members fortunecity com w2eny tenatuner Operation is similar to that for the other tuners but transmission stops after an 8 second timeout instead of by tuner acknowledgement You can even build this yourself based on the information at http www mods dk mods php3 radio icom amp model ic 706 amp selectid 1864 Don t mind that the info says its for the IC 706 all Icom rigs from this era use the same circuitry connector Page 88 of 113 2003 02 08 IC 746 FAQ Unmuffling Icom Hand Mics WOVD had problems with muffled audio so he opened up all of his Icom hand mics and removed the heavy wad of felt that was in front of the mic elements He s receiving much better audio reports now The felt was probably there to prevent popping from consonants like B or P So beware Page 89 of 113 2003 02 08 IC 746 FAQ 8 Misc 8 1 Are there different versions of the IC 746 Yes there are at least two distinct versions of the IC 746 While most of the indications are circumstantial one definitive piece of evidence are the two different procedures for modifying the transmit receive range Another definitive indication are the 2m differences between the U S Japanese and European versions In Japan the IC 746 has different auto repeater offsets and is limited to only 50w RF output In Europe the IC 746 does not transmit above 146Mhz and has no auto repeater offsets at all There s also a version in
116. onnector on one end and installed a BNC flange mount on the other end mounted the BNC connector to a bracket on the back of the radio the bracket is attached with one 8 32 screw and nut through one of the slots on the rear of the radio The cable passes through the same slot put some shrink tubing over the original plug and tucked it out of the way inside the 746 Seems to work fine with my tower top pre amp and 432 tower top transverter As with all my antennas ran the 746 receive line through my patch panel which makes it easy to disconnect it when not in use also measured a 1 5 db improvement in sensitivity by going directly into the receiver board Finally W8FN Randy says To do this modification you first need to obtain some of the Icom PC connectors used to make internal RF connections The female PC board mount connector is P N 93602690 and the male connector is P N 93602689 About 18 months ago the Icom price was 1 07 per connector ordered six of each figuring I d screw up at least one pair figuring out how to attach the coax to them Icom parts 425 454 7619 option 3 took a phone order and shipped them to me via USPS in just a few days The internal connection that needs to be broken in the radio is the HRX line from CTRL unit J2 to RF unit J1 The source i e the RX line from the T R switch is on the CTRL unit and the RX input is J1 on the RF unit With the radio upside down with the cover off remove th
117. onnectors can be fished through the slots in the rear panel heat sink near the Key jack The assembly with the female PC connector is the T R RX antenna output and the assembly with the male PC connector is the RX input Be sure that you have somehow marked the pigtail assemblies so you know which is Once the pigtails are ready it s time to install them Pull the coax from J1 on the RF board this is the T R switch RX output line Reconnect it to the female pigtail cable assembly Plug the male pin from the other pigtail assembly into J1 on the RF unit To minimize the chances of mechanical problems used plastic tie wraps to bundle the input and output pigtail cables together Once the RF compartment shield is replaced it will hold the cables in place To check your work power up the radio with an antenna connected but no connection to the pigtail jacks You should NOT hear signals in the receiver Momentarily insert the stripped end of a short piece of hookup wire into the RX input pigtail connector you should hear static and possibly signals If all is well connect a short RCA RCA jumper cable between the two pigtail jacks You should have normal receiver function To insert a bandpass filter overload protector etc in the receiver line connect it between the RX antenna out and RX in jacks To use an external receive antenna connect it to the RX in jack Hope this is clear Except for the fiddly process of soldering on the PC connecto
118. ost of the 746 s problems or faults show up either in this FAQ eventually or in one of the archives at http groups yahoo com group IC746 files IC 746 Brochure pdf http mailman qth net mailman listinfo icom 2 3 How does the IC 746 stand up to the Probably the most objective quantitative comparisons you will find are the QST product reviews freely available to ARRL members http www arrl org members only prodrev An Excel spreadsheet that allows side by side comparison of the technical specifications for many HF transceivers can be found at http groups yahoo com group IC746 files HF RIGS xls Simpler more limited comparison charts are available on the Amateur Electronic Supply WWW site at http www aesham com compare comp_hf html User written reviews can be both more personal and more detailed They can also be more biased You can find plenty of them at Page 12 of 113 2003 02 08 IC 746 FAQ http www eham net reviews This topic has come up several times on Yahoo s IC746 discussion group One of the more interesting threads along these lines starts with message 1012 and ends with message 1028 I m told that message 1023 is particularly good Another good thread starts with 1049 and ends with 1077 http groups yahoo com group IC746 message 1012 http groups yahoo com group IC746 message 1023 2 4 Where can I buy sell a used IC 746 Usually when someone asks this on the internet
119. p aade com hampedia prices htm Virtual Hamfest Recent Prices http www vhamfest com prices html site not responding Jan 2002 Ham Shopper http www hamshopper com Good luck 2 6 Is there a dedicated HF net for the IC 746 Yes one was started in October 2001 It convenes 20M SSB near 14 2525 Mhz QRM on Sunday evenings at 9 00pm Eastern time 6 00pm Pacific The folks that run the net shift it along with Daylight Savings Time in the U S A Therefore during standard time last Sunday in October to the first Sunday in April the net starts at 0200 UTC Monday During savings time first Sunday of April through last Sunday of October the net starts at 0100 UTC Monday For the curious not all of the U S A participates in daylight savings time Likewise portions of Europe participate but on a different timetable A wealth of information on DST can be found via Yahoo at http dir yahoo com Science Measurements and Units Time Daylight Saving Time or within the AC6V link indices at http www ac6v com opaids htm CLOCKTIME or directly from NIST the National Institute of Standards and Technology at http www time gov The folks in the Yahoo IC746 e mail group try to maintain a net calendar at http groups yahoo com group IC746 calendar Yes you have to be a member of the e mail group to access their pages but as a fringe benefit you ll even get an automatic e mail reminder on the day
120. pacitor etc from KK5DR Matt Erickson at kk5dr ev1 net Page 38 of 113 2003 02 08 IC 746 FAQ Another good QST article on microphone preamps is Adapting the Astatic D 104 Microphone for use with Modern Transceivers QST Aug 1999 p 34 a copy of which can be found at http members aol com ampmicro Another interesting design can be found at http www muzique com ssm2166 gif 3 3 6 What are the pin outs on the microphone connector As listed on page 67 of the Instruction Manual 1 mic input 2 8V DC Output at up to 10ma 3 freq up down ie 76 4 Main readout squelch switch 2 K o 5 PTT 6 GND PTT 8 AF Out varies with AF center pin a Page 39 of 113 2003 02 08 IC 746 FAQ 3 4 Keyers 3 4 1 Can I hook my straight key to the front Elec Key Jack 3 4 2 Can I connect my own Electronic Keyer to the IC 746 3 4 3 How do wire up my paddles for use with the internal keyer Short Answer Yes virtually any type of key keyer can be connected to the IC 746 via either the front Elec Key jack or the back key jack However the two jacks require different wiring and only the front jack will give access to the internal electronic keyer The front Elec Key jack on the radio accepts a 3 conductor 1 4 inch stereo phone plug and can be wired for use with anything The back key jack accepts a 2 conductor 1 4 inch mono phone plug and can be wired for use with eithe
121. places http www bigskyspaces com w7gj IC 746 pdf http groups yahoo com group IC746 files IC 746 NB Adjustment pdf http www qsl net kb9sss IC 746 IC 746 NB Adjustment pdf 6 19 How do I fix a loose rubber grip from the tuning knob Very few people have had this problem These are the suggestions people have made to remedy the problem e Use a large rubber band e Use a glue stick e Use electrical tape e Use rubber cement e beware that RC might deteriorate rubber e leave set hole uncovered to allow front panel removal e maybe tack just a few places to allow ring removal 6 20 Where should I go for repairs There are lots of places you could go A few of the authorized Icom service repair centers come highly recommended by other hams AVVid http www avvid com Email Clif avvid com AASSH Michael 2101 E Shady Grove Rd Irving Tx 75060 Phone 800 214 5779 Q9AM 6PM CST Mon Fri Local 972 554 6801 KK7TV Communications http www kk7tv com Email info kk7tv com Custom Sound and Video 2350 W Mission Lane Ste 7 Phoenix AZ 85021 Phone 888 767 9997 Page 78 of 113 2003 02 08 IC 746 FAQ Local 602 371 0555 FAX 602 371 0522 Paul Hanson amp Associates Paul Hansen amp Associates 2411 Robert Nash Ct Tucker GA 30084 Phone 770 939 1320 Houston Amateur Radio Supply George Phone 281 355 7373 While not authorized by Icom the following repair shops have
122. ports that his 746 exhibited this problem when he shut the power supply off while the 746 was left on then turned the power supply back on a while later Once on changing the brightness setting would restore the LCD Furthermore when he powers down the 746 before shutting off the main power supply he has no problem 6 8 Is there some way to get the lcom 746 to generate DTMF tones No The IC 746 will not generate DTMF tones However you have some options for generating DTMF tones yourself The good news is that Icom s compatibility table shows that the HM 14 DTMF hand microphone will work with the IC 746 It even comes with a handy switch to enable disable the UP DN buttons if only the buttons would work Remember you have to press the PTT switch to use the DTMF pad The bad news is that the HM 14 is a discontinued item so availability is limited Also as K9HFX discovered there are apparently two versions of the HM 14 The version without the scan button enable disable switch did not work for him More information is needed While not listed on Icom s compatibility charts as such VE2MHF reports that the HM 56A also works even the scan buttons and 14 DTMF memories However beware as VE4HAY reports that the DTMF pad on the HM 56 will also work with the IC 746 but it s scan buttons will not We have to be careful of the exact model numbers Icom confirms that the HM 118T will work with a suitable wired adapter There is also specu
123. quire cabeling or a change in procedure Remember the transceiver s internal ATU must always be disengaged when driving an external tuner Cascading tuners can reflect high reactance values back into the internal ATU and or LPF As a result dangerously high RF voltages can appear across capacitors in these networks leading to component failure Icom s cabling to their own antenna tuners takes care of the above automatically There are too many possible automatic ATUs to cover in this document but here are a few that merit special comment AT 500 The AT 500 in intended for use in the shack with near resonant antennas It is documented as handling mismatches of up to 3 1 SWR but in practice can do better than that particularly at lower power levels It s rated for 500w 160 10m The hard part to using this tuner is finding an OPC 118 interface cable they re not made anymore W2ENY has a clone available at http members fortunecity com w2eny icom_opcl 18a Page 32 of 113 2003 02 08 IC 746 FAQ AT 180 The AT 180 is intended for use in the shack with near resonant antennas it will tune a maximum excursion of 3 1 The AT 180 was designed for the ham bands only but should have sufficient band overlap to accommodate the MARS frequencies Here are the AT 180 specifications http www icomamerica com amateur hf at 180 html No real point to using this ATU over the built in one AH 4 The AH 4 is an automatic antenn
124. r 100W on 14100khz R991 for 100W on 51000khz and R993 for 100w on 145000khz mode set to RTTY rf power pot set fully c wise pots on main unit board the board with the filters on That s three specific adjustments to cover all 11 bands Check the power output on 20m first Contrary to what the instruction manual implies the alignment does not specify 100w on all bands Expect higher power on lower HF bands and lower power on higher HF bands 6 6 How low can the IC 746 supply voltage be Well page 69 of the Instruction manual says the supply voltage can range from 12 15 Vdc Whereas page 84 says 13 8 Vde 15 which is about 11 7 15 8 Vdc Despite what the manual says some IC 746 s run at voltages as low as 11 0 V de The highest drop out voltage reported so far has been 11 4 V dc Be aware that while the IC 746 will operate at lower voltages it does so at reduced power The power roll off starts at about 13 4 V dc as evidenced from the measurements shown at Page 69 of 113 2003 02 08 IC 746 FAQ IC 746 Power Output vs Input Voltage The above chart is available on the WWW at http groups yahoo com group IC746 files IC746 Power jpg 6 7 The backlight in my LCD has stopped working What s wrong Short Answer Your problem is probably one of the display driver transistors on the S Logic board behind the display It will have to be replaced There is reason to believe but no proof that settin
125. r a straight key or an external keyer but not for the internal keyer See page 68 in the operator s manual for wiring details and pages 23 and 27 for the programming details Long Answer FOR A STRAIGHT KEY OR EXTERNAL KEYER For a diagram on how to wire the stereo plug see page 68 of the Instruction Manual For a straight Key or keyer wire only the tip and the Sleeve and leave the ring as No Connect tip ring sleeve 0000 gt 2 cond wire to key keyer nc The back key jack is a mono 1 4 inch phone plug and is easy to wire When using the front Jack You also have to set the radio to recognize that the ring is not used To set the radio You do have to go to the key set menu and tell it you will be using a straight key See Page 23 and page 27 in the operation manual While in CW mode press KEY F4 then press SET F5 Press the down arrow F2 until you reach the sixth menu KEYER TYPE Use the Main tuning knob to set the type of keyer to Straight Key TO USE THE BUILT IN ELECTRONIC KEYER WITH PADDLES Wire the 3cond Stereo plug use the front jack so that the Dit is the tip the Dash is the ring and the sleeve is common You can also wire up a bug this way without electronic keyer Page 40 of 113 2003 02 08 IC 746 FAQ tip ring sleeve OOOO gt 3 cond wire to paddles dit dash m To set the radio to use the internal electronic key
126. really need an external amplifier switching relay sscssscssseesees 43 Why do I need an external amplifier switching relay e ssecssesoeseessoesoeseeseoe 43 My SEND relay seems to be stuck what do I dO seesseoesooesoossssesssesssosesoosso 47 Where can I get an external switching relay eesssoesssesssesssecesoossoosssssssoeesssee 47 Page 4 of 113 2003 02 08 3 6 3 5 8 3 5 9 3 5 10 3 5 11 3 6 1 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 4 10 4 11 4 12 4 13 4 14 4 15 4 16 4 17 4 18 4 19 4 20 4 21 4 22 4 23 5 1 5 2 5 3 5 4 5 5 5 6 5 7 5 8 5 9 5 10 5 11 5 12 IC 746 FAQ Can t I just use the ACC port to key my amp seessoesssesssesssocssoocesooesoossssessoee 48 How do I build my own SEND relay isolation circuit relay esssesoossessoeseosse 48 Why do I get IC 746 birdies when I turn on my IC 2KL e seseessesssessossessoe 49 How do I hook up a Yaesu Quadra VL 1000 amp to an IC 746 49 Dl Lee E E E eee ee ieee A eee 50 How do I hook up a TNC to the IC 746 eeesssessseosseossoossoossoosssossssesesoossoossosssose 50 ca El ne em i cen oe ERE ERE en MERU ER ENE noe 51 How many optional IF filters can I install into the C 7462 sscssssssees 51 What optional IF filters are available for the C 746 ssscsssssssssssenees 51 Which optional IF filters should I Duy scccsscccsssecscsscccsscsccssescsssescesees 52 W
127. rime factor Inrad filters tend to outperform the Icom filters for this application For example the stock Icom filter in the 455Khz IF has a 6db bandwidth of 2 4Khz and a 60db bandwidth of about 5Khz That gives it a shape factor of approximately 2 1 The comparable filter from Inrad has a shape factor of 1 6 a 6db bandwidth of 2 4Khz and a 60db bandwidth of 3 8Khz This all means that the Inrad filter has a steeper attenuation curve resulting in better extraneous signal rejection and improved selectivity The Inrad filters tend to have greater ultimate attenuation than the Icom counterparts Thus Inrad filters tend to do a better job of adjacent signal rejection than Icom s filters However while the 455Khz Inrad filters are drop in replacements for the Icom counterparts the 9Mhz filters are not They need a short piece of coax and a connector to wired up to the filter first The adapting connector plugs into the filter slot thus alleviating any mods to the Page 54 of 113 2003 02 08 IC 746 FAQ radio itself Reported assembly times range from 1 4 hours per filter depending upon the skill and care of the installer Finally some claim that there is an insertion loss to the Inrad filters vs the Icom filters However it s been demonstrated that dropping the noise level also drops the S meter reading possibly accounting for the reports Bench tests do not show any insertion loss Your ears may vary eHam net has several us
128. roup IC 706Mk2G http groups yahoo com group IC 756PRO http groups yahoo com group ic756pro2 http groups yahoo com group IC Q7 http groups yahoo com group IcomRadio IC 751 information pages http www sweb cz ok1fig ic751la htm http www qsl net ab4oj icom 751a_pbt html http www qsl net ab40j icom icom html IC751A http www piexx com cgi bin piexx cgi p ICOMProm amp cart_id 1452031 27134 http www piexx com cgi bin piexx cgi p uxl4 amp cart_id 4031494 24744 IC 765 information pages http www execulink com dstalk Last but certainly not least AC6V has a wealth of links and resources on amateur radios http www ac6v com swap htm 2 16 What articles have been written about the IC 746 Add Remote Control to your ICOM Transceiver Hansen John W2FS February 2003 QST p 41 Adapt a mundane infrared TV remote to control your rig ICOM IC 746PRO HF VHF Transceiver product review Lindquist Rick NIRL May 2002 QST p 72 A product review article http www arrl org members only prodrev pdf pr0205 pdf Page 19 of 113 2003 02 08 IC 746 FAQ A Microphone Adapter for the IC 706 Davidson Taylor N4TD May 2002 QST p 38 Describes a microphone preamp control project that could be easily adapted to the IC 746 A Quality Sound Card Interface for ICOM Rigs Lewis Bob AA4PB March 2002 QST p 31 A great way to capitalize upon the ACC ports Feedback in May 2002
129. rs the procedure is really pretty easy Let me know if you need further assistance Increased MONITOR Volume Unhappy with the volume level of the MONITOR some have tried placing a 4 7K resistor in parallel with R1087 to raise the level There are more details on the www mods dk site at http www mods dk mods php3 radio icom amp model ic 746 amp selectid 2299 LCD Driver Transistor Replacement Some folks have replaced the transistors that drive the LCD backlight in an attempt to prevent overloading and burnout See the question devoted to LCD lamps repairs for all the gory details Page 84 of 113 2003 02 08 IC 746 FAQ Poor Man s TCXO NOUK Chris came up with a poor man s TCXO that substantially reduces frequency drift particularly for 2m He discovered that the cooling fan which runs during transmit draws air right across the local oscillator The resulting temperature drop causes the LO to drift He stuffed the 60 Mhz LO compartment with a few cotton wool balls as insulation It doesn t eliminate drift entirely but the improvement is dramatic The original e mail message on this is at http groups yahoo com group IC746 message 1959 A WWW site describing the mod complete with pictures is at http www chris org Modifications IC 746 almost free tcxo html Upgrading Stock Ceramic IF Filter to a Crystal Filter The stock 455 Khz IF filter is a 2 4 Khz wide ceramic The PC board is drilled and traced for a full fle
130. rticularly important for CW and digital modes Smaller tighter shape factors reject more noise and improve selectivity Larger wider shape factors generate fewer problems complaints with fidelity or ringing 4 7 What is considered to be a narrow filter In the context of and for the purposes of this FAQ a narrow filter is any filter that has a smaller bandwidth than the stock 2 4Khz wide filters However most texts will describe a filter as being narrow if its bandwidth is smaller than that of the desired signal 4 8 What are narrow IF filters used for Usually narrow filters are used to reject unwanted signals or noise The narrower the bandwidth the less noise there will be and the better the sensitivity You can lose part of the desired signal in the process but that may be preferable to the interference you re trying to reject Page 53 of 113 2003 02 08 IC 746 FAQ 4 9 Can an IF filter be too narrow Yes an IF filter can be too narrow but sometimes that can actually work to your advantage We ll describe only a few specific situations as examples When the IF filter s bandwidth is less than the bandwidth of the desired signal then part of the signal will be rejected This degrades the fidelity quality of the received signal In phone modes the fidelity loss is often mistakenly perceived or described by operators as distortion Fortunately the inherent information redundancy of human speech allows it to be re
131. s Added M E P 22 TRANSMIT button on CW Added Q A about using both preamps Updated Q A on electronic manuals Added info on cotton wool ball mod Added Q A on transmit fidelity pdated Q A on receive fidelity pdated info on 746 NET pdated info on power supplies pdated info on 746 mods GE asa pdated Q A about magazine articles pdated freq for HF net pdated info on wiring dynamic microphones pdated info on IC 746 PRO Added Q A about PDF font error Added Q A about magazine articles Checked and added more manual page references Added M E P 42 15Khz filter at Mhz IF Added M E P 56 use keypad for numbers Added M E P 46 COMP GAIN control Added M E P 15 band edge beeps Added M E P 68 confusing ALC voltage Added M E P 46 ALC only on SSB Minor updates regarding SWR values Added M E P 70 SWR fold back Added M E P 79 SEND relay limits Updated Q A about electronic manuals Added M E P 32 No ALC for FM Added M E P 6 speaker remote jacks swapped Added M E P 56 incorrect page reference Added M E P 33 incorrect page references Added M E P 9 incorrect page references Added M E P 2 incorrect page reference Added M E P 77 UT 102 installation Added section for Manual Errata More info on IC 746 net and daylight savings time More info on MARS mod by Icom Added Q A about microphone pin outs Separated Q A on mods into three Q A More mods information Updated info on DTMF microphones Gaaa Added
132. s claim to fame is selectable skins You get to choose what you want your radio to look like be it IC 746 IC 706 or even a 007 spy watch More details at http n9zle tripod com ScanCat Very extensive scanning support including automatic digital recording to your hard disk http www scancat com Radio Manager An example of the virtue os simplicity this shareware from KCSIRJ does a lot with minimal resources http www interplaza com bensware rmm32 htm http www leader it shareware info 00088 html Zakanaka This and a logger was written by K4CY http www gsl net kc4elo Icom Pro Memory Edit Small program that allows editing and organizing all of the memories in any of the 746 756 series including the CW keyer memories Page 64 of 113 2003 02 08 IC 746 FAQ http www plicht de ekki software pme html MixW http tav kiev ua nick mixw mixw htm 5 10 Why doesn t computer software update freq when tuning the 746 CIV Transceiver when enabled forces the radio to report its frequency whenever you QSY and to report its mode whenever you change mode via a front panel button Make sure you ve set this option in the IC 746 if your software supports it With CIV Transceiver not enabled rig control software must periodically poll the radio to determine its current frequency and mode When using this mode make sure you have set your software s polling rate accordingly 5 11 How do wire up
133. shows Page 32 No ALC adjustment for FM In FM Operation under TRANSMITTING section 5 it states Push TRANSMIT and adjust the MIC GAIN so that the ALC level in the ALC meter stays in the ALC zone when speaking into the microphone The ALC meter is maxed out on any setting of the mike gain and has no meaning or effect under FM ALC adjustments made in SSB carry over modes Once you get the audio drive level adjusted for proper SSB modulation then the audio drive level ends up being right for all the other modes as well Page 33 Incorrect filter diagram The diagram at the top of the page is incorrect It shows only one stock filter 2 4 Khz wide at the 9Mhz IF There is a second 15Khz wide filter at that point instead of the direct through connection shown Page 42 Incorrect Page Reference Reference for Noise reduction p 39 should be p 40 15Khz filter at 9Mhz IF Page 46 No ALC adjustment for either AM or FM In the Speech compressor section the ALC meter doesn t appear to work on AM ALC adjustments made in SSB seem to carry over to other modes Once you get the audio drive level adjusted for proper SSB modulation then the audio drive level ends up being right for all the other modes as well Page 46 Speech compressor The Speech compressor instructions fail to make clear the fact that both the MIC GAIN and COMP GAIN controls will have to be adjusted for proper operation Page 100 of 113 2003 02 08 IC
134. ss and let the internal ATU do its thing For troublesome bands antennas they turn off the internal ATU and engage the external one Others use an external ATU to match their antenna to the middle of the desired band and let the internal ATU handle the rest In theory the ATU doesn t know or care what s hooked up to it it simply tries to match up to the impedance it sees In most cases either of the above approaches work fine Many hams have been applying both for years with no problems However some IC 746 s have had their ATUs go out from fried detector diodes and driver transistors On many repairs Icom has blamed the failure upon external tuners One ham was told that external tuners can cause problems even when they are switched to bypass Nobody has been able to adequately explain why an external tuner would cause such damage particularly when bypassed Some speculate that tuning with low power is safer than tuning with high power if nothing else its at least more polite We need more information on this but at least you ve been warned The best procedure we can suggest at this point is e Turn off the internal ATU e Reduce power to about 1 4 25w e Adjust the external ATU using the rig s SWR meter The two meters usually disagree It is what the rig sees that is important e Restore full power e Turn on the internal ATU Do not adjust the external ATU at full power Do not adjust the external ATU while the AT
135. ssessssesssee 29 Are there any tips to using the ATU e seessessoesoessessoesoossessoesooesoeseossoeseeseossoe 29 Can I use the internal ATU along with an external ATU sccssssssseeees 29 Does the internal ATU work on receive scssccssscsssessrscsssscssscssssscseesees 30 Any other gotchas with the internal ATU sessessessoesoossessoesoossossossoossossoesooe 30 How do I use a beverage antenna e sseecsooessosssocsssesssocessoossoossoosessesssesesoose 31 How do I use different antennas for receive vs transMit scccscsssesees 31 Split VFO Meho e A A E a ears NE 31 External Antenna Switcher Method s sessssessessesseessessessressessresrresseserssressesse 31 External RF Sense Antenna Preamp Method ccccccccseceseceeeeeeeeeeeeeeeeneeenees 31 How do I measure SWR while in SSB ssccssssssscsssscssscssssscsesssesssssssseneees 31 How do I tune up in CW without a Key eeesssessoesssoesssesssecssooesoossoosssoesssocssoosso 32 What about using an external automatic ATU ssesssesssesssesesoossoosssosessssssese 32 Can the TUNER button activate an external automatic ATU ccceee 33 Why doesn t the rig SWR meter match my external SWR meter 34 Which SWR meter should I trust internal or external cssccssssesseeee 34 How do I repair the detector diodes in the internal ATU sscssssssseeees 35 How do I switch between more th
136. t voltage booster system from W4RRY that should do the job Check out http www fastg com w4rry You have an IC 746s instead of an IC 746 The s variation on the IC 746 is limited to only 10 watts output power to match up with the restrictions of one of the Japanese amateur radio license classes Blown Internal Fuse Check the 5A fuse within the RF power amplifier of the C746 reference page 81 of the instruction manual If this fuse is blown there will be little to no output lt 10w There has even been a case of an intermittent fuse Outside the rig with a multi meter the fuse would test OK However replacing the fuse still fixed the problem Page 67 of 113 2003 02 08 IC 746 FAQ The RF driver transistors may have failed The driver stage is common for 2 meters and HF The two driver transistors 2sc1972 are right under the top cover You can easily measure the voltage on the basis or feel the temperature of the 100 ohm basis resistors 2SC1971 transistors are much cheaper than 2SC1972 transistors and are used in the common pre driver but can only provide half the power 50 watts If your rig is used then it s possible though not likely that a previous owner did a repair using the wrong part Replacing these parts are not for the faint of heart Have the service manual on hand and be prepared to readjust realign everything afterwards Don t try to replace the transistors without a safety resistor
137. t an external switching interface This is often a hotly debated topic that has left quite a few blown out rigs in its wake It is possible to run an amplifier without a switching interface The article at http www gsl net icom keynotes html tries to describe the necessary conditions 3 5 5 Why do I need an external amplifier switching relay Short Answer It s far too easy to overload and damage the internal switching relay resulting in expensive and or annoying repairs The external isolation relays are cheap insurance for our rigs Even Icom technical support recommends them Long Answer Given that the relay is prone to overload the natural question that arises is just how much can it handle Things get both lengthy and muddy from this point on but since you re still reading we ll press on Remember you were warned Page 43 of 113 2003 02 08 IC 746 FAQ This continues to be a process of discovery so I ll present what we know in that form Instruction Manual Page 79 of the instruction manual says that the SEND jack is rated for 16 Vdc at 2A Some rigs have failed while well within those specs Others seem to survive conditions far in excess of that rating Obviously the ratings in the manual don t tell the full story Homebrew explanations and solutions for the problems abound Some talk about bypass capacitors while others talk about suppression diodes Folks debate inductive vs resistive loads and ratings Surge
138. t does both SEND and PTT functions You ll need to account for that in your design One example of a relay based design complete with suppressor diode bypass capacitor and limiting resistor can be found at http www qsl net kk5dr IcomKeylInterface html Rumor has it that Matt will even build it for you for a fee of course But then you wouldn t have built your own would you One example of a solid state design originally intended for a Kenwood but easily adapted to an Icom can be found at Page 48 of 113 2003 02 08 IC 746 FAQ http www qsl net kObx amp html Another example is here http www k6xx com radio ic706amp pdf And yet another example http www yccc org Articles AL1200relay html 3 5 10 Why do I get IC 746 birdies when I turn on my IC 2KL The IC 2KL is at fault not the IC 746 A noisy 12 volt switching supply within the IC 2KL causes the problem The supply is in a small shielded box on the top of the chassis behind the meter Cleaning and tightening the metal box and covers will help Additionally Icom recommends changing out leaky bypass and filter capacitors 3 5 11 How do I hook up a Yaesu Quadra VL 1000 amp to an IC 746 The RF ALC and SEND connections are pretty straightforward The only truly tricky part is getting the band select data from the IC 746 to the VL 1000 Fortunately AB40J Adam has already forged the way The details are at http www qsl net ab40j qua
139. t is still appliccable Everything You Always Wanted to Know About Hardware For Computer Controlling Modern Radios Blackburn Wallace AA8DX February 1993 QST p 37 Computer control interfaces for several makes and models of transceivers including Icom http www arrl org members only tis info pdf 9302037 pdf A Low Cost PC Interface for ICOM Radios Thompson Nigel KG7SG July 1992 QST p 37 One of the early original designs for a homebrew CI V interface How To Build A Super Simple Computer Interface For The Kenwood TS 440S And ICOM IC 735 Brown Paul NF2B March 1992 CQ p 42 One of the early original designs for a homebrew CI V interface 2 17 Can I transmit 100w at 100 duty cycle on CW SSB RTTY PSK etc Yes All of the 746 756 series were designed to handle continuous 100w output in all modes The rig will get quite warm and the fan will run continuously Be sure you allow adequate ventilation Page 21 of 113 2003 02 08 IC 746 FAQ 2 18 I thought the LCD was blue but photos show it as green The screen is blue The green color that shows up in many photos is caused by the camera flash sort of an optical illusion Non flash photos always show the screen as blue For an example see N4WMX s 746 non pro at http www backroadadventure net gallery Radio aaj 2 19 Can the IC 746 work on the 60m band 2 20 Can the IC 746 work on the Alaska Emergency Frequency Yes no no and yes To both q
140. t kb9sss IC 746 IC 746 Instruction Manual pdf Additionally the FCC posted the IC 746pro instruction manual and various other documents at http gullfoss2 fcc gov cgi bin ws exe prod oet forms reports Search_Form hts mode Edit amp form Exhibits amp application id 740578 amp fcec id AFJIC 746PRO Backup copies of both parts of this manual are also available http groups yahoo com group IC746 files IC 746pro Instruction Manual 1 pdf http groups yahoo com group IC746 files IC 746pro Instruction Manual 2 pdf Another good place to look for on line manuals is http www mods dk Hey we even found a copy of the IC 746 Instruction Manual in Italian http www marcucci it download While Icom has relaxed a little in providing these documents they are still protected by copyright Please treat them accordingly Remember Icom is doing us a favor 2 8 Are there electronic copies of the circuit schematics We know of some for the IC 746 PRO but not for the IC 746 Check out Page 15 of 113 2003 02 08 IC 746 FAQ http hamradio online ru sch_eng html for a wide variety of schematics 2 9 Are there electronic copies of 746 service manuals No such copies are known to exist although they would quickly become popular if they did As of May 2001 Icom had no plans for releasing one Additionally Icom considers any such external productions to be a violation of their copyright Ray the product mana
141. t of 10 20 watts is about right for 100 watts PEP Processed speech will have a high average value and the meter will read higher of course A loud tone or whistle will read higher yet A lot depends upon the characteristics of the meter Some meters will follow voice peaks better than others Page 68 of 113 2003 02 08 IC 746 FAQ Try setting option 10 Meter Peak Hold to give you a better idea of your peak power output Or better yet monitor your output on a scope with a standard two tone test There are excellent instructions on using an oscilloscope to make PEP measurements at http www qsl net ab4oj peptest html If you conclude that you have an audio feed level problem then try increasing the microphone gain or turning on some compression CW Break In Turned off When the rig is receiving and Break In operation is turned off the rig will generate a sidetone even though it is not transmitting While this is good for tuning and CW practice it can fool you into thinking that there is no RF output Check your settings and make sure you really are transmitting perhaps switch to RTTY mode and see if you get any output Internal adjustments set a little low Apparently many IC 746 rigs were factory adjusted with lower RF outputs of about 80 90 watts If the fractional db of power is important check out the power adjustment instructions in the mod section of this document The service manual specifies setting R989 fo
142. t will put an undue and possibly fatal strain on your output transistors Page 28 of 113 2003 02 08 IC 746 FAQ 3 2 2 What range can the automatic antenna tuning unit ATU handle Officially the automatic ATU in the IC 746 can handle SWR mismatches of up to 3 1 on HF and up to 2 5 1 on 6 meters In practice many people get even wider ranges a few as high as 7 1 but be wary of pushing the ATU that hard The ATU does not function on 2 meters Some have pointed out that even though the internal tuner may tune a particular antenna configuration if there is a high SWR you could end up burning out the tuner We have at least one case reported by KG6GLN where the detector diodes in an IC 746 were fried According to the ICOM tech it could happen if you tried to use an external antenna tuner in conjunction with the internal tuner 3 2 3 Will the internal ATU handle random wire antennas 3 2 4 Will the internal ATU handle long wire antennas No You ll need an external ATU The internal ATU can only handle an SWR mismatch of about 3 1 on HF and 2 5 1 on 6 meters Such antennas will exceed those limits somewhere over stressing the ATU and possibly blowing it out Matching will be hit or miss mostly miss Of course there s always an exception N4EUK reports successfully tuning his 100 foot wire antenna using the internal ATU Even he was surprised 3 2 5 Are there any tips to using the ATU You mean besides the
143. tches per dit dah So CW at 1 wpm will generate 30 relay operations per minute That s the limit of what the relay can handle at full load 10 wpm will generate 300 op min which is the no load limit for the relay 30 40 wpm what my local CW contesters do pushes us to about 1 000 op min which is well beyond the relay s rating The max internal keyer speed of 67 wpm as per ARRL review would yield a brutal 2 010 op sec This could account for the varying results encountered in the field We d all assumed till now that the problem was simply one of current or voltage overload Now we can see that those operating QSK CW are overstressing the part no matter what the load Pushing the part that far beyond its operational limits would certainly make it more failure prone which could explain some of the failures that have happened within the supposed current limitations Expected Lifetime Consider this CW at 20 wpm would generate about 600 op min which would reach the expected mechanical life of the part after less than 3 000 hours of transmitting But wait if we apply that same rate to the expected electrical life we get less than 30 hours of transmitting time In contrast AM FM SSB RTTY operation would likely require 200 000 to 2 000 hours respectively of operating time to hit either expected lifetime The Schematics The schematic on page 11 4 of the Service Manual shows the SEND relay as an AHY103 not the OMR 109F listed in the Par
144. ter Offset sccsssecsssssssessees 97 8 19 How do I turn on repeater PL tones eessssoessoessossssesssocesooesoosssoesssecssoessosees 97 8 20 How do zero beat a CW signal sessseessecssooesooesoosessesssocesoossoosssoessssesssesesoese 98 INSTRUCTION MANUAL ERRATA ssssnnaansnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn nnne 99 Page 2 Incorrect Page References e ssesescseercesoseseseseososcscecesoseseseesososeseososssososeseesesesesee 99 Page 6 External speaker and remote interface jacks are swapped scccssesessees 99 Page 9 Incorrect page references eesssesssecssocssoossooessoesssesssoesssoessoossoosessssssesssosssoossossses 99 Page 15 BAND EDGE BEEPS simply do not work as expected ssoesssesssesssosssooss 99 Page 19 SSB TX Tone affects more than SSB se ssesssooesooessoesssesssecssocssoosssossssesssosesooseo 99 Page 22 TRANSMIT button does not transmit on CW e ssessoesoesseseoesoossessossoossessoesossse 99 Page 27 Only one bar for CW sidetone level not tW0 esesooessoesssesssesssocssoossoossssesssee 100 Page 32 No ALC adjustment for FIM ssscisessssecssssoectssecscsssepessensssanesestenensscsssenabarenseseenases 100 Page 33 Incorrect filter dia rami sii ssejsessccuseccstesssncssseesdsosaseeconcossecessossadsverseecoussstancsesenss 100 Page 7 of 113 2003 02 08 IC 746 FAQ Page 42 Incorrect Page Reference wx siccesssccicsscasesscnsesscecenncassosteccbseueisseson
145. the IC 746 for use with PSK31 The simplest way is to buy an interface There are several available some examples are BUX CommCo http www buxcommco com Donner s Digital http home att net n8st West Mountain Radio http www westmountainradio com Or you could build an interface You ll need audio in audio out and PTT signals Several DIY plans are available http www qsl net wm2u interface html http www gsl net wm2u psk3 1 html http www arrl org tis info HTML psk3 1 index html http www w5bbr com soundbd html http home teleport com nb6z psk3 1 htm http www psk31 com Hook_it Up hook_it_up htm 5 12 Why isn t my computer control working There are MANY things that could be wrong Here are a few of the things you can check e Computer s serial port baud rate e Computer s serial port address e Interconnect wiring e Make sure the 746 CI V address 28 in the 746 menu is set for 56h e Make sure the 746 CI V baud rate 27 in the 746 menu is set to AUTO e Make sure the 746 CI V Transceive 29 in the 746 menu is set to ON e Make sure the 746 CI V 731 Mode 30 in the 746 menu is set to OFF Page 65 of 113 2003 02 08 IC 746 FAQ 6 Problems and Clarifications 6 1 What s that funny rattling noise hear when first power on Often it s the internal antenna tuning unit The relays make audible clicking rattling sounds 6 2 What s that click I hear as tune across certain freque
146. the WWW links Added Q A about keyless tuning in CW mode Updated mod Q A to add tx rx sequencer Minor addition to transmit fidelity Q A Added Q A internal external SWR readings Added Q A on measuring SWR in SSB Added Q A about popular filter combos Added another IF filter passband link Added info on A suffix IF filters Updated Q A s on microphones Added several Q A s on amplifiers Reformatting of some manual errata Added M E P 27 CW sidetone level Page 110 of 113 2003 02 08 2002 02 01 2002 01 31 2002 01 31 2002 01 21 2002 01 12 2002 01 11 2002 01 10 2002 01 09 2002 01 08 2002 01 07 2002 01 06 2002 01 05 2002 01 04 2002 01 03 2001 12 31 2001 12 31 2001 12 31 2001 12 28 2001 12 18 2001 11 29 2001 11 26 2001 11 20 2001 11 19 2001 11 16 2001 11 13 2001 11 10 2001 11 09 2001 11 09 2001 11 09 2001 11 09 2001 11 08 2001 11 08 2001 11 08 2001 11 08 2001 11 07 2001 11 07 2001 11 06 2001 11 06 2001 11 06 2001 11 06 2001 11 06 2001 11 06 2001 11 05 2001 11 05 2001 11 03 2001 11 02 2001 11 01 2001 11 01 2001 11 01 2001 11 01 2001 10 30 2001 10 30 IC 746 FAQ Added M E P 19 SSB TX Tone affects AM FM Added Q A about CAP MARS compliance Added Q A about future of FAQ Updated info on 746 NET Rearranging and updating mods info Added info on cordless headset mod Tested and updated all links Added Q A on Noise Blankers Added Q A on adjusting AM performance Added Q A about tuning click
147. tions in any of the IARU regions They are not a combination of all available amateur radio from around the world i e a minimal superset They are much wider than that As wide as the band edge beeps are they do not encompass all of the MARS Military Affiliated Radio Service or CAP Civil Air Patrol frequencies To do that still requires a mod The known TX mods do not affect the band edge beeps Anybody have any other ideas or info 6 13 How I reset back to factory default settings The procedure is listed on page 81 of the Instruction Manual as well as on Icom s WWW site at http www icomamerica com support cpureset html amateur While pushing in F INP and M CL push POWER to turn power ON 6 14 What birdies does the IC 746 have Birdies are spurious signals internal inherent to the rig itself They are normally generated by harmonics and or mixing products of the internal oscillators IF VFO display driver CPU clock etc that are picked up by one of the RF IF stages of the rig Birdies are usually perceived as silent carriers on AM and FM and as steady tones on SSB and CW sort of like someone tuning up on that frequency Thus the perceived frequency of occurrence is affected by your preferred sidetone Often local noise sources can be mistaken for birdies True birdies tend to be consistent from rig to rig The following frequencies have been submitted as possible birdies There have not been enou
148. ts List on page 6 12 this is listed in the Manual Discrepancy section of the FAQ Currently we believe that the parts list is correct and that the schematic is wrong However this might help explain why Icom Tech Support has quoted different specs at different times Mysterious Successes OK To be totally fair there are some amps out there that seem to work OK without an isolation switcher Alpha Power for example uses an IC 746 daily to test their Alpha 99 series of amplifiers They report no problems Off course their 25 Vdc exceeds Icom s specifications but are within the relay specifications Go figure Connection Confusion So far we ve concentrated upon the SEND jack on the back of the rig There are also HSEND and VSEND signals available via the ACC connectors What makes matters worse is when some folks mistake these signals for the relay driven SEND line when in fact they Page 46 of 113 2003 02 08 IC 746 FAQ are driven by transistor Q1302 The transistor is not a hardy as the relay with obvious consequences Summary We have now identified MANY possible failure conditions for the SEND relay Too much voltage Too much current switching or carrying V C spiking from inductive loading Accidental AC operation Exceeding operational rate Exceeding expected lifetime Connection confusion amp amp Those are the reasons for using an external SEND relay 3 5 6 My SEND relay seems to be stuck
149. tting in and out There are several possibilities e Check your RF Gain Squelch settings the squelch could be kicking in e Check your headphone jack it may have an intermittent contact causing problems Page 81 of 113 2003 02 08 IC 746 FAQ 7 Modifications 7 1 What TX RX mods are there for the IC 746 mod is slang for modification Most people who ask about modifying their radio are looking for ways to make the IC 746 transmit or receive additional non amateur RF bands The 746 already has general receive coverage from 0 5 to 60 0Mhs so no mod there Modifying the IC 746 to transmit outside of the amateur bands is generally considered to be illegal There are a few exceptions like perhaps MARS CAP transverter usage changes additions to ham bands etc but they can become controversial Icom will give you the correct mod for your IC 746 based upon your serial number providing you give them a copy of your MARS license to prove eligibility If you let Icom make the mod for you small fee plus shipping then the mod will not void your warranty That said MARS CAP TX RX modifications for the IC 746 and many other radios can be found at http www mods dk Another source for the TX RX mods is QRZ COM http www qrz com download mods i k ic746 txt Pay close attention as there are two distinct mod procedures which correspond to the differing placement of the programming diodes on the PCB 7 2 What other
150. uestions For the purposes of our discussion the Alaska Emergency Frequency of 5 1675 MHz USB can be treated as part of the 60m band Yes the IC 746 can receive the 60m band and does so quite nicely No as shipped the IC 746 will not transmit on the 60m band No there is no 60m specific mod to the rig Yes there is an all band mod that will allow the IC 746 to transmit on the 60m band See http www mods dk Of course once you ve opened up ALL of the bands this way appropriate caution is dictated The IC 756 original not the pro has a very similar design to the IC 746 Some IC 756 users report an output power dropoff near 5 MHz presumably due to the output band pass filters Anonymous reports indicate that the 746 does not suffer the same problem I do not have any data on the 746 PRO Page 22 of 113 2003 02 08 IC 746 FAQ 3 Accessories 3 1 Power Supplies 3 1 1 What power supply should I use with the IC 746 Short Answer Any good quality communications grade power supply rated at least 20 amps or more continuous duty should do just fine However most of us use larger supplies for a variety of reasons Popular supplies that are known to work via testimonial Alinco DM 330MVT 30 32A switching Astron RS 35M 25 35A linear Astron SS 30 25 30A switching Astron SS 25 20 25A switching MFJ 4125 22 25A switching MightyLite MFJ 4225 22 25A switching MFJ 4035 MV 30 35A linear Samlex SEC 1223 23 25A sw
151. w do use a beverage antenna 3 2 10 How do l use different antennas for receive vs transmit As previously stated nearly ANY antenna can be used with the IC 746 provided it can be matched to the 746 s 50 ohm unbalanced antenna terminals However there is more to using a beverage antenna than just impedance matching Beverage antennas tend to sacrifice gain in order to improve their signal to noise ratio So while they are good for receiving they are poor for transmitting Therefore you would typically use a separate antenna for transmitting Split VFO Method While not convenient the IC 746 can be configured to use one of its antenna ports for transmitting and the other for receiving Run the rig in split mode with both VFOs on the same frequency but have VFO A use antenna and VFO B use antenna 2 External Antenna Switcher Method A more traditional approach albeit more work is to take the HF transmit signal from one of the accessory ports activate a coaxial relay via a driver transistor to switch between antennas This is the same basic setup you would use to control an external amplifier refer to articles and external amplifier questions for more information External RF Sense Antenna Preamp Method Some manufacturers make antenna preamps that sense the RF on the line to switch between antennas as well as switch in out the preamp The Ameco PT3 preamp is one example 3 2 11 How do I measure SWR while in SSB

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