KB2LJJ Radio Mods Database
Contents
1. verify with ohm meter Dress the cable connected to ACC 4 pin 5 over to IC8 pin 9 Cut to size and solder be careful use minimum heat and thin solder The exposed shield is discarded and heat shrink tubing placed over the end to prevent any shorts that would otherwise occur from having exposed strands of the shield touching something Dress the other cable connected to pin 3 of ACC 4 to J31 and cut to size Prepare the end in the same manner as the other cable Solder the center conductor to pin 2 of J31 This is accomplished by cutting the lead going to pin 2 about 1 2 inch back stripping the insulation back 1 8 inch on the two ends and then joining the center conductor of the cable going to pin 3 of ACC 4 and soldering the three exposed ends together Use heat shrink tubing to cover the solder joint NOTE that the banded end of D81 is not the cathode of the varactor diode There is no need to insert any additional capacitance in series with J31 pin 2 The shields are not connected at both ends of the RG 174 cables in order to prevent ground loops The Aluminum heat sink was used as ground as no other ground was available that was close to ACC 4 Your sight may be better than mind and you may find one Adjust VR 1 on the MC NB96 board for 75 mv p p as measured on pin 2 of J31 This will give a good initial setting for injected transmit audio level This completes the modification 9600 BPS Packet can now be enjoyed on each of the bands in2. This mod should have no affect on 1296 as it is rated the same on SSB and FM I will do a two tone test just to make sure it is still clean Subject Pictures http www kb2ljj com data kenwood ts 790 htm 12 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database Ale BOARD SPAN DOWN JUNIPER IF UNIT X48 3050 00 sw d X41 3050 00 Gi He yr L DI gs optional voice ynthesizer VS2 N ower down P m n http www kb2ljj com data kenwood ts 790 htm 13 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database TS 790 A E 9600bd via ACC4 port RX problem Author Hans PA3HGT A few owners of a Kenwood TS790A E have some complains to receive weak packetsignals at 9600baud speed with a packetradiocontroller of Symek model TNC2H DK9SJ if you operate 9600 bd packet with the ACC4 port check this e If you connect the tnc packetradiocontroller of Symek model TNC2H DK9SJ with the ACC 4 port you can hear a slightly different sound then when the tnc isn t connect to the ACC 4 port of your TS790 A E e Signals with a strenght 3 and above are no problem but below strenght 3 is diffucult to work with 9k6 packet The problily cause is that the input of the amplifier in the TNC has an too low impedance for the Kenwood TS790 A E if osc section The simple solution is to solder a 100 K 1 4 wt resistor in the RX audioline between the TS790 A E acc 4 port pin 3 and the 5 pol din of the TNC from Symek pin 4 I start
3. about 10 Watt less than the FM power The reason for this is unknown to me especialy because a transceiver gets less hot in SSB mode There is a simpel mod to get the same outputt power on SSB 45 Watt Trie to work ESD anti static safe and if something goes wrong don t blame me Near the ALC board is a jumper that looks like a diode but in fact is just a 0 ohm resistor You can find the alc board when you remove the outside covers and putt the transceiver upside down look left front You will find the SSB power down as shown in the picture Just reconnect it and You will have 10 Watt more PEP power on SSB Suggestions comments ideas just mail me PE3HMP Hotmail com om data kenwood ts 790 htm 19 di 19 01 09 2009 0 13 16
4. band mode diode D32 on the control board must be opened In addition two resistors must be soldered to a 13 pin din plug which will be connected to the ACC 2 jack on the back panel of the transceiver To locate and open D32 Disconnect the power supply and antenna from the radio Remove the 14 screws that secure the top and bottom covers Carefully remove the top and bottom covers Locate the control board this is a vertically mounehind the front panel Locate diode d32 towards the top right side of the board Using a small pair of wire cutters cut the lead of the diode do not pull on the lead or the diode as this may tear the foil on the other side of the board assemble the radio by reversing steps 1 3 13 pin DIN plug configuration Using a small flat blade screwdriver lift up on the tab of the nylon cover Once the tab clears the slot of the metal holder pull the cover off the plug Carefully separate the two metal holders and remove the pin assembly First tin pins 1 8 and 11 of the assembly so the resistors can easily be soldered in place http www kb2ljj com data kenwood ts 790 htm 6 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database SOLDER A 100K ohm 1 4 watt resistor between pins be cut and shaped before soldering Solder a 1 5K ohm 1 4 watt resistor between pin 8 and the lead of the 100K ohm resistor that is attached to pin 11 the resistor leads should be cut and shaped befo
5. his TNC s DCD LED stays steady no flicker UO 14 RX freguency tracking for TS 790 FT 736 The doppler shift range in overhead pass reaches to 20kHz It is essential to tune in RX frequency for good through put I assembled auto freq tracking for UO 14 FSK signal reception and achieved good result Block diagram RX discri out lt voltage comparater INV NOR switching TR gt Down control 01 02 02 03 G3RUH board DCD Circuit connection table GND Q1 LM324 or TL084 02 74HC02 03 25C945 etc 20 01 a R 1M 3 OL I1 6 Q2 4 3 02 1 R 470 BE QS Q DWN 12V R 8k 2 2 k gt VR GN GND b lt G3RUH board DCD line to RX discri out G3RUH board RX IN to G3RUH board DCD line U10 pin 13 to down control pin of mic terminal TS 790 mic pin 3 http www kb2ljj com data kenwood ts 790 htm 5 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database setting of VR 10k The discriminator IC output level is 5 8V 2V Without RX signal set the VR to Q1 pin 1 level turn HIGH gt LOW In my case I assembled the circuit on a small universal PCB and enclosed into TINY 2 with NB96 board In the case of FT 736 DL signal polarity is different from TS 790 so change as follow gt gt DL signal to mic terminal Diode 151588 etc TS 790 cross band repeater mod To operate the TS790A in the repeater cross
6. of R15 204 located the left of Q5 they are located roughly oposite side of L2 L3 gt JAG6FTL says the modification needs a magnifying glass Hi http www kb2ljj com data kenwood ts 790 htm 8 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database There is Reply Here is additional info to the modification Need magnifying glass I am not farsighted nor shortsighted Hi This modification is to disable the blocking line for IF amp Audio muting function remains unchanged but it is no problem to use rear data port Audio muting circuit consists of D20 and 912 Put the frontside toward you and remove the bottom cover of 790 2 Remove the 13 screws that fix IF board Lift over up the board toward you Q5 and Q4 are located just opposite side of L2 and L3 Chip Q5 printed V11 has 4 solderd legs and it s located next to R15 470 ohm surface mount resistor printed as 471 04 is located just beside R15 and has 3 legs TS790E Burned out diode Hi to all fellow TS 790E owners Just a quick note to warn users of this magnificent wireless of the dangers of exceeding the recommended duty cycle on full power transmit on 430MHz My 790 puts out about 45 watts of RF on UHF slightly more than the quoted spec The other night whilst listing messages from the BBS I suddenly lost RF output from the UHF section The radio was also drawing excessive current when the TX was keyed 22 Amps 13 8V normally 16 Amps full output p
7. selectable FM filters FM narrow and wide F and G type but using the 4 element version CFU I have tested both Icoms extensively on the FM narrow wide effects and found the following 1 Lowering interference despite the low stopband specs the better selectivity of the narow 9Khz filter do help avoiding next channel interference 2 Better sensitivity smaller BW creates better S N ratio at weak signal levels 3 Restricted IF BW results in slightly less audio bandwidth How much usable evidence did I find during the above tests 1 QSO was possible yes no In most occasions the next channel 12 5Khz interference completely dissappeared Rigs having no filter choice and having the E version filter older or i e IC821 IC271 as such suffer more from interference 2 QSO was possible yes no 3 I m not into Hifi But the narrow BW does have a negative side effect stations which are overmodulating more swing will appear outside the filter causing audible drop outs Next if you require wider BW for 9K6 packet use etc the 20 or even 30Khz filters are to be preferred See also the mods info on several websites 73 Mark PASMW TS 790 mods for This short note is addressed to Paul DUIPOL originaly but it may be help of them who has the same problem I uploaded addressed To All here Hello Paul G3RUH 9 6kbps modem connection need mod to both TX and RX of 790 IC8 MC3357P for m
8. the ALC unit on the IF pc board The IF pc board is located below the Kenwood TS790 So you have to remove the bottomcover You can see on the picture of the IF pc board how to locate the ALC pc board X59 3480 00 The picture with the ALC board shows how to solder the capacitor Be careful to solder with not too high temperature because you can damage SMD components You can choose to solder de capacitor between R201 or D201 and GND if you don t like to solder on pin 6 of IC201 see picture ALC pc board Work if possible ESD Electro Static Discharge safe Succes I take no responsebility if things go wrong 73 Hans PA3HGT Pictures are taken from the servicedoc ts790 of Kenwood aman d wh a Bab 8 Beo vel Gras Qs cm BE aa r e 1 aver Ben da yo MICRA 34 9 56 1 vena vas s ver oll EI 24 a AUC PC BOARD x58 Say http www kb2ljj com data kenwood ts 790 htm 15 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database Convert TS790E to the USA TS790K and RX TX mod Author PE3HMP PE3HMP hotmail com My idea was to disable the 1750Hz feature on the TS790E and enable the sub tone encoder Kenwood USA was not willing to help because I m outside the usa and Kenwood Belgium says it can not be done Before You even open the tranceiver try to work ESD anti static safe use a wristband connected to a clean earth make sure Your soldering iron is connected to the
9. 40 905 1230 1305 140 168 425 458 1240 1305 General aarket 144 148 430 450 1240 1300 144 148 430 450 1240 1300 RX only 140 168 340 373 425 458 B40 905 1230 1305 144 148 430 450 1240 1300 RA IK 140 168 340 373 425 458 840 905 1230 1305 140 168 425 458 1240 1305 General market 144 148 430 440 1240 1300 430 440 1240 1300 RX only 140 168 340 373 425 458 840 905 1230 1305 430 440 1240 1300 RXZ TI 140 168 340 373 425 458 840 905 1230 1305 425 458 1240 1305 European 144 145 430 440 1240 1300 144 146 430 440 1240 1300 140 168 340 373 425 458 840 905 1230 1305 144 146 430 440 1240 1300 140 168 340 373 425 458 840 905 1230 1305 140 168 425 458 1240 1305 144 146 432 438 1240 1300 144 146 432 438 1240 1300 RX only IO M 140 168 340 373 425 458 840 905 1230 1305 144 146 432 438 1240 1300 140 158 340 373 425 458 840 905 1230 1305 140 168 425 458 1240 1305 144 146 130 440 1240 1300 144 146 430 440 1240 1300 140 168 340 373 4 58 840 805 1230 1305 144 146 430 440 1240 1300 140 168 o P 140 168 425 458 12 1200 1305Mliz D21 1750Hz when present enable sub tones when not present D29 Wide RX if not present D30 Wide TX if not present D32 Cross band repeater if not present http www kb2ljj com data kenwood ts 790 htm 17 di 19 01 09 2009 0 13 16 KB2L
10. JJ Radio Mods Database Well to change the European version to the K version you have to cut the following diodes do it so that it is possible to reconnect them You never know if you want to return it to it s original state Cut D21 You have to remove the entire control unit because its on the back of the control unit be careful with the flat cables and remove the iron clip that is holding the left ic on its place I cut the copper line on the cathode side of d21 Cut D30 29 24 23 21 I have cut them about 5 mm away from the glass Now place a 1N4148 into the D22 place You do not have to stick it all thru just make sure it makes good contact it has the same polarity as the other previously cut diodes If You want wide RX cut D29 If You want wide TX cut D30 Well putt everything back together the only thing I had to change are the freq steps to 12 5KHz and the repeater shift 0 6 and 1 6KHz Now I can work repeaters with a sub tone Like Rotterdam and Antwerp I like to thank PA3HGT and PA3DSC for giving me the schematics because my service manual was held up in the mail Well all the pictures should make things very easy for You If there are any problems or suggestions pse e mail me PE3HMP hotmail com TS790 SSB Power Up http www kb2ljj com data kenwood ts 790 htm 18 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Author Mark PE3HMP PE3HMP Hotmail com You may have noticed that the SSB power of Your Kenwood TS790 is
11. KB2LJJ Radio Mods Database EF KB2LJJ La Radio Mods Database Radio Mods Database and Manualsg i In ee col SS ll ll E ja OL x Te oii Wi m rrry 323 000 250 Ct Modifications for the Kenwood TS 790 TS 790 mods for GGRUH TAPR PSK TS 790A for use with the paccomm MC NB96 G3RUH IZSCCV TS 790 amp 9600 Baud Operation Rev 2 UO 14 RX freguency tracking for TS 790 FT 736 TS 790 cross band repeater mod TS 790 with serial freguency control TS790E Burned out diode 800MHz Receive Mod for Kenwood TS 790 TS 790 SSB Power Increase TS 790 A E 9600bd via ACC4 port RX problem Kenwood TS790 ALC modification Convert TS790E to the USA TS790K and RX TX mod TS790 SSB Power Up FM 455Khz ceramic filter choice In todays FM transceivers you will find either the CFU 4 element or the CFW 6 element type 455Khz ceramic filter for FM The CFU is mechanical smaller The CFW which is used in the TS790 has better freguency characteristics The choice of filter type depends on what bandwidth you prefer Some commonly used sub versions Type BW CFx455B 30 Khz CFx455C 25 Khz CFx455D 20 Khz http www kb2ljj com data kenwood ts 790 htm 1 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database CFx455E 15 Khz CFx455F 12 Khz CFx455G 9 Khz The TS790 uses a CFW455F in each IF strip for FM Competition like Icom 746 and 910 use two
12. ain RX IC1 MC3357P for sub RX pin 9 is the point to draw RX signal Usualy sub RX is used for satellite communication as TX RX freq is different But I drew both main and sub signal and switch them with a microrelay This relay can be controled with main panel SW 144ATT see 790 manual These mods are essential for G3RUH 9 6kbps but also usable for FO 20 PSK BUT with my experience there is many trouble to use this mods for TAPR PSK modem TX audio level setting RX noise MC3357P pin 9 has 455khz wave element and so on http www kb2ljj com data kenwood ts 790 htm 2 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database So I use ACC2 for TAPR PSK modem also usable for 1200AFSK ACC2 connection 4 GND 9 PTT 11 TXD audio signal in 1 3 3k 3 3 3k connect together to RX audio two small 1 8w 3 3k regitor mixes main and sub audio so it is able to use for cross band full duplex and mono band half duplex operation These registor can be mounted in ACC2 13 pin plug UP DWN control from TAPR PSK modem to 790 U12 and JP5 6 setting U12 790 mic terminal pin 8 UP pin 4 pins E DWN pin 3 G GND line pin 6 and pin 7 must be jumpered and connect to ground e R75 2 7kohm may be changed to 300 500ohm for steady photo couple e C32 C34 10uF must be changed to 3 3uF or 4 7uF for rapid doppler shift tracking e R7 in TX audio output circuit must be changed to 2 2Kohm as the original have
13. ed with 10 K and ended with 100 K for the best result You hear no different sound when connect or remove the cable Symek TNC2H Kenwood TS790A E after the change No re adjustments needed Kenwood TS790 ALC modification Author Kenwood and Hans Extracts from KENWOOD Service Technical Report No E51 89 002 date FEB 10 1989 The talk power of the TS 790 is lower than previous models i e TR 851 and TS 811 Not all versions of the RIG suffer from this problem I have the TS 790A and the following modification was done when I purchased the RIG The report was sent to the following TRIO KENWOOD offices T K CANADA T K AUSTRALIA NV SA The following is quoted from the Service Report To boost the talk power of the TS 790 to almost the same level of the former models surpress the ALC response like the former models Connect a 0 039 to 0 047 uF between pins 6 and GND of IC201 on the ALC amplifier daughter unit X59 3480 00 F NOTE This above alteration distorts the SSB transmission signal quality Thus the alteration will not be applied to mass production End of quote The mode was done on my RIG from the factory and I have had no reports of poor audio The following white noise check is shown in the Service Report http www kb2ljj com data kenwood ts 790 htm 14 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database ORGINAL ALTERED Low ALC level l to 1 5 W 2 5 to 3 0 W NOTE PA3HGT You can find
14. heavy phase distortion With this change TX audio connection to mic or ACC2 is no problem no need dirct varactor feeding Mods to audio drop problem in 790 computer control In computer control from rear ACCI terminal freguency setting command makes 10m sec of audio drop mute and data collapse occur in PACKET operation This problem is fixed by killing the blanking pulse to IF amp circuit remove Q4 2SC2712 on IF unit and short the collector circuit to GND R15 470 ohm This mods is essential for auto freq control with KCT Tuner for low orbit Packet satellite This is all of my mods to 790 G3RUH TAPR PSK modem Best regards Sueo Asato JA6FTL http www kb2ljj com data kenwood ts 790 htm 3 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database TS 790A for use with the paccomm MC NB96 G3RUH The Kenwood TS 790A makes a wonderful 9600 BPS Packet Radio Transceiver as it has an excellent front end powerful transmitter and 144 440 and 1 2 GHZ coverage The CFW 455F filter inside is not too narrow despite what you may have read and coupled with the low noise front end of the rig enables the G3RUH modem to reliably decode valid data that barely moves the S meter The modification discribed below is simple reversible and does not impair normal operation or the appearance of the transceiver This isa no holes modification as it allows the G3RUH modem to be connected to ACC 4 jack on the rear panel Place the TS 790A upside dow
15. n on a soft clean surface so as not to mar the cabinet Remove the bottom cover to expose the IF Board With the front panel facing you the work area is the upper left quarter of the IF board Identify pin 9 of IC8 MC3357P There are two of these chips on the IF board but only the main demodulator IC is in the work area RX audio to the modem will be derived from this point Next locate J31 a two pin connector near D81 and X2 10 965 OSC TX audio from the modem will be supplied to the hot lead on J31 Note the large aluminum heat sink that spans across the IF board near the rear of the chassis A round lug will be mounted on it near the rear of ACC 4 jack Wire an eight pin din plug Use shielded cable for TX and RX audio No traces on the IF board need to be cut Pins 3 and 5 of ACC 4 are not connected to anything as the radio comes from the factory Make sure the Din plug fits the jack properly before wiring it PIN ground PIN TX audio from G3RUH PIN RX audio to G3RUH PIN PTT Prepare two six inch lenghts of RG 174 Prepare one end of each cable so that the shield will reach the ground lug mounted on the large aluminum heat sink The cables will be routed over the top of the heat sink and will not be crushed when the bottom cover is reinstalled as there is adequate clearance Solder the center conductor of one cable to pin 3 on the rear of ACC 4 verify with ohm meter Solder the center conductor of the other cable to pin 5 on the rear of
16. ought by WBOKSL expressing TS 790 has audio drops at the frequency change command in it s serial control JAGFTL confirmed the data loss at the product detecter on his scope too These are as terrible as if we use KCT Tuner in it s serial control option Kenwood replied to my inquiry It is made as so to prevent the noise of PLL about 100m sec mute is created Kenwood suggests the modification as below but it should be made on user s responsibility This should be solved in their next products I strongly told them JAGFTL and I confirmed that it now works perfectly on FO 20 s actual test and uSATs too with the following modification Kenwood suggestion Refer to IF DIAGRAM You could disable the mute function by following methods both or item 2 only 1 Delete D20 or R191 for SUB audio As far as you would use the rear data port ACC2 it s NOT necessary to do this although you would still have the audio drop at the sound of loud speaker Of cource you should do this modification when you would hook up the audio data from Microphone Plug 2 Put a jumper between Q4 collector and emitter for SUB RF Block This modification is a MUST You can do this by several ways but the above is most easy The following discussion might help you a bit partly eddited by me I wrote to WOFMW Cut the line between Q4 Collector and R15 470 orhm and Ground the end of gt R15 JAGFTL made the mod removing Q4 entirelly and grounding the end
17. ower I returned it the following day to the dealer where I bought it 22 months ago and they diagnosed a burnt out RX TX switching diode D2 in the circuit diagram It was not only burnt out it had disappeared It is a special component and cost about 15 total repair cost 50 One week later I got it back and all was well again with no other damage apparent I do not think the failure was caused by using packet as the duty cycle at the time was very low indeed just listing the new messages for the day I think it all started the night before when I had an hour long QSO using full power FM on 433 550 The radio gets pretty hot under these conditions and its internal cooling fan was running continuously after about 5 mins on air The manual does warn the user to allow the transmitter to cool after extended transmitting but is not specific about the duty cycle when using full power So please be careful with your 790 and don t cook it like I did It is NOT CAPABLE OF A 100 DUTY CYCLE when using maximum power on UHF It does not get as hot when using VHF but caution should be exercised if the fan is running continuously I would not expect there to be any problems when using SSB on either band nor would I expect normal packet data use to cause problems 800MHz Recieve Mod for Kenwood TS 790 http www kb2ljj com data kenwood ts 790 htm 9 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database Author Schreiter Keith keith schreiter sbt
18. re soldering Wrap a small piece of electrical tape around the resistors This will insulate them from the metal holder after the plug is assembled Mount the pin assembly in the two metal holders Slide the cover over the plug until the tab engages in the slot The U shaped strain relief will not be used Plug the 13 pin din plug in the ACC2 jack on the back panel of the radio Operating procedures The repeater cross band operation allows the TS790A to receive on one bag signals will automatically be switched to the sub band The TS790A will then re transmit the signals from the main band Each band may contain offset and sub audible tone information an optional TSU 5 must be installed in EACH BAND for decode Press the MAIN function swich to select the MAIN band Select the first operating frequency and mode fm only Select the offset as required If the CH Q is on press the CH Q switch to turn the function off Select the sub audible tone as required Transfer the contents of the MAIN band to the SUB band Select the second operating frequency anf mode FM ONLY and turn the CH Q off Select the offset and sub audible tone as required Adjustd point The TS790A will transmit in the repeater crossband mode if the squelch controls are set too low or a signal is received Adjust the power control to allow normal output power from the MAIN band Adjust the sub band volume control to a normal li
19. same clean earth EVERYTHING YOU DO IS AT YOUR OWN RISK After looking at the diode chart of the control unit I saw that one diode is only used in the E European version so I thought it would be easy to convert it the biggest trouble was to find the D21 diode I was on the back of the control unit after removing the diode it was possible to switch sub tones on and off BUT there was no way I could set the freq of the sub tones the micro processor still saw the TS790 as an E version So there is no way to get that working properly unless You change it to version I don t know if the J M M2 W2 W3 have the sub tone feature In the Netherlands You may have a tranceiver that works outside the ham bands so converting is no problem here is what I found out that some of the diodes do 1f someone has more info I would like to know it http www kb21jj com data kenwood ts 790 htm 16 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database Destination diodes on the Destination CONTROL UNIT Receive operation Transait operation D 14448 430082 1200192 144012 430NHz 1200992 144 146 430 440 1260 1300 144 146 430 440 1260 1300 140 168 340 373 425 458 840 905 1230 1305 144 146 430 440 1260 1300 140 168 340 373 425 458 840 905 1239 1305 140 168 425 458 1240 1305 430 450 1240 1300 144 148 430 450 1240 1300 340 373 425 458 840 905 1230 1305 144 148 430 450 1240 1300 340 373 425 458 8
20. siemens com Cut D29 on the control unit Install a BNC connector on the rear panel where the black plastic plug is Run a piece of 50 ohm coax from the BNC to TP201 202 on the RF unit TP 201 is the center and 202 is the shield That is the 800 MHz rx antenna Subject Photos http www kb2ljj com data kenwood ts 790 htm 10 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database http www kb2ljj com data kenwood ts 790 htm 11 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database 8331 D29 is located on the controlunit gire controlunit is located behind the front panel of the 790 TS 790 SSB Power Increase Author Greg ki6ko innercite com If you look at the specs on your new TS 790 you will notice that the SSB power output is about 10W lower than FM or CW This is an easy fix On the IF board on the bottom of the radio near the MIC RF POWER knobs there is a small jumper diode labeled SSB PWR DOWN It is cut from the factory Reconnect it On the schematic it is shown as a jumper but it looks like a diode There was enough metal left on the leads on mine to reconnect it The PEP power will now be the same as FM CW The PA for both 432 and 2m on this radio are rated at 60W so it shouldn t be a problem I havn t tried to raise the power up to SOW yet as my Commander likes about 45W if it is carefully tuned for around 1100W out With these PA s 50W should be quite safe on both bands
21. stalled in your TS 790A For non packet operation either unplug the modem from ACC 4 or turn off power to the modem For 9600 packet operation unplug the mic and turn the mic gain to minimum Thanks to Frank Anderson W7ZTA and Jeff Angus WA6FWI for their help Please report any errors or suggestions to Mike Hooper KF6PU WB6YMH SOCA http www kb2ljj com data kenwood ts 790 htm 4 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database TS 790 amp 9600 Baud Operation Rev 2 These notes were partly taken from James Miller G3RUH notification for FT736R and the article of my good friend Sueo Asato JAGFTL These mods are working very well with 9600 bps UO 14 and CBBS operation currently used at my site Please refer to G3RUH s notification for FT736R for more detail RX TX mod suitablity remains same as his notes TS 790 FM Direct from Discriminator Detected and amplified buffered FM direct from the receiver discriminator is available from Pin 9 IC1 Sub or IC8 Main I use Sub for reception TS 790 Direct varactor FM Modulation Inject your TX audio at the cathode side of diode D81 with a 1K ohm register in series You can find D81 near Q73 in your IF UNIT diagram Misc It takes a bit hard work for very small and jungle PCB Use tiny tools Carefully adjust the TX audio level by VRI of the modem it s rather low You would probablly need some local friend to do this adjustment asking him to tell you
22. stening level to monitor incoming signals To place the radio in the repeater cross band mode press the F switch and then press the M IN switch An asterisk will light in the MAIN band display for confirmation To cancel the operation repeat step 11 and disconnect the DIN plug http www kb2ljj com data kenwood ts 790 htm 7 di 19 01 09 2009 0 13 16 KB2LJJ Radio Mods Database 13 If the DIN plug is left in place after use bleedover from the SUB band audio if present will be mixed with any transmitted audio This will make your audio during TSU 5 TONE UNIT When the TSU 5 tone units are not installed only the tone encode function can be used If CTCSS is to be used it must be installed in both bands to function with the cross band repeater mode TX audio adjustment The audio gain can be adjusted by variable resistor VR36 on the IF unit If the range of VR36 does not suffice for normal transmit audio the values of the resistors on the 13 pin din plug can be changed As an example if the audio is too low reduce the value of the 100K ohm resistor and increase the value of the 1 5K ohm resistor To access VR36 1 Remove the bottom cover of the radio to expose the IF unit 2 locate VR36 3 Use a plastic alignment tool to adjust VR36 for the bottom cover TS 790 with serial frequency control by Kohjin Yamada JRIEDE This note is the summary of our discussion made among W9FMW JA6FTL and myself The first report has been br
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