GE for repeater operation
Contents
1. The response should easily make 8Hz 10 KHz Receiver ICOMs Like the transmitter side the receiver side EC ICOMs will need bias voltage to be on frequency The two main differences is the bias in on pin 2 and it will be 5 0v instead From a spare old receiver ICOM strip the parts add two jumpers and the trim pot as shown Adjust the pot for the 5v output on pin 2 SA 2 rs rat ages aj i A 4 7 a n Bl da aa Receiver The receiver is easier for flat audio For start the audio will be picked off the discriminator of U602 There are active components such as Q601 to bring the level up however complicates maintenance For example adjusting R608 would change the TLP To simplify the FM DET MTR audio is used which is from the discriminator going through a few connections then appearing on P904 3 From pin 3 there s no outside connection from this point so a jumper was installed from the IF audio board s P904 3 to the oscillator multiplier board s P903 3 old Rx F3 select line From this point it goes out the old F3 Rx line and ends up at J2 3 on the back of the chassis The Rx F3 line is not planned to be used plus there appears no components on this line to affect the audio making this an ideal circuit for audio output Optionally remove the bottom cover and shield to gain better access to the points to the jumper The stock TLP for this point was found to be too low around 25 therefore2. R607 value is changed from the 180K to 1K This brings the TLP up to a typical 16 which the external cor af board can handle this level see separate document on that device Next the receiver s cor signaling can be obtained from the stock CAS from U603 that appears on P904 9 and ends up at J1 13 on the back of the chassis Using unused lines is a cleaner way instead of the audio and cor wires running through the chassis Below is a close up of that jumper showing it from the discriminator point One nice feature over the Motorola is the little shield is not soldered to the board making removal a snap TS Sao DIDDL fi tat PEPEE ah alr bi gt y Transmitter control option The OEM drawings can cause some confusion with parts identification For example on the exciter board Q114 Q113 ID is grouped together with the slash on the schematic diagram Also on the board layout drawing the first significant digit of these parts is deleted For example Q114 becomes Q14 SRG will use the latter part identification The receiver s ICOM runs continuous but the transmitter does not causing the latter crystal aging to be longer This can be changed The Station control card on the shelf provides both continuos and keyed 10v On the exciter board the continuos 10v appears on pin 7 of P902 while the keyed 10v appears on pin 12 Continuos 10v supply inputs Q13 at its emitter Keyed 10v to R56 turns on Q13 i
3. in the RF port for tuning won t do in this case Interfacing Being the repeater is on a single frequency other F select lines may be used for other functions in this project The rear connections on the motherboard will be used for I O to external equipment involving P1 P2 and TB1201 on the rear The first two use the larger molex type pins This avoids some additional wires running around the chassis for a clean installation Flat audio For multiple links you need a flat system to sound decent This station is conventional therefore the stock circuit is not flat While the receiver is easy to set up for flat audio the transmitter is more difficult but doable because OEM design is phase modulated PM for several functions This manual will address this and will involve the COR AF board designed by AK2O covered in a separate document Stock 20 ee vain Acronym ICOM Integrated 8 D Circuit Oscillator Module The operating frequency determining element is the out quartz crystal inside the ICOM Shown here is the Tx 2C ICOM circuitry with a crystal compensator a oscillator and two frequency we Be modulators phase and co MPENSAT ION COLD END COMP O HOT END C CC 3 L OSCILATOR 49S 27 or 30 pf fiz direct The latter is used as the compensator email i EE CONNECTION MADE DURING FACTORY
4. is also referred to deviation of the carrier at an audio rate For amateur radio 100 system modulation is normally 5 KHz Other areas or services have different bandwidth standards such as 2 5 KHz For this document we will only cover the former 5 KHz deviation TLP Test Level Point refers to a measurement point on equipment in reference to TTL 0 dom is referenced to 1 milliwatt at 600 ohms Therefore a 1 dom tone into a transmitter at with a TTL of 0 dbm would fully modulate the system If the far end receiver was set up the same its output would be a 0 dom level as well Levels are stated in transmit receive Tx Rx order Therefore an audio VF drop TLP of 0 0 would mean a Tx TLP of Odom Rx TLP of Odbm Sometimes operating levels are not at TTL In this case a level would be so many dB down from TTL or just called xx down For example CTCSS sub audible tones normally are 18 dB down 1 8 deviation from voice or 18 dB down from max voice and or TTL To avoid technician confusion two sets of numbers are commonly used in diagrams and on the physical equipment s ports or I O connections Figures in parenthesis are the TLPs Non parenthesis figures are absolute actual operating levels Levels below 0 dbm are negative while above are positive Take this into consideration when working with system gains or losses Normally the negative levels have a minus in front of the number while positive have a plus sign Thi
5. motherboard etc You will need to do a lot of back and forth tracing since these lines appear on several pages of the manual The Author provided a simplified block and level set of diagrams that are supplements to this document It greatly clarifies the circuits to someone just starting out understanding this radio This material may be copied in complete form only for non profit purposes such as for the knowledge for the amateur radio service with AK2O credited as designer For other arrangements please contact the Author Copyright AK2O 2014 14
6. 5 A CG decoder signal H41 A place to control the RUS line 3 _ CG dector a 0 PL Q 10K CS 1 or valid decode 2N3904 i AA A Shown here is a convenient location to tie mount the two transistors and resisters Remember These design ideas are for a conventional repeater only For SRG flat equipment the next section applies 1 COR AF Board mount This board is an independent custom board designed by the Author for many different interface applications for SRG projects In this case it takes both the RUS and CG decoder lines to make an AND squelch either for the PTT audio or both The PTT and audio lines then will drive a downlink transmitter REMOTE aAupto REM Tx F1 control single frequency This repeater is set up for single frequency operation F1 for both transmit and receive OEM strapping is done in two separate locations and may be difficult to find without a detailed search of the drawings and their functions Both are tied low via A A is the same as ground Each jumper location is For the transmitter is located inside Tx Rx drawer unit and inside the exciter section There s a jumper on the back of J933 pin 8 to This task is to mount the cor board on a station card The line driver remote audio card was selected 19A129924G3 because several were available and the stock card would not be used in any SRG projects First remov
7. GE Mastr Il Station interfacing for repeater link use By Karl Shoemaker Introduction This document is written to include interested people in serious construction of a quality product Its rather technical however if you have a basic electronics background with some repeater building experience this should not be an issue Some of it s dry reading however you need to spend time on this to better understand advanced circuits later on Understanding schematic drawings is required If you are new at the repeater operation you might want to seek experienced help Allow plenty of time to construct each radio especially the first one No free technical support is available however some printed documents are available on an occasional bases for a modest cost for P amp H The project is designed for amateur radio not commercial and is open for discussing changes and improvements without notice Should you feel qualified you are welcome to deviate from the Author s design Images in this document may be used to illustrate a point only and may have been taken at different stages of research and development therefore may not show the end product in some cases Overview For this project the GE Mastr II station in the amateur 2 meter band is used This project is an access repeater for Spokane Repeater Group users This equipment works in the foreground for providing local coverage for the users to enjoy It s interfaced with extern
8. TEST ony fa e i i A tem perature change 6 1v AuDio RC 3I14A causes the crystal to change Figure 3 Equivalent FM ICOM Circuit in frequency such as ina mobile environment To keep it on frequency in this situation a compensation circuit consisting of two thermistors and some resistors are set up in a voltage divider arrangement with supply from pin 1 With temperature changes they switch in or out changing the voltage across a varactor diode reverse bias if you will which is paralleled across the crystal making it a direct frequency changer AKA direct FM However this is not an audio circuit in stock configuration All 5Cs and 2C have compensation built in Only the 5C s compensation voltage goes out on pin 4 ECs do not have any compensation therefore depend on compensation voltage from a 5C ICOM via its pin 4 Besides stability if there s no compensation voltage they won t net on frequency 5 7 KHz low Note the OEM drawing is a little vague to say a 2C s compensation voltage does not connect to pin 4 except during factory testing However the 5C does and this line on pin 4 is what drives the other ECs The audio input on pin 3 phase modulates the second varactor diode which is in series with the crystal and oscillator transistor Since its PM won t be good for flat audio The FM will with some modifications The FM compensation circuit also can interfere with good linear audio so should be to be removed T
9. al linking equipment for positive and full time connection with the rest of the SRG system From OEM specifications no performance or reliability degradation was observed from the modifications discussed in this document Acronyms Definitions Semantics and Theory basics To be very clear on this philosophy we will start with very basic theory Radio systems send intelligence voice data etc by modulating the originating transmitter and decoding detecting this modulation at the far end receiver back to something usable to be understood How well this is understood depends greatly on how well the system is set up Just about anyone can throw a system together to make it work somewhat Amateur radio can develop the art of radio and improving operating practices in this area This can seta good example for others including the commercial industry to what some amateur radio systems are capable of doing and to provide Public Service communications in time of need This includes the technical side to produce a high performance repeater or link A typical commercial system uses the audio portion of 300HZ 3KHz for signals This document covering system performance will be somewhat different It also calls for good technical management For one technician organization and discipline is necessary Plan on what you want to do for a system design and Stick to it Force yourself to keep good practices One good practice is to establish level refer
10. asons tone control will complicate the repeater s control however is doable The repeater PTT can be an AND squelch via the repeater control cards OR gate of CR12 and CR8 from the inputs of RUS and CG Detector voltage respectively However the conventional repeat audio will still be on carrier squelch via Q13 on the repeater audio card For a repeater with a significant long tail and having some RFI this can be rather annoying to listen until the PT T carrier line drops out the transmitter To fix this issue the repeat audio also needs to be an AND squelch Some explanation may help you in this next task The RUS is an open collector line with a pull up same as the CG decoder line The latter get s its 10K pull up from R24 on the repeater control board Therefore you can t tie the line lines coming into the board otherwise the R24 will raise the RUS line enough to keep the transmitter keyed continuously The solution is a buffer circuit from the CG line to the RUS line This allows the RUS to be 0 during standby and to a 1 during activity with the CG decoder only controlling the 0 state thus creating an AND squelch Both lines have to go high to activate the PTT circuits d Therefore a simple dual transistor buffer was installed on the System board s P935 which provided 4 spots PL o CS relaxed z OL P904 8 A power source 10v pin 1 A ground A pin
11. distribution slightly different over Motorola s Compa Station The stations power supply is a rough 15v semi regulated only to the point of the ferro resonant AC transformer The rough 15 volts is routed to two places the PA and the control shelf s 10v regulator control card That card also controls the transmitters PTT and audio The OEM says there are boards on the control shelf however the Author prefers to call them cards The Author feels calling them cards pullout devices helps identify the item to the newcomer to this radio Fix mounted ones can be called boards The receiver s boards are interfaced with what GE calls the system board not to be confused with the control shelf s back plan board that Motorola calls theirs which GE calls the motherboard The exciter control is simple Most of its circuits are hot The control card on the station shelf inputs low going PTT and outputs keyed 10v that goes to the exciter s P902 12 to key the station This makes the system amateur friendly and easy to troubleshoot Motorola s way is rather complicated for the compa The receiver is conventional with an ICOM LO mixer and front end tuned stages When bringing the unit out of commercial service you have to carefully tune its stages You may need the OEM service manual and test set to do this effectively since the receiver is very selective Just cramming a high level signal
12. e all the components except for the front pots There s about 120 components and 5 jumpers typically so this will be labor intensive The daughterboard pins in the center can be removed however in most cases this destroys the runs as well An alternative is to cut them off flush with the board The board on the left is the stock right with the components removed The pins are yet to be cut or removed in the picture below The OEM repeat audio and repeat control cards are not used in this case only the reg control card is used RO ae i wk ae Transmitter F1 jumper x i f A Vase EB T o EAEE WLIS i E H i ye k w 12 pin 4 the latter being ground It s usually a short white wire sometimes behind the blue F1 wire and may be hard to find For the receiver is located inside the Tx Rx drawer unit and on the system board A901 There s a jumper between points H47 and H48 the latter being ground right image More difficult circuitry Another circuit that s hard to trace physically wires and in the OEM manual are a couple of jumpers for the VOL SQ HI circuit Inside the drawer unit Tx Rx chassis the receiver outputs this circuit on P904 pin 11 which plugs into J904 pin 11 on the System board The System board s run takes this over to J951 pin 8 J951 is the closest jack to the chassis edge P951 pin 8 plugs into this Within the short wiring hardnes
13. ed Squelch System The term PTT Push To Talk came from a button on a radio s microphone For this documentation PTT will describe an active going low for DC functions such as transmitter keying PTT Input It also will describe a receiver s COR line driving a NPN transistor with the open collector being Receiver PTT Out or just PTT Out PTT 1 will describe this function however with a buffer such as the output of the COR AF board which changes state for user signal change of status This function would be used for audio switching such as Auto Patch audio routing PTT 2 will describe a buffered and hangtime tail output of the COR AF board to keep a repeater s transmitter keyed up AKA tail for normal back and forth conversations of the users of such system s One or both types of PT Ts may be time out controlled PLI means Private Line Indicator or Input It s also similar to a CTCSS line out of a tone decoder HUB means Hang Up Box Motorola s uses a closed loop for a HUB in mobiles and base station control AND squelch means it takes both carrier tone to activate a COR board transmitter or system AND squelch is also referred as a variable sensitivity squelch whereas the squelch setting affects activity threshold An OR squelch does not whereas it bypasses whatever squelch setting using only tone to keep it active More is discussed later in this document SRG means Spokane Repeater Group a n
14. ed on site transmitter including any IDer audio This would be a single site station with possible linking into another repeater group or service Also both the repeater control and repeater audio cards would be used on the station shelf e Flat audio 4 wire drop in station with full time link support This is the normal configuration for SRG with its receiver audio amp PTT downlinked to another station typically a distant HUB repeater or MCP with the uplink return audio amp PTT from that HUB or the MCP Therefore the 2 meter station is not stand alone the audio and carrier path goes through the distance end Only the regulator card would be used in this case Many of the OEM circuits and idea are discarded and bypassed Local monitor audio for conventional stations For SRG packages much of the audio COR PL decoder and PLI paths are custom set up ignoring most of the OEM circuits used in the station However for a conventional station not flat audio it would be helpful for you to know some points For remote site receivers you need to have three outputs e Audio to feed a conventional controller and finally the associated transmitter e COR RUS to drive the controller and or repeater control card etc e PLI CG decode output an indication there is a valid tone CTCSS on frequency to control the Station s audio and PTT circuits Obviously for receivers on carrier squelch this last item won t appl
15. ences Some call these benchmarks or baselines While old methods used linear microvolts watts etc units of measure most SRG designs and operations use logarithmic units in dom Once accustomed it s easier to see the entire picture this way when designing a system or checking system performance and keeps the guesswork out of troubleshooting a subtle level problem Most radio systems in the VHF UHF and microwave are line of site for the radio paths On the ground a path has limited range From high remote sites greatly increase this A repeater is a generic term for user s signals to be received input and retransmitted output This greatly increases radio coverage especially at high locations A link is a one way transport method for support of such a repeater For example a repeater s input receiver may need to be downlinked to a central control point such as a voter or connection to the outside world telephone internet etc From this control point the system output can be uplinked back up to a high transmitter output for the users to enjoy wide coverage of such a system In this case would be a multiple site repeater system of links etc SRG design addresses these points in detail and quality References can be expressed with a few acronyms TTL Test Tone Level is referenced to a 1 KHz audio tone to 100 modulate a transmitter in this case FM frequency modulation for an LMR system FM
16. final operating frequency For example a typical LMR VHF transmitter would be 12 times or a tripler driving another doubler driving a final doubler Fc 12 MHz x 3 x 2 x 2 144 MHz Frequency multiplication also multiples the modulation of the fundamental Since this arraignment multiples the crystal frequency 12 times it won t take much capacitance change to obtain 5 KHz modulation deviation at the operating frequency The diodes come in various specs for capacitor range Typical is 10 13 pf for LMR The radio The GE Mastr II Station is housed in chassis taking up 7 RUs 12 14 The transmitter Receiver drawer door unit is in a separate box with 3 I O connectors plus the two RF ports It duplexes just fine even with the top cover removed Note there will be some comparisons with the Motorola s micor Two types of transmitter exciters were produced the old type using a conventional crystal inside a plug in module called an ICOM The transmitter tuned stages were multipliers and amplifiers The newer type was a PLL for frequency control The voltage controlled oscillator is capable of anywhere in the design frequency band in this case 136 174 MHz It sees the ICOM s LO and locks on to it in a very short time This type requires only one tuning adjustment which is the VCO s range coil The nominal RF output is 23 dom This drives the external RF PA that has a gain of 27 db GE does their voltage
17. here are reputable people that will differ with this practice so take this into consideration for your own project Most SRG stations are located at a temperature controlled site so compensation is not a major concern especially if you add the appropriate temperature compensation capacitor to keep the crystal on frequency within the 002 PPM spec that s 0002 There were three versions EC 4 researched to modify the fe FM AF Input V ICOM for direct FM i however only version one is most successful and covered here For 5C and 2C ICOMs remove the separate little daughter board inside the ICOM To greatly improve the FM AF se TLP change out the input 3 bat j resistor from the 56K to S g e a a 1K Change out the RF j filter cap from 01uf to 100 pf to prevent top end roll NENEN ETENN ca off SRG modification version 1 amp IV PMAF Input Change input resistor to 1K For the 2C you will need to Ghange bypass sap to 100 pi reconnect the pin 4 run Change coupling cap to 22 pf Next you will need a bias source to run the EC Bias source If you have a spare transmitter ICOM EC 5C 2C etc remove the screw on top and pry open tabs on the bottom edges of the ICOM Note The screw will be either a Torx 6 or a allen hex type size of 050 about 3 64 The Torx bit or Torx driver red handle as shown in the image can be found on the Inter net as well as the 050 hex driver yellow hand
18. le Shown is the Xcelite part LN 20 050 Mouser Elect 578 LN20 The PCB has several components including the fundamental oscillator crystal modulation and compensation circuits Strip the necessary components off it to isolate pins 1 4 and 5 The Author chose to remove all components for display and research reasons Next install a 10K trim pot 10 or 20 turn type is best The holes used that line up with the pot s leads put it in a great spot for a tool to access through the top of the can when completed You also will need two jumpers on the ICOMs board pin 1 to the top of pot 10v and pin 4 to the wiper The low side of the pot goes to ground One minor twist the adjustment will be reversed CCW to increase the bias voltage We will now call this the bias ICOM Shown here is the EC ICOM in position one and the bias ICOM in eight Note the easy access hole for the bias pot adjustment The Author was concerned about the PCB pins touching the can Using a piece of laminate plastic prevents this Make a notch for the rivet area Assemble the bias ICOM can and screw and install it in any position other than the channel s ICOM which would be F1 In the picture the bias ICOM is in the F8 slot Inject a test tone to deviate the transmitter fully in the amateur world is 5 KHz Tune the bias for best symmetry You will have to reset the input test tone to verify its good at TTL Typical bias will be 3 41v
19. on profit organization for the development of equipment operation and enhancement for the benefit of other amateur radio operators for communications support especially for Public Service emergency traffic and other hobby type discussions Other definitions acronyms and other shortcuts are for practical reading and document space For example names are truncated only after the full name is established This avoids misunderstandings For example the parts list shows several manufacturers in truncated form such as Mouser Electronics a major parts supplier which may later be referred to as Mouser FM There are two ways to frequency modulate a transmitter PM and FM Phase modulation is the easiest design with good frequency stability however lacks low end audio response However PM has natural pre emphasis which works well for the LMR standard On the other hand FM has much better response flat audio at the cost of more complex engineering for frequency stability With synthesized PLL transmitters this is major consideration However later technology in design has allowed FM to perform well in LMR systems It s also referred to as direct FM With careful design changes FM can perform well and is the method used for SRG equipment A quartz crystal is normally used to control the frequency of an oscillator A capacitor across the crystal can fine adjust the frequency in the form of warping it Transistors and diode
20. s a white wire takes this to J932 pin 16 P7 plugs into J932 P7 pin 16 has a little bare jumper DA on the outside going to its pin 17 left image This goes back inside to J932 on pin 17 now A white wire takes this to the top of the squelch adjustment pot located in the chassis of the drawer unit There is also a short yellow jumper called DA from J932 pin 17 to 3 for other functions right image Wow what a wild circuit P7 DA jumper J932 DA jumper 13 Below is the schematic locations from the OEM manual for the Rx F1 jumper the VOL SQ HI jumper DA and the discriminator jumper to be added 19041721361 CG DET OUT gt ASO RECEIVER TX CG DISABLE gt CGHI SYSTEM BOARD EXCITER bie Ei l 903 P903 RX OSC MULT SPKR HI gt ee ae iai 19041726261 qa nx re SPKRLO gt i N lt Ix F4 wa VOTING Inx Fs Tx olsgact gt Ipx F6 IRx F7 gt I6 Rx F8 gt I7 la cas gt jiov sys SPARE gt I9 gt RX OSC CONTROL SPARE MULT MULT 2 19041721361 A90I SYSTEM BOARD 903 P903 RX OSC MULT gt OPR mops aja k F5 lax f6 co lrx FT L hov sys l irx osc contRoL E spare e muir sa MULT 2 S9821976IP3 BLKA DISABLE J904 RX FAS __ la MULT 2 Tra ae i zE a DISABLE The OEM manual shows most of the connection lines between various components of the station such as the system board
21. s have a P N junction inside the case The junction has a space in the middle in the form of capacitance called the depletion zone By applying reverse voltage will affect the zone More reverse voltage results in more space causing less capacitance In a RF circuit this can mean higher frequency in general Applying audio intelligence will cause the frequency to change at the same rate Special diodes are made for this purpose called a varactor diode vari cap There s a range the diode will work in causing a linear frequency change from the voltage change on the diode A bias DC voltage is normally applied across it to stay in this range The audio rides on top of this bias Careful design is necessary to create good symmetry waveform on a frequency modulated RF carrier This is practiced for SRG projects Most PM transmitters have the diode in series with the crystal causing a phase difference from the fundament frequency while most FM transmitters have the diode in parallel to the crystal with the anode to common ground Modulation and Deviation are the same results when talking about FM Deviation of 5 KHz means 5 KHz above the center frequency and 5 KHz below the center frequency making a total bandwidth of 10 KHz There is other energy in the form of sideboards which won t be covered in this document The fundamental crystal frequency will be converted by multiplying its frequency to obtain the
22. s is also true for absolute levels as opposed to TTLs For example most transmitters run a 42 dom while most receivers sensitivity run a 117 dom for 20 dB quieting These levels are at the transmit and receiver ports respectively Also known as TOR Top Of Radio or Top of Rack is before the transmission line and antenna outside on the tower The latter parts can be figured in for the entire system s losses or gains Single digit numbers of 1 and 0 in parenthesis or brackets are not to be confused with TLPs In this case these 1s and Os identify the logic state of a gate or other TTL CMOS I O driver circuit and so forth Another aid to avoid confusion between logic states and a TLP is that the latter normally would have a or before the number For example a TLP of 14 8 is the audio input controlled by a logic gate of 1 being a normal logic high One last word on the logic state The parenthesis indicates a state in normal standby no activity condition As a side note I TL mentioned above has nothing to do with TTL logic a type of IC series Most TIMM s and AC voltmeter scales are in dom When measuring across a Circuit you may need to have the meter in bridge mode being high impedance as not to load down what you are measuring In such cases a more accurate term of level would be dBu Having said this dom reading in bridge mode is still understood for a specific absolute level measuremen
23. t using the dom term The term COR came from the old tube days of Carrier Operated Relay whereas a tube receiver had a point when its squelch opened a tube switch valve drew current through a relay s coil to give some contact closure to key the associated repeater s transmitter As the solid state technology came in the later 1960 s the term stayed with repeater operation even though the Author saw no relay in most modern repeaters and felt the relay term should have been replaced with the term of squelch since it s the receiver s squelch that does the signaling This would be called COS meaning a Carrier Operated Squelch Both terms are correct and this gets down to semantics or content of a discussion After careful consideration of modern technology used in the LMR field by amateurs and professional alike including recent repeater product terminology and to the fact that repeater stations in the early years were also called Relays whereas the station would relay a signal rather than repeat a signal the Author decided to stay with the majority s term of COR to avoid reader confusion Therefore this and other SRG documentation will reflect this decision COS may also be used to describe a Carrier Squelch as a part of a receiver CS will be reserved to describe Carrier Squelch as a receiver s mode of operation verses TS PL or CTCSS to describe a Tone Squelch Private Line or Continuous Tone Cod
24. ts collector goes low and turns on Q14 Q14 s collector is the switched output which goes to a 5v regular and also filter divider R54 C55 and R59 This goes to the Tx ICOM s pin 2 activating RF out on the same pin and paralleled to the RF filter FL101 then to the multiplier stages To make the transmitter s ICOM run continuously lift one side of R54 lead towards ICOM pins and install a common diode in series with its anode on pin 1 of Y4 The diode lowers the supply on pin 1 close to what the OEM circuit did 9 6v Q13 and the 5v regulator will be isolated from this and still function as a keyed circuit allowing normal transmitter control while keeping the ICOM live all the time The Author choose not to do this option as of 2014 9 97 Pe fs 94 3 92 94 XY 104 wee 3 97 6 Ps Pa TE os 3 07 Ve fs 4 3 92 91 xy 106 9 Q 5 Oc 4 93 Oo on xY107 By On O n XY108 R153 R154 T tee z fe fs 94 3 Qa Quios Risa 3 x TRANSMIT SWITCH Q114 0113 gt 4 F NIDAN S ae AA NE Ya tate DN ton g ey WY Ot pe E a E AR ee aeai a Ca Bait EM RE E HOSS S sabe Bae ay a fe oh bil a Bid ayip WENE as a ines Receiver signaling options There are two thoughts to the process e Conventional stand alone repeater with linking This would be the configuration most amateur repeaters are set up with its receiver audio amp PTT going into a on site repeater controller and it s output going to the associat
25. y The main point is for a simple way the on site technician can hear the receiver s local audio Speaker for checking interference and or dynamic sensitivity checks while not affecting the normal station s operation i e keying the station s transmitter to check for receiver desense Kee AT Kie For stations that don t use the repeater the local speaker control card take out the jumper H41 i H42 This prevents the CG output signal from providing a low at the receiver s P904 7 line which controls U603 and U604 there For stations that do use the repeater control card the above cut won t work This is because the PLI CG output goes into the control card on pin A3 This signal goes back out of the control card on A6 to mute the receivers COR and local audio The best place to change this was found to make a cut on the run from J904 7 and H42 The run cuts are then tinned in this image for easy identification only This prevents any CG signal from muting the local speaker Therefore the local speaker will always be on carrier squelch This also prevents the local or remote PTT switches or the regulator card H18 area from muting the local speaker audio as well However there still is another issue which is addressed on the next page 10 RUS Repeat audio AND Squelch In times of carrier squelch operation no interference is simple to operate a repeater In times of interference or other re
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