A Conversion of a high band MICOR Intermittent Station to a Repeater
Contents
1. TITUS ahkakikakik Aie ms et mmm S mee OY mae O ae S CP SD a Ea eee Micor Unified Chassis Base Station Conversion to A Ham Band Repeater by Lawrence Glaister VE7IT November 2002 Goals To duplex a base station radio set for repeater usage To mount and tune a micor mobile rx preamp for use with the repeater To locate signals on backplane for feeding to an RLC4 repeater controller To use standard micor PL encode and decode boards To complete the conversion without having access to a service manual Lets Get Started The first step is to open up the radio and remove all the mouse droppings and attempt to clean up the mouse pea Those critters love the warm dark spaces of a repeater The second step is to review the board and module numbers to determine what frequency split the various components are designed for In this modification I was lucky enough to scrounge up ham band split parts for most of the components Do not get too depressed if you can t find the ham band split they are quite rare With some work most of the parts can be modified to ham band split See the references for information on using the higher split boards Board ID s in System Transmitter components modules TLD5321A exciter board TLNS5S731APR tx PL encoder board with KLN6210A reed 100hz PL KXN1019B channel element with xtal for T147 280 xtal gt 12 27333mhz 12 Note when I received a crystals for this element they would not t2. 6 to J2 14 This enables local audio so no line driver card or squelch gate card are needed This takes preamp audio and sticks it into the audio amp for local audio x J201 removed JU 204 removed TRN6O06A Audio squelch es ea i C1399 Q Steps 4 11 convert the station version of the audio squelch board TRN 6006A to be more useful for ham controller use See reference 5 for detailed instructions The meat of the conversion is replicated here 4 Set up for AND squelch On audio squelch board cut jumper wire JU 204 between IC 202 pin 8 and P 201 pin 3 Nothing will be connected to IC 202 pin 8 5 Cut J201 on the audio squelch board to allow the PL board to filter out the PL tones in the local audio Depending on which audio source you use to connect to the controller the PL filter may or may not be active 6 Cut circuit trace leading from IC 202 pin 6 somewhere between the IC and the edge of the board component side of board disconnect squelch gate from backplane 7 Connect a 100 k to 120 k ohm resistor from IC 202 pin 6 to ground at a convenient location provide audio termination for squelch gate 8 Pin 10 of IC202 has a COS signal available but it is not capable of driving the RLC 4 controller directly Add a 2n3904 or 2n2222a as a buffer stage Between IC202 and the edge connector there is a large grounded area see photo above The emitter lead goes to ground the base lead connects to pin 10 of IC202 th
3. acement for the jumper This is especially handy for those who on occasion determine it necessary to remove the PL encoder board for any reason In place of the jumper on the exciter board install a silicon diode like a 1N914 or 1N4148 being sure of its polarity With the diode installed it will make no matter if the PL encoder board is installed or not The banded end of the diode will go toward P902 pin 8 The easiest place to install the diode is on the solder side of the card J5 19 to J5 20 Tx F1 enables pae hi 3 Supply the transmit exciter element with a ground to enable it at all times Connect pin J5 19 to pin J5 20 on the top of the backplane Pin 19 is F1 channel element select and pin 20 is ground Plug the channel element into the F1 position closest to the pin edge connector If you don t want the tx oscillator running all the time there is another mod on the net that ties pin 19 to the circuitry that used to run the PTT antenna relay With the crystal running all the time it is quite easy to hear the repeater without the transmitter being keyed up Keeping it keyed should help stabilize the frequency the initial aging should progress quicker than when only running the oscillator when the TX is keyed 4 The stock transmitter output runs from a right angle RCA jack on the power control board via a jumper to a BNC chassis connector on the top rear of the rack I removed this jumper and added a hooded SO 239 chassis conne
4. ctor with a short pigtail of double shielded coax 6 inches I soldered the pigtail directly to the power control board on the solder side of the original RCA jack and mounted the SO 239 to the upper surface of the rack by enlarging an existing hole This makes changing the power control board a bit of a chore but it eliminates one mechanical RCA connection Exciter Tuneup Step Adjust Meter Test Set Stage and Procedure Plug Selector Revers cn Switch Power Exciter Turn POWER SET control on power 1 Set control board fully counterclockwise Exci FWD The test set should indicate at least 10 2 2 uA 14ua the top of their coil forms away from the circuit board Tune L401 and L402 in that order for maximum meter indication 21uA Go to step 6 of the 3 procedure L401 Exciter FWD Modulator Output Tune L401 for 4 2 minimum meter reading L401 Exciter FWD Modulator Output Tune L402 then 5 L402 3 L401 for peak meter reading L403 Exciter FWD Tripler Output Tune L403 for 3 minimum meter reading 15uA L403 Exciter FWD Tripler Output Tune L404 and then 7 L404 4 L403 for peak meter reading L405 Exciter FWD First Doubler Output Tune L405 for 4 minimum meter reading L405 Exciter FWD PTT must be keyed when making these L406 adjustments Exciter Output Tune L407 L406 L407 and L408 then L405 for L408 peak meter reading 9uA When tuning up an untuned radio you may have to
5. e where the collector of Q10 was 6 Connect a wire from the other normally open contact on the other side of the Line Disable switch to the base of Q 17 7 Drill the front panel and wire a Red LED through a 2 2 k resistor from the collector of Q 18 to ground 8 The station control card pin 16 drives the tx exciter audio through JU1 on the backplane Since our external controller will be responsible for the tx audio cut the trace leading to pin 16 of the station control module edge connector cut on the solder side of the station control module This mod leaves the pin 16 on the backplane available as a convenient place to connect the mic audio cable from the controller Receiver Mods OL EEPS 10778 A tea revr Remove CONN AUDIO SQUELCH BOARD 1 Remove CR 957 on receiver interconnect board the board that lays horizontally between the backplane and receiver board so that receiver will not be muted when transmitter is keyed CR 957 is the diode located between JU958 and JU957 on the right hand side of the interconnect board by the audio squelch board connector use the diode for the exciter mod above 2 Supply the receiver channel element with a ground to enable it at all times For the receiver connect pin 30 of the receiver interconnect board pins J2 bottom row of 30 that come through the backplane to ground Pin 26 Pin 30 is R1 oscillator select Plug the channel element into the F1 position 3 Jumper J2
6. hind the vol squelch panel on the main chassis If you use 3 nuts on each bolt you can adjust the height as required You will need a RCA RCA cable about 10 long to run from the preamp to the receiver casting I salvaged one from a mobile micor unit that had the noise blanker receiver option Power for the preamp is obtained at P954 on the receiver interconnect board The preamp power lead just plugs onto the test post Receiver performance with the preamp is outstanding approx 2 to 25uv for 12db quieting with the squelch threshold being a little over luv Since I did not rack mount the system I changed out the jumper from the RX antenna BNC to the preamp I made a cable with an RCA connector on one end and a SO 239 with hood on the other end with the cable about 8 inches long I then drilled out the unused switch position on the panel below the volume and squelch controls and mounted the SO 239 in the hole This provides front access for the jumper connection to the duplexor anes Jumpers Controller Interface Signal Backplane Location RLC4 DB9 RX J2 14 deemphasized but not Not used Audio 1 squelch gated receiver audio with PL filtering 0 5vp p with 1khz tone 3khz deviation This audio is riding on a 4 5v dc bias RX Pin 21 SCM or raw buffered discriminator Audio 2 J2 15 audio with no PL filtering or de emphasis applied 1 2vp p with lkhz tone 3khz deviation About 0 4v rms noise on no signal 5 COR J2 13 3 6v
7. rough a 22k resistor and the collector lead connects to a jumper to P903 pin 8 This brings a buffered open collector COS out to the backplane 9 Connect a jumper wire from IC 202 pin 6 to the intersection of C 211 and C 213 improves muting performance by using second squelch gate switch 10 Cut IC 202 pin 13 foil trace after trace connects to C235 a 22 uF cap IC 202 pin 13 will only be connected through C235 to ground avoids potential rfi and backplane interactions 11 If you don t want to have to run the Station Control Module in PL Disable mode to listen to Carrier only signals cut the trace leading from IC 202 pin 14 This disables the PL Enable lead on the squelch chip allowing either PL or Carrier signals to be heard on the local speaker regardless of the position of the PL Disable switch on the Station Control Module i 12 Add a 4k7 resistor from J2 10 to ground This gives a load for the PL detect signal I found operation with the RLC was intermittent without the pull down The voltage swing at J2 10 should be 0 3 no PL to 9 0 PL detected with the controller plugged in There is a convenient ground connection down and right of J2 10 Its the heavy trace leaving the J1 power connector 13 Mount the preamp There is a set of holes labeled L1 L2 L3 below the local volume squelch knobs that happen to be in a pretty good pattern for matching the 3 tuning adjustments on the preamp I mounted the preamp on two 10 bolts be
8. squelch open Ov when no signal grounded 7 J2 10 0 3v no PL present 7 with CTCSS PL heard 2 PTT Pin 5 local PTT ground to transmit Station control module Mic TX Pin 16 SCM or 0 5v p p yields about 5khz Audio J5 24 deviation Unresolved issues RX include RX tuneup instructions in PDF include site log document checklist in PDF References This project would not have been possible without the excellent work of Kevin K Custer W3KKC and his repeater builder web site 1 http www repeater builder com rbtip micortxbias html 2 http www repeater builder com rbtip stationcontrol html 3 http www repeater builder com rbtip vhftxtuning html 4 http www gsl net walzyx mods micorbas html 5 http www repeater builder com rbtip stationa amp s html
9. ull then out and file them in the junk box You will not need them when using an external repeater controller TLN4792A 9 6 volt regulator This appears to be an add on option for the unified chassis if it is not being used with base station power supply This board is mounted on the lower rear of the chassis next to the power terminal block and plugs into J1 This is a useful piece if you are running the chassis from a battery powered site with no AC supply As seen in the photo above 12 volts is applied to the 4 conductor terminal strip The heavy red and black wires heading off to the left are a jumper to supply 13volts to the PA stage terminal strip Test Set TLN1857A also marked TLN5900A Exciter Modification SYMMETRICAL CLIPPER AND SPLATTER 9 0 FILTER 1 See reference 1 Remove R401 to increase tx audio input impedance and to remove the dc bias from the mic audio line This is most likely a 560 ohm resistor On the board in my base station this resistor had already been removed OF TLD5321A Exciter with TLN5731APR PL encoder eS FIN 3 Gar 2 There are two options of modification to allow proper keying of the exciter if you are not using the original PL encode deck One is if you never plan on using the Micor PL encoder determine that jumper JU401 JU402 or JU405 some models exists between pins 8 and 10 on the long interconnect pins P902 pins The second method developed is a semiconductor repl
10. une down to the required frequency I had to add a 22pf capacitor across the trimmer inside the element This was enough to give me a little tuning room on the low side about 500hz 12mhz TFD6111APR exciter filter bandpass of 124 161mhz 3db Note a TFD6112APR 145 182 3db may be used or re tuned for the ham band if you cannot locate a lower split unit TRN6971A PA assembly 110watt pa with 70w intermittent heat sink this PA assembly has a heat sink marked TLD2152B and the actual PA board marked TLD5942A There are 4 transistors in a row on the final amp marked M1134 TLD8620a power control board TFD6101A output filter brick A TFD6102A 192mhz low pass filter will also work Receiver components modules preamp TLD8422B 150 8 174mhz this is a high band preamp but seems to tune down fine into the upper 2 meter band Use a TLD8421B 132 150 8mhz if you can find one K1005A channel element with xtal for R147 88mhz xtal gt 17 7311 1mhz 9 11 7mhz 147 88 TLD8272B receiver board 142 150Mhz split TRN6006A station audio squelch board TRN6002A pl decode board with TLN8381A 100hz reed TLN5648A receiver interconnect board Control Modules Only the Station Control Module is used in the card rack It should be plugged into the second edge connector from the right hand side of the card cage You may find other cards in your card cage such as timeout timer line driver squelch gate and various tone modules Just p
11. use a digital meter from pin 5 lower right of the exciter test socket to ground because until all 4 coils are peaked the test set will show very low 5 readings Exciter FWD Pre Alignment If the exciter is completely untuned and shows no r Coils meter 3 readings set cores of all tuning coils to the top of their coil forms away from the circuit board and proceed with step 5 If the exciter shows meter 3 readings set cores of all tuning coils except L401 and L402 to 3 Exciter Tuneup L407 PA REV J Exciter Output Move the metering L408 plug to the PA Tune L408 and L407 10 1 for peak meter reading 11uA As a final check for tuning I measured the output of the bandpass filter into a 50 ohm load and obtained 500mw spec is 400mw required to drive PA stage Station Control Module Mods y j erise Q10 removed pink wire from Line di es l new wire to Q17 base s LN B Station Control See reference 2 for a more detailed description 1 Completely remove Q 10 and Q 15 from the board This disables the ability for an outside source from inhibiting the PTT 2 Clean out the hole that the collector of Q 10 was in 3 The common center pin of both sides of the Line Disable switch should go to ground from the factory 4 Unsolder the pink wire that is connected to the top side of the switches normally open contact from the circuit board 5 Solder the removed end of the pink wire in the opened hol
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