Micor transmitter for repeater service
Contents
1. 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 measurement using the dom term 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 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 key2. are the TLPs Non parenthesis figures are absolute actual operating levels and as mentioned before may be at different levels from the TTLs 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 This 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
3. 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 Dypasses whatever squelch setting using only tone to keep it active More is discussed later in this document SRG means Spokane Repeater Group a non 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 is later referred to as Mouser FM Frequency modulation is the common way to send intelligence in the LMR analog world There are two ways to frequency modulate a transmitter PM and FM Phase modulation is the easiest design with good frequency stability however lacks audio response However PM has natural pre emphasis which works well for LMR standard On the other hand FM has much better response flat audio at the cost of more complex engineering to keep stability With synthesized PLL transmitters this
4. cable speaker control head and microphone The basic ordering option was 1 2 3 or 4 frequency channels controlled with the head 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 references Some call these benchmarks or baselines While old methods used linear micro
5. ones Without any of the front panel being built this may be a good time to run the transmitter though its paces to look for any problems overlooked In an extreme bad case you could stop here and start building a new one Just clip the needed wires for power control and put a load on the RF port etc Mechanical The mechanical part of the project is working with the panel drilling mounting the standoffs and fastening with screws and bolts Most of the bolts are 8 32 with phillips head Phillips head and pan head make it much easier to work with especially in an angle such as securing inside a cabinet Even the terminal blocks TB 1 and TB 2 have these types of screws to hold the wires and lugs TB 1 is Cinch Jones 140 series size 375 in holes using a 6 32 machine screw Molex brand has the equivalent in the phillips screws Mouser part 538 38770 0110 for the 10 terminal For the wires crimp them with 6 spade lug for 22 18 gauge wire part 517 2232 For the PA power TB 2 is also available from the same vender 142 series size 563 holes using 8 32 machine screws Part 538 3821 1 0102 for the 2 terminal rated at 30 amps For the wires you can crimp them with 8 spade lug for 12 10 gauge wire part BS 33 8 For best high current contact area use full rings instead for 12 10 gauge wire part 517 1217 In any case the Author prefers to crimp then solder all lugs 12 PA heat For high duty cycle the PA g
6. Motorola Micor transmitter for repeater 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 Motorola made a Micor series of radios both base station and mobile This discussion is mainly on the mobile which was manufactured in the 1970 s Its a very rugged heavy mobile radio unit drawer unit if you will that works with an accessory group consisting of a power
7. ally for the mobile type of transmitter more on this later Running the fan 24 7 wears it out A better choice is have it come on only when needed This is done with a thermo switch normally open then closes at 100 F For redundancy two of these switches are mounted in parallel Use a good layer of heat sink compound under each switch As shown in the left image you can optionally countersink the screw head into the radio s heat sink This is also handy if the screws you have on hand are a little too short Also you ll need to make two notches for the PA shield to clear the screw heads The last area of discussion is the RF output section An interface plate had to be built to mount the connector and give more shielding on that end of the chassis Steel plates were chosen and several being built as shown here for the connector The 8 holes will be 7 64 and the one center 5 8 In the event the holes don t line up perfectly you can enlarge the small ones with a 1 8 bit The old OEM coax with a RCA connector at one end was used to plug into the power control board The other end was cut off and prepped for soldering directly onto the new N connector Shown here is the completed subassembly back and front ready for the radio 1 Now mount the subassembly to the radio s chassis There are four 4 40 type holes already there for this The 1 2 screws are too long so either cut them use washers or find 3 8
8. ble wires run out to TB1 for external control In the picture above notice the enable lug jumper on TB 1 terminals 7 and 8 for normal F1 operation Terminal 10 is the fan control discussed later Shown on the left are the two audio coupling capacitors that now use the old F4 line as the input flat audio TLP is about 3 dom To start remove C457 and replace that spot with a wire jumper now called JU457 Also jumper this point to the eyelet feeding P902 pin 5 This now functions as a ground run Remove C410 and replace with a 4 7uf 25 v electrolytic capacitor with positive lead going to P902 pin 7 This is a general filter for the regulator Optionally for general cleanup you can remove JU401 JU402 JU403 JU404 C465 and C466 Remove C405 then remove C463 and install a new tantalum with the leads reversed the positive lead going to CE1 pin 4 and the negative lead going to the F4 select line where part of C405 was For the second frequency option install the same value to with its positive lead going the CE2 pin 4 The other lead can be shared with the F1 cap s negative lead going to the F4 select line This is now the Tx AF input P902 pin 18 The board will need 12v A and regulated 9 6 to operate For OEM mobile the latter gets it from a regulator on the middle board which is not used for this project For this project the LM 7810 3 pin regulator is used The output goes through a simple rectifier diod
9. ch the filter it plugs into so cutting it is not an option If this is the case with your board remove the broken parts of the coax and board s eyelets With a new piece of shield from a spare piece of coax and solder wrap around the damaged shield to extend it to a point it can be soldered back to the board as shown here a repaired shield on the coax output Also the shorty RCA plug s ground fingers get loose over time It s a good idea to press all four in slightly for a tight fit on the filter module Be careful not to slip and bend them in too far when doing this i a a o LAAAAALALILLAAAA PRR 5a 1p OOP Wy a pho i Now you can install the exciter board in the chassis as show here Then do the wiring for the power control board 3 wires ground A and control voltage The latter connects to the PA control transistor In this view a feed though cap was used however OEM just has the wire go through a hole in the chassis Above view is the top of the chassis The picture above is before the exciter is installed Did you notice the two silver boxes They are filters for the transmitter The one on the left is a band pass filter Z501 for the exciter board s output The one on the right is a harmonic filter Z502 on the output of the PA section Z502 is not tunable but should be broad enough to make it to the top end of the amateur 2 meter band Z501 is narrower in range and
10. e 6 tenths voltage drop causing the output of 9 4v which is close enough to the stock 9 6 voltage Control To control the keyed circuits a TIP42 transistor is used with its associated parts The physical location has been under research for several years The left image is the older obsolete mounting location for the 9 6 regulator the PTT switch was located elsewhere More recent versions 2009 and later have the parts mounted on P401 which was the PL pins that are not being used First to make is the regulator with a very small footprint Then install a 22 uf cap on its output which is required to filter noise at this point Then add the dropping diode to get the 9 4v output This sub assay can be later mounted on the P401 pins Below shows several being made as a production line to produce several transmitters with their regulators Next remove P401 pin 1 and cut the rest of the pins down in length so the top of the installed parts will clear the chassis and tin them Install the 10v regulator and PTT switch on the pins per the diagram for the interconnect and these pictures Install a diode cathode on pin 1 with a 1K resistor in series with its lead to the switch s base The diode isolates the 9 6v to outside 12v equipments PTT and other LED circuits on the front panel Remove JU405 and install a 2 2K resistor in its place 2 7K is okay for a substitute In the eve
11. ets very hot The OEM 15v supply contributes to the problem A solution is running the PA at a lower voltage with the KPS 20 supply Setting the power out to 48 dbm will draw 16 about amps from this supply This and installing a fan control unit FCU keeps the heat problem under control Documentation on both these items can be found on SRG s web site With this arraignment typical time for heat up to signal the fan is 6 minutes while cool down to turn the fan off is 14 minutes with the 100 F switches Shown here is the completed project with labeling on the front panel serial number 4 ready for service DC Power PTT O r gt v 4 2 2 5 Normal Tesi bia Disable Normal VHF Transmitter Tuning and checkout Install the appropriate channel element for your frequency The formula is carrier frequency divided by 12 for the crystal frequency inside the channel element You might consider sending the entire channel element for crystallization so it can be compensated as well Doing this also has the advantage of the crystal company being responsible for the proper formula all you need to supply is the carrier frequency for the model of this radio Next tune the exciter board as usual per the service manual In the event its not available you can use the following procedure running the PA voltage at 10 The meter socket pins 1 7 are functional either with a stock test set or a simple
12. frequency while most FM transmitters has the diode in parallel to the crystal For FM transmitters most have the anode to common ground and usually across the crystal 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 final operating frequency For example a typical LMR VHF transmitter would be 12 times or a tripler driving 3 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 project Repeater usage For repeater use will require a custom build chassis You are required to Know the micor inside and out This is especially true if you are converting a high range 150 8 174 MHz transmitter to a low range for the amateur band Repeater building experience is needed as well One little component mistake can cause hours of frustration If this is your f
13. hannel elements and PTT switch Then jumper P902 pin 9 to pin 13 This feeds the keyed 9 6v to the audio circuits IC Q401 and the multiplier stages Shown here is the exciter board with the completed version C modifications This is SRG s new standard as of 2014 If you are using the exciter TLD513x observe note 409 on the schematic of manual 68P81008E40 L It says to bypass R431 33 ohm for 1 4 frequency operation It s located on the input of 1C401 pin 14 Other radio versions don t have this And some compa types don t use the 10401 either Sometimes there s a slight heat issue problem with some boards The second to the last RF stage Q405 may run a little too hot SA a during long transmissions In this case you will SSS 2 Te at a Ee P VE 8 need to reduce the heat but still provide ah l enough RF drive to the PA The RF stage of Q405 s collector voltage is lowered a little by adding a 27 ohm 1watt resistor in series with L413 circled in the left image First check to see if the transistor gets hot before you do this modification because you will loose about 14 db output on some boards which could be a consideration This equipment is old and subject to wear The floppy RF output coax is no exception During normal mobile use plus modification handling can cause most or the entire wire shield to break off which would cause level and interference problems The coax Is just long enough to rea
14. ion FM is also referred to deviation of the carrier at an audio rate For amateur radio 100 system modulation is normally 5 KHz Other areas States and or commercial 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 normally on equipment in reference to TTL TLP provides easy reference to any parts of the system for measurement and alignment 0 dom is referenced to 1 milliwatt at 600 ohms Therefore a transmitter AF input with a TLP of 0 dbm with a TTL of 0 dom tone input would fully modulate the system If the far end receiver was set up the same its output a 0 dbm tone as well A 6 dB drop in voltage level would reduce the modulation in half and so on In general 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 Absolute levels are specific measured operating levels not to be confused with TTLs 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 sometime used in diagrams and on the physical equipment s ports or I O connections Figures in parenthesis
15. irst time seek help from a local repeater owner to avoid problems and equipment damage For repeater use will be a single frequency operation The OEM mobile radio has several sections inside Two of them are discussed here the separate transmitter and receiver sections each of can be easily removed and mounted on a 2RU 19 rack panel The appropriate controls then can be installed on this panel eliminating the need for separate cables and controls both of which take up space and clutter in a repeater cabinet or rack The rest of the mobile unit is discarded or otherwise used only for misc parts This unit is set up for negative ground This arrangement is similar to the compa station unified or non unified chassis without the control circuitry However one large advantage to using a mobile is each part can be installed at separate sites with minimal space Therefore each of the transmitter and receiver will be a covered on separate documents found on SRG s web site For this document only the transmitter is covered The first custom built transmitter pre 1990 started the compact package Shown here is serial 1 Serial 2 changed to the white panel standard Shown here is the front of a finished transmitter Notice there s a switch function to lock on the PTT line for transmitter testing under load It was decided a ON Center OFF ON switch is sometimes awkward to use disable being in the center position one may run the switch
16. 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 all 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 diodes have P N a 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 intelligence in the form of audio acv voice will cause the RF circuit to change in frequency at the same rate thus creating direct FM Special diodes are made for this purpose called a varactor diode veri 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 modulation 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
17. iter board There are several versions A from the 1990 s and recently September 2009 version B was developed however not proven in service Version C appears to be the best method and is the version to be used for all SRG transmitters All versions are reviewed here Version A Only the channel element is running full time This version keeps the crystal and channel element running full time via the continuous 9 6v line This improves stability The other circuits after the CE are off during standby condition that would include pulse amplified C401 mic audio IC402 CE buffer Q401 pulse amplifier Q402 and the multiplier stages of Q403 Q404 and Q405 via the keyed 9 6v line For this version cut the PCB run between IC401 pin 9 and CE4 pin 2 and C406 area There s a straight run at 1C401 right near it s pin 16 is a good place to make the cut This isolates the continuous and keyed 9 6v lines Jumper P902 pin 4 to pin 8 This feeds the voltage input of the PTT switch and other continuous 9 6v circuits Jumper P902 pin 9 to pin 13 This feeds the keyed 9 6v circuits and components such as the IC and multiplier stages Jumper the eyelet near P401 pin 7 to the area of the cut just before C406 There are two eyelets that work great for this one next to the pin 7 and the other above C406 This completes continuous 9 6v to feed only the channel element continuously during standby state Version B The channel element some transist
18. may need tuning The image shows a L written on them indicating they both are the low range thus don t need anything done for operating in the entire 2 meter amateur band of 144 148 MHz Z501 comes in two band ranges Model TFD6111 is the L 182 150 8Mhz range and the TFD6112 is the M H 150 8 174 range If you have the M range it will need tuning which can be done only while the cover is in place However you can modify the cover by drilling 5 holes Keep them small to not affect the properties but enough to get a slim tuning tool inside 3 32 is suggested Take care to line up the holes right over the coil forms Then re assemble and install the filter for tuning Be aware that some filters were built in the factory with excessive sealer and may have to be discarded for another one The completed filter should look like the image on the left The filter output appears not to be 50 ohms It s best to tune the filter with a spectrum analyzer however peaking it with a power meter works in most cases For final tuning this filter needs to be in the OEM circuit arraignment driving the PA and observing the RF level at transmitter output port 10 The next area of discussion is the PA high power section OEM specification for intermittent duty is 50dbm however for repeater use this should be lowered by 2 db at least For repeater use besides dropping the rated power a few db fan cooling is also necessary especi
19. meter If using the latter typical voltages are as follows when properly tuned a RS22 204C meter was used for tuning Pin 1 is IDC audio level no tuning here Pin 2 is channel element output typical 865v no tuning here Pin 3 is the pulse amplifier output of Q402 peak L401 and L402 Typical voltage is 1 877v Pin 4 is Q403 output or Q404 input peak L403 L404 Typical voltage is 1 174 Pin 5 is Q404 output or Q405 input peak L405 L406 Typical voltage is 529v Pin 6 amp 7 is ground Peak L407 L408 for power out using a power meter or spec analyzer Minimum level is a 26 dbm to properly drive the P A section Typical level is 28 451 dom 700 mW for math challenged folks On the power control board turn R611 fully CCW min resistance R610 will be your power control setting For transmitter output levels intermittent duty rating is 50dbm 100w 49 5 is 89 13w 49 is 79 43w 48 5 is 70 8w and 48 is 63 1w As you can see watts change is overrated when rating it with log Parts Listing For front panel amp chassis 1 Panel 19 rack type Bud radio PA 1102 WH 16 Screws 8 32 x 1 2 for mounting the panel to the chassis 8 standoffs 1 8 32 thread female female All Elect SP 284 35 each for the panel mount 1 terminal block 140 size 10 position Mouser Elect 538 38770 0110 TB1 4 Screws 6 32 x 1 2 for TB1 4 Nuts 6 32 for above 1 terminal block 142 size 2 positio
20. n Mouser Elect 538 38211 0102 TB2 4 Screws 10 32 x for TB2 4 Nuts 10 32 for TB2 13 2 Switchs SPDT miniature Mouser 10TC320 DPDT okay 1 Switch DPDT miniature Mouser 108 0010 EVX or use this number for all three switches 1 Jack 4 pin Hosfelt Elect 4PMCS for panel mic jack or MCM electronics 27 7977 1 Fuse holder 3AG All Elect FHPM 31 or Mouser 576 03420004H 3 LED green defused T134 for power indicators 2 LED red defused T1 3 4 for PTT keyed v indication 1 LED red defused blinking T1 3 4 for PTT lock on indication 1 LED yellow defused T1 3 4 for fuse indication 7 Resistors 1K for the LEDs one is mounted in the PA section 1 Pin jack black For the 9 6v regulator 1 IC regulator LM7810 220 case 1 Capacitor tantalum 22uf 25v mylar substitute is ok 1 Capacitor electrolytic 4 7uf 25v 1 Diode common rectifier type 1 amp 100 piv for the 6 10 voltage drop from the regulator For the 9 6v switch keyed 9 6v 1 Transistor TIP 42 220 case 1 Resistor 2 2K 1 4 watt 10 2 7K okay 1 Resistor 1 K watt 10 1 Diode 1N4148 914 type to isolate the internal 9 6v reference to the outside 12v PTT equipment For the PA section 2 Switchs thermo type normally open closes at 100 F Mouser 802 STC 100 4 Screws 4 40 x 1 2 for thermo switch 4 Nuts 4 40 for thermo switch some heat sink compound for the switches For the ground bus
21. nt the components needed replacement is an easy task working with the pins as solder mounts In the right picture notice the blue capacitor next to Q406 If its larger in size move it slightly inward angled leads so it clears the chassis rail when installed Here s the modified exciter board to the extent wires are soldered to the P904 I O pins with heat shrink to increase reliability Some of the unused pins are removed to assist the ferrite bead clearance some others are left The beads can reduce RFI on the lines if the site is RF hostile A drop of glue will keep them in place The unused pins that were removed are 2 3 5 6 10 and 14 Control versions To control the transmitter some 9 6v stages are hot during standby while latter 9 6v stages are cold mainly the multiplier stages When keyed they become hot causing the transmitter to output RF Also the OEM arraignment has Q406 the last output stage Q408 in the compa style live all the time from the 12v A source Being a class C device it only has output when the earlier stages are hot For this project this section is kept as OEM There were several different SRG versions of exciter boards developed This involves the control method such as what circuits are hot during standby and which ones are switched to key the transmitter These versions were developed in September 2009 based on research from 2000 using the TLD5132A exc
22. ors and IC are running full time This version keeps the crystal and channel element running full time via the continuous 9 6v line This improves stability Some of the other circuits after the CE are also running during standby condition via the continuous 9 6v line that would include pulse amplifier IC401 mic audio IC402 CE buffer Q401 and pulse amplifier Q402 The multiplier stages of Q403 Q404 and Q405 are off during standby state via the 9 6v keyed line For this version cut the PCB run between P401 pin 9 and Q402 emitter There s a straight run closer to the former to make the cut This isolates the continuous and keyed 9 6v lines Jumper P902 pin 13 to P902 pin 8 and pin 4 This completes the continuous 9 6v line Jumper P401 pin 3 to pin 9 This completes the keyed 9 6v line This version has not been tested proven in actual service Version C Only the channel element is running full time This version is the same as version A except two shorter jumpers take the place of that one long one running over to the C406 area for the continuous 9 6v it looks cleaner To recap the procedure for version C Cut the PCB run between IC401 pin 9 and CE4 pin 2 and C406 area There s a straight run at IC401 right near it s pin 16 is a good place to make the cut This isolates the continuous and keyed 9 6v lines Next jumper P902 pin 4 to pin 8 and pin 17 Then jumper CE3 pin 1 old F3 line to pin 2 This feeds the continuous 9 6v to the c
23. s 1 6 32 x 3 8 screw longer ok if you use many lugs 2 lugs 6 ring for AWG 14 16 more lugs if you wish more ground wires For the antenna port 1 RF connector N type female chassis 4 hole flange Ampenol RFX 1 Coax jumper teflon type 50 ohms from OEM power control board 1 steel plate gu 16 18 2 x 2 8 7 64 and one 5 8 holes to be drilled 4 4 40 x 1 4 screws to mount the connector to the plate 4 4 40 nuts for above 4 4 40 x 3 8 to mount the plate to the chassis For the modulation section channel element pin 4 2 Capacitors tantalum 4 7uf 25v 2 freq operation Mouser Elec part 80 1T354C475K025AT Other needs Shop with tools and test equipment well lighted 40 hours typical time for this project Glue hot and epoxy for holding LEDs wires etc in place on chassis amp panel Labeling tape or Marker for labeling the front panel Misc wire AWG 20 22 or 24 black brown red orange yellow green violet and other colors as needed and a few lugs Some solid for board jumpers CAT 5 orange wire is good This 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 2006 updated 8 29 13 2 23 14 4 19 14 4 20 14 4 21 14 4 23 14 6 4 14 6 5 14 6 11 14 6 12 14 6 15 14 6 16 14 6 17 14 14
24. 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 Coded squelch System 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 and a HUB for mobiles and base station control AND squelch means it takes
25. to the down position and keep the PTT on so this was changed to a ON ON switch as shown here NHE Tranier 1 ou ema PM BIT Teer MIC EW LOCE DH 2014 redesign updates Serial 4 and later A logical and standard layout needed to be realized This includes additional indicators such as 12v 9 6v keyed 9 6 PA power and PTT activity in the appropriate colors The correct terminal block placements were done for consideration of the exciter s I O runs etc and short PA wires Behind the panel the chassis position was moved to the left for improved fuse and RF port clearance on the right side The three switches on the panel are arraigned properly The left is the main power middle PTT control and right PTT lock on test position Both PTT switches have to be up for this test function to work A red flashing light reminds you it s in this mode for testing The picture was taken during a load test and is the final layout Exciter The exciter board is the heart of the transmitter It has the frequency determining element channel element with the crystal the modulation section and all the multiplier and amplifier stages to a usable level of 26dbm to drive the PA The type of modulator is very important for a flat system therefore only the 4 pin exciter board is used for this project older versions with the 3 pin phase modular where modified for direct FM As of 2014 it s capable of 2 frequency operation The F1 and F2 ena
26. volts 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 specifications call for a better way as you will see in this documentation References can be expressed in a few acronyms Normally a tone of 1 KHz sometimes 1004 Hz is used for a testing a 2 way VHF UHF transmitter or receiver TTL Test Tone Level is referenced to 100 system modulation in this case F M Frequency Modulat
Download Pdf Manuals
Related Search