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Hi all, I'm currently working on a pair of Motorola GM900 to replace the TX/RX in one of our UHF repeaters. I could program them with a RIB on the right frequency and they both work, the repeater is working OK. Now I want to align them as precisely as possible with the "tuning procedure" as found in the service manual. Unfortunately, this procedure needs a GTF180 test box which I don't have. Nowhere is the GTF180 described and where the different signals have to be fed into the radio. The transmit deviation balance says a 80 Hz and a 1000Hz is to be injected into the test box. Does someone know WHERE these signals are to be fed or has a GTF180 diagram and manual ? Thanks for any help, 73 Patrick

A fellow ham brought over a TK690H that was converted to 6M from the RB article. It worked OK on 6M, except that the VCO voltage was fixed and did not change with the frequency change. Normal range is greater than 1.5 V at the highest frequency to less than 8.0V at the lowest frequency. Also the varactor front end tuning did not change with frequency, so there must be a connection between the two. I think the VCO voltage was fixed to around 5.0 V. The brass rods were protruding about 3 mm above the coil forms. I just did a couple more TK690H conversions on the older but better radios with all number serials starting below the number 3..........I say better because of narrower receiver modulation bandwidth of around +-7 KHz vs +- 8.5 KHz on the newer radios with "E" bandwidth ceramic filters instead of "F" bandwidth ceramic filters, for a better signal to noise ratio. Also the older transmitters with the bipolar PA transistors are more efficient on 6M than the mewer radios with MOSFET PA transistors. The older radios should do 105W with 15A draw all across 6M. Another ham from the west coast (sorry don't remember the call) on this group site suggested that he just removed the 2 chip caps in parallel with TC301 and TC302, rather than inserting brass rods into the coils. I tried that first, but that was insufficient on receive above 53.5 MHz, so I suggest doing both, but with a shorter (3mm) length of the 1/8" brass rod. This way both the capacitance and inductance are lowered possibly about the same amount, and the brass rod is confined completely to inside the coil form and it is also completely sealed to moisture. I used Permaseal Ultra Blue RTV first placed inside the coil from and then the 1/8" rod inserted centered inside and then covered over with the Permaseal. See pictures. The first shows the tube of Permaseal and the 2 chip caps still in place, and the second with them removed on another radio. John W1GPO

I thought I'd share my recent ammo can repeater build. The goals were: As small as possible Portable AC and battery power DMR and FM Good performance Parts list: 2 Motorola CDM1250 radios with control heads removed. Repeater Builder STM32 MMDVM paired with a Raspberry Pi 4. 100W Mean-Well switching power supply. Mobile duplexer 3D printed assembly that holds all of the parts together Fat 50 PA-108 Ammo Can 80mm Noctua fan Build notes: In order to fit size constraints all wiring and cables are purpose-built. I couldn't even use the standard SAE power connectors for the radios. I used tefzel mil-spec wire for all wiring. To optimize cooling for the TX radio there are 3 front exhaust holes for that radio compared to one exhaust hole for the RX radio and duplexer sections. There is a foam sheet top and bottom of the assembly between the assembly and the can to hold it all together tightly and provide some shock protection. The TX radio is set to 20W. At 20W the radio only draws around 5A, so the small power supply is more than sufficient. The cooling fan is quiet and runs continuously. Temperature rise is minimal even with a long stretch of continuous use. The whole thing uses about 800ma at 12V at idle. I started with pi-star on the raspberry pi but could not get it to work without an internet connection. Since I wanted to use this in the field with no internet, that was a deal breaker. Fortunately WPSD will boot up find and work without internet. So I'm using WPSD. I'm thinking I can build a custom Lithium battery pack with 21700 cells that will fit in the space on top to allow for 100% self contained field use. That will be next. Performance has been very good, better than expected in fact. Larry, N6TXX

Curious if anyone else has one of these & what they think of them. Measall KC901J is the particular model I'm looking at. A while ago I picked up a LibreVNA to help tune duplexers. Its pretty nice, but it uses a PC for the screen & software. Thats a minior drawback in some ways. So I thought I'd look around at some other equipment that's more portable & stand alone. Then seen these KC901 models from Measall.

Hey Guys: I have an MTR2000, which has worked flawlessly since I got it in the summer of 2020; a real workhorse! Lately, I have found the station non-responsive and upon inspection, I find the first LED (the left most LED) red. I have to power cycle the station to get it to come back to life (it's an AC powered station, btw). Today, I spun up my old XP box and used the RSS s/w to run a diagnostic check... everything seems to be OK (although I am not sure why the SCM RAM and ROM were not tested): I also looked at the Error Log: Interesting... only 3 lines? I left the PC connected and RSS running for an hour, when I returned, there are a couple of new entries: The lockups / station freezing are happening about once a day, sometimes once every 2 days. Any ideas? Thanks! Ramesh, VA3UV, WA3UV