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Repeater will not tx or rx in a standalone state



I’ve posted a couple or three questions here about about my repeater. Members have help me along with my collection of equipment. Thanks everyone for that help.

Now, I have constructed a repeater using the 2 - CDM750’s. One for Rx only at 467.xxx and one for tx only at 462.xxx. These radios are cabled to a Motorola Celwave duplexer using low-low 142 cabling. I am using a RIM-Maxtrac RM cabled to a Pi running the GMRS software. With all of that being said, it will not pass the first bit of data, voice, or even be heard from the antenna side. I see the TX light on the TX radio and the RX light on the RX radio as I key my HT, but NO voice. 
Here’s the part I do not understand. I CAN hear any call from my antenna on my RX CDM750 as clear as a bell if a have the volume off of zero and I can TX to a friend a mile or so away by using the mic plugged into the TX CDM750 and hear myself on the RX radio!

What am I doing wrong? I’m just before calling it quits and throwing in the towel.

Any ideas??


Ron, WRPJ594 

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You can order a back to back repeater cable for under $20. Throw all that other stuff out and just use a back to back to verify you have stuff programmed correctly. 

As said in previous posts one pin on the RX radio must be set for COR. Normally pin 8 or 14. RX audio would leave the radio on pin 11 (Discriminator). TX radio PTT is Pin 3 and TX Audio is Pin 2 on the CDM. You need to program the CDM to use Flat TX audio and not Mic audio. 


Litterly 3 wires can be used to make a repeater with no functions. 


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Sort of a blind guess, since I don't have any experience with the CDMs or the rim-maxtrac/RPI setup. With what works and what doesn't , it sounds like the issue is in the audio path from your rx radio. It's clearly hearing and keying up the tx, and that you can hear on the Rx radio itself says tones probably aren't the issue. 

Is it feasible to shuffle the radios, use the tx radio as the rx, to rule out an issue with the Rx radio? I'm think if there still no audio, the issue is between the radios, cable or a setting in the rpi.

One other thought is if there's something in the programming that needs to be done to enable audio out on the CDMs.

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Problem resolved. Configuration changes in both RX and TX CDM750 per comments here and another site and a tweak in SimpleUSB.Conf. Fortunately, I just procured a copy of The CPS software.

After a reboot and and run of repeaterfinder.sh, I’m now listed as repeater 22802.

Now, I just need to figure how to manage my node!

Thanks everyone. 


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