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what is the easiest and most cost efficent way to link a cdm750's recieve audio into a gr1225's transmit?

Hi John,

I read your PM at home the other night & had intentions of contacting you once I was back using my work computer, then promptly forgot.

Wiring the CDM link radio into a GR1225 is relatively simple. Everything is done through the accessory connectors.

In the GR1225:

1) In the radio wide screen, set the "operation mode" as "linked repeater".
2) In the external accessories screen, set the "ACC External" as "General I/O".
3) Set Pin 8 as "CSQ detect" or "PL/DPL & CSQ detect" if you're using a PL/DPL. Set it as an "output", active "LOW".
4) Set the "RX Audio Output" as "Flat", and the "RX Audio Muting" as "Muted".
5) Set the "External Mic" as "External Mic Audio".

In the CDM, the programming is similar:

1) In the "Radio Configuration"-->"Accessory Pins" screen, set Pin 8 as "CSQ detect" or "PL/DPL & CSQ Detect", output active low.
2) Pin 3 should be defaulted to "External MIC PTT", if not, change it.
3) In the "Accessory Configuration" screen , set "External PTT Audio Source" to "Ext Mic Audio".
4) Set "RX Audio Type" to "Filtered Audio".

For the wiring, it should be as follows:
I don't recall off-hand, but I believe there are some audio adjustments in the 1225 alignment screens you can play with if the sound isn't quite to your liking. When I was done, I couldn't tell the difference between local repeated audio and linked audio. Good luck,

Todd

Thanks for the info, I thought it could be done this way, I remember reading somewhere about it, but could not find it in a search on here .

I know this is an old post but since it is related to what I am doing right now.... I'm not using a CDM 750 but I have seen this listed elsewhere. In the Maxtrac I'm not seeing an option to change pin 3 so can only hope it is PTT. In the programming of the accessory connector it begins with pin 4. I am trying to get a 6 meter Maxtrac and a UHF Maxtrac to crossband both ways but right now can only get them to go one way. I have ordered another cable just in case the bidirectional one I have now is not right. Eventually I plan to hook the 6 meter maxtrac to a UHF GR-1225 so it will bring some activity to 6 meters.

kb3awq wrote:I know this is an old post but since it is related to what I am doing right now.... I'm not using a CDM 750 but I have seen this listed elsewhere. In the Maxtrac I'm not seeing an option to change pin 3 so can only hope it is PTT. In the programming of the accessory connector it begins with pin 4. I am trying to get a 6 meter Maxtrac and a UHF Maxtrac to crossband both ways but right now can only get them to go one way. I have ordered another cable just in case the bidirectional one I have now is not right. Eventually I plan to hook the 6 meter maxtrac to a UHF GR-1225 so it will bring some activity to 6 meters.

So...what exactly is your question? You are correct, pin 3 is hard coded as PTT (active low) in the Maxtrac. Beyond that, not sure what you're asking.

Just that I had seen it posted online somewhere about changing pin 3 but thats not possible in the programming. I have decided to use different equipment which is probably a better idea anyway due to the age of the Maxtracs and if my computer were to go I wouldnt be able to change things anyway.

Ok. Well, in terms of making a proper bi-directional cable, the PIN numbers I give also apply to the Maxtracs, if you decide to try it out.

With Maxtrac/Radius radios you should add a 2,2 K resistor and a 2uF capacitor in the RX audio line from each radio. This gives the correct level and isolates the op amp in the radio.

+ side of the cap towards pin 11.

Ok, trying to get this set up today. I made the cable, but have a question:

The setup I have is a UHF repeater with PL (186.2), and a Low band CDM which is CSQ.
Pin 8 settings: On the repeater side, PL & CSQ detect, while on the CDM set to CSQ detect>

Does this sound right???

thanks!!

Yes that would be correct.

Thank you!!! Will let you all know how it turns out!