Batboard

Hello, I am having problems with a GM300 model M44GMC20D3__. This radio has no way to configure the accessory connector in the RSS. Plus the radio does not rx. When hooking the controller to it for the rx it does not work with or without. If you place the TX plug to it it hums real bad when you transmit, but does not hum when you tx via the mic. The repeater came with 2 GM300's, controller, cans, and PS. It was working about 2 years ago then sat on a shelf.

I have another GM300 model M04GMC29C3__ that I intended to use as a rx radio only due to the 10watts. The current TX radio wis working fine. The problem with that is when I configure the CSQ on pin8, the car light stays lit on the controller until there is a received signal then goes out. I have tried for hours to configure it to work until we can get a Maxtrac for the rx radio.

Please let me know if I can re-flash the GMC20D3 to a GMC29C3 to get the rx working again and get to the accessory connector screen again,

Any input would be appreciated.


Mike

Mike,

The output for the RUS, which includes the PL decode AND the carrier squelch, is configured for Zero true and you need a pull-up resistor to 5 volts. A 4.7 Kohm is what most use.

No way to do any flashing on GM 300 radios.

The hum on transmit is due to incorrect interfacing.

That model number should be an 8 channel GM300.
You can't "program" the accessory connector as you could on an 16 channel ( or more ).
Pin 8 is RUS going LOW only. Can't be changed.
With a mic dummy plug ( or a mic "on hook") the RUS is for both PL valid and carrier.
The other accessory pins should be:
2 Mic audio
3 PTT
5 Flat TX audio ( instead of Mic )
7 GND
11 Discriminator audio

Wow, Thank you so much for all the input. We got it working.

Thanks for all the help.

Mike