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Repeater setup question



Okay, I have my 2 Motorola CDM750’s cable to my Duplexer. My question concerns the ID-O-Magic controller connected to both CDM750 via their 16 pin interfaces and the raspberry pi running the MyGMRS software.

Do I connect my pi running the software using the Pi USB port and the ID-O-Matic mini USB? I’m confused passing data between these two devices.

if I can’t use the ID-O-Matic, then must I have a duplex cable built to handle this?


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Rich is gonna need to comment on the configuration of the MyGMRS software.  I don't believe that is a repeater controller though, only an interface to the network.

That being said, you need somesort of connection between the two radios so that the RX from one will Key the others transmitter and pass the audio from one to the other for it to act as a repeater.  This can be done via a repeater controller or a simple back to back cable that crosses the RX audio and COR from teh receiver to the TX audio input and PTT of the transmitter.  It's fairly straight forward.

Once that has been established the ID-o-Matic will need it's audio output connected to the TX audio input of the transmitter radio and the PTT of that radio.

The Pi running the system interface software will need to be connected to the TX and RX audio and the PTT as well. 

You will want to pull the RX audio out of the receive radio via the flat / filtered RX audio pin and NOT the speaker output pin.  This will give you a good level of signal to inject into the transmit radio that will not overdrive the transmitter.  You will also want to set the receive radios programming to filtered audio out on that pin.

Turn off all the compression and companding on BOTH radios.  It makes the audio cleaner.

The TX radio will need the input level set to 200mV.  the choices are 80 and 200.  The output of teh RX radio is always gonna be 200 at 80% deviation for whatever bandwidth you have the receiver set to.  In the case for GMRS it needs to be narrow / 12.5Khz. The transmitter will also need to be set to narrow band.  This is configured in the channel programming part of the codeplug.  Set the RX radio for RX only on the channel and set all the tones to off.  No need to trasnmit the powerup tone and the like over the air.

When you were talking about the USB interfaces, I assume you were meaning the USB sound cards.  You will need two,  one for each Pi as they are doing different things on different Pi's.  If there is a way to share them I don't know it and I wouldn't want to screw with attempting to do that level of configuration on the Pi's anyway just starting out with them.


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