Arduino Repeater Controller: Part 1

I’ve decided that I want to build a repeater controller using an Arduino. I’ve been wanting to learn Arduino for a while, and this seems like a great excuse.  There are a lot of great repeater controllers out there already – I am a big fan of the SCOM 7330 – but they’re pricey, and this is ham radio.  We’re supposed to build stuff and experiment!

So, I went to my local Micro Center and grabbed the Inland Uno Learning Kit – it came with a bunch of stuff, but I was mostly interested in the Arduino board, breadboard and jumper wires.

A basic repeater controller only needs to do a few things:

  • Key up the transmit radio when the receive radio is receiving
  • Route the receive audio to the transmit radio
  • Send an ID at least once every ten minutes during a conversation.

And that’s really it.  Sure, you can have more advanced features, like DTMF decoding for functions like turning the repeater on and off, hang timers, courtesy tones, the list goes on.  I am going to start with only the most basic functionality.

To test, I will be using Motorola Maxtrac radios.  They are cheap, readily available, and many have a 16-pin connector on the back that can provide all the connections I’ll need.

Let’s get started.  For Part 1, I will only be connecting a transmit radio – I will use a simple push button for COR input – so I will only need:

For now, the only connections I will be using are:

  • Push-to-Talk output – pulled to ground when the transmitter needs to transmit – Pin 2
  • COR input (which gets pulled to ground when the receive radio is receiving) – Pin 3
  • Morse Code ID Output – Pin 4

That’s it for now.  I will get to audio mixing in a later post – we will eventually need to mix the receive audio in with the morse code ID audio.


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