My UN-answered question

I have been "dreaming" about this for a couple years now,
but can't seem to get a real answer to my question(s)

I have asked this question on any number of Raspberry pi
forums,but no one seems to understand what I want to do.

I have the two Pi's on my home network for weeks at a time,
and I ssh one to the other with no problem, so I am reasonably sure this can be done. ( currently up time of 22 days)

To my thinking this should be easy,
but I am not a programmer of any sort.

I would like to remote control a radio ( Amateur radio)
using two Raspberry Pi's.
I have most of what I think I need for this project.
2 Raspberry Pi's
2 USB audio dongles
a two relay board for radio interface.

My theory, the pi's would talk to each other via the internet.
when I "ground" a GPIO pin on the "local" pi, the same pin
on the "remote" pi is "grounded", this in turn operates a relay
which keys the radio. I know to do this "correctly" I need to go through some sort of a timing circuit, so if I loose "control"
the transmitter will "UN-key".
As well as keying the radio, I need to do something similar
to control frequency ( using a different GPIO)

PART two : I need to pass full duplex audio between the two Pi's, the audio will actually only be going one way at a time, but I think it will be easier to make the link full duplex, so as not to have to worry about audio switching.

I am looking forward to anybodies suggestions.

Thanks
Don Ritchie, K8ZGW ( Twinsburg Ohio)

There are several members that are Hams including me so hopefully you will get a few ideas.

What radio are you planning to use for your project and does it have a CAT interface? As suggested in the link below using a remote desktop application to control the radio functions and some type of VOIP software to transmit the audio would be the easiest solution. Your part two is not easy especially since your not a programmer. You need to digitize the audio, compress, put it into packets and then reverse the process on the other end.

You will need some type of circuit to interface the audio output of the Pi to mic input. Many modern digital radios have built in USB sound device which makes interfacing to a computer fairly easy.

https://www.dxzone.com/how-to-remote-your-radio/

Thanks for the reply,

Sorry I didn't get into the radio interface.
The radio ( at least for now ) is an old GE Master II.
The radio interface I have all but figured out.
It is a two channel, commercial radio, (6 meters 50 watts)
what I need out of the Pi;

Two way audio: ( as you said, the hard part)

Change of state on two different GPIO pins
There are two relays, the first will be the PTT, and will need to be
run through a timing circuit ( keep alive) in the event there
is an internet interruption.
The other will be a F1, F2 choice.( F1, relay non operated - F2, Relay Operated)
Again, the same "keep alive" used in the PTT should be "forked" to the channel select relay.
as I need it to be in F! "at rest". ( F2 is a regional weather repeater ).

I currently have the Pi's running on my home network, headless.
I can SSH into both from my Win 10 machine and my Mint 18.3 machine
In my "everyday testing" I SSH from "local" pi into "remote Pi" (actually less then a foot apart)
and ping local from remote (.250 Ms) so it looks as though SSH will work.

Thanks,
Don

As you may have guessed, I have seen about every link there is on the internet,
and none of them are applicable to my needs.
There are are commercial devices on the market,
but WAY out of the average Hams price range. ( $300 - $500 per end)

Thanks,
Don

There are many ways.

You can find a few guides on connecting relays and switches to the Pi with python probably being the easiest language for writing a program. You can create a simple server using xinetd to respond to commands and activate the relays on the other end with ssh being used as the secure tunnel. Its possible to send direct commands via ssh although for command/control maybe not the best method.

As stated audio is the hard part. mumble might be the easiest to implement.

https://hackaday.com/2016/09/07/rasp...es-to-friends/

You still need a circuit to interface between the audio output of the Pi and the mic input of the radio.