The best way is to FSK the transmitter. This will require you to interface
the main osc, or PLL if used. To receive the FSK signal you will need to
access one of the IF stages. I don't recommend this unless you have a strong
RF background.

Actually, using a Two-Way radio for telemetry is very easy. You can send
data through the microphone and receive it through the speaker. The data
rate is a little slow however.  Output one pin of the pic into a circuit
that will convert a square wave audio to sine wave, then attenuate the
signal to the microphone audio level. generate a 1000hz tone for a logic
level zero, and a 2000hz tone for a logic level one. Another simple circuit
in the receive to convert the sine wave to a square wave , and measure the
frequency being received.  Some what simple but it does work.

Gordon Varney



> How do you connect a pic to a two way radio? Do you need a
> interface between
> the analog input (microphone) of the radio and the pic(Tx) and again from
> the speaker to the pic(Rx).
>

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