Radio Interface
Last Updated: 1/4/2000
This is an interface that I built to perform several different radio interface functions. The interface performs well for my purposes but I cannot guarantee that it will work for other radios or applications. I have listed some applications below.
I used 1/8" mono phone jacks for the audio connections to allow for quick reconfiguration. I used coaxial DC power jacks for the PTT connections to prevent accidental transmissions. My earlier version of the interface had phone jacks for the PTT but I found that while plugging in the connections, the two PTT lines were shorted causing the radio to transmit. The switch (S1) also prevents accidental transmissions.
While I prefers to have my devices isolated, I found that my Kenwood TM-G707's squelch output did not provide enough current to trigger the opto-isolator. I added the non-isolated input for the Kenwood. Because both the isolated and non-isolated circuits operate in open collector mode they do not interfere with each other. Also other opto-isolators will work in this circuit, just make sure to use one with a high enough current transfer ratio. The one I used had a 100% transfer ratio.
PSK31 / Morse Code Interface
This uses my computer and ICOM 746 to transmit and receive audio signals using the sound card to create and decode the transmissions. The configuration is good for PSK31 and morse code programs.
Audio In - Connected to computer sound card Line In.
Audio Out - Connected to computer sound card Line Out.
RS-232 Input - Connected to computer serial port RTS.
TX Audio - Connected to IC-746 TNC 9600 packet data transmit.
RX Audio - Connected to IC-746 TNC 9600 packet data receive.
PTT - Connected to IC-746 TNC PTT.
Sound Card Interface
This uses the audio input section only to feed audio from my ICOM R-8500 to the computer so that I can use programs that utilize the sound card such as WACARS, etc. In this configuration the interface provides easy connections and isolation only.
Audio In - Connected to computer sound card Line In.
RX Audio - Connected to R8500 audio out.
Crossband Repeater
This uses my Kenwood TM-G707 and ICOM IC-746 for crossband repeating to local repeater from my ICOM W32A while I'm around the house.
Audio Out - Connected to TM-G707 TNC 9600 packet data receive.
0-5V Input - Connected to TM-G707 TNC squelch output.
TX Audio - Connected to IC-746 TNC 9600 packet data transmit.
PTT - Connected to IC-746 TNC PTT.