United States Air Force Military Affiliate Radio System
"Providing the reins of command in emergencies"
AFF1N's Audio Interface
T1 and T2 are 8 ohm to 1K ohm (Radio Shack PN 273-1380)
This is an inexpensive interface between the computer and tranceiver. There are a number
of methods for interfacing with the transceiver. The microphone and headset sockets will
work for all of the transceivers. Most all newer transceivers have mic input, audio out and
PTT all in the microphone socket. And, most all newer transceivers have an auxillary in/out
(ACC) on the back panel. The drawback of the ACC is controlling the audio out; it's usually
a fixed level output.
This interface can be used for all of the soundcard digital mode software, such as MixW, etc,
as well as broadcasting the MMTS's. The MMTS's are in .wav files on the
computer hard drive. I eventually used a small plastic "hobby box" to mount the components
after trying a metal box. The input/output points are RCA jacks which I found have to be
isolated one from the other, thus the plastic box; all of the leads are shielded wire. As a
side note, it is possible to record .wav files from the transceiver, too. The computer
soundcard control is used to vary the input and output levels. I use a small mixer in my
application, though, and found that it is easier to control the levels with the mixer.
After building the initial, single rig interface, I decided to see if I could construct an
interface that would support both rigs for simulcasting and/or switching back and forth for
multi-frequency operation. This means one microphone and feeding the output of the computer
to either or both rigs at the same time.
Click Here to see the schematic.
