I am a bit mystified by some observed behavior in my SO2R RTTY setup.
I feed the left radio into the left audio channel, and feed the right radio
into the right audio channel.
I have one MMTTY and one 2Tone per radio, each set up to only look at the
appropriate left or right audio channel.
Doing this all in SO2R seems to work. But every so often a really loud
signal on radio 1, will be decoded and printed in the decoder for radio 2,
especially if the signal on radio 1 is pinning the S-meter and radio 2 is
looking at a signal in the noise. Same things happen with 1 and 2 reverse.
The first time this happened I was stumped, but then figured out that I had
left a microphone plugged in to the sound card at same time. Audio was
escaping from my headphone, finding its way to the microphone, and then
being fed into both channels! (Evidently microphones are treated as mono
devices.)
But now I have the microphone unplugged, and still the leakage is still
continuing at a lower level. I don't see any signs of decoder leakage in
the decoders' waterfalls when just looking at band noise and regular
signals but we all know in a contest there are some really loud signals.
I'm trying to figure out if this "leakage" between channels is in my PC
hardware, in the audio cabling, or in the windows driver, maybe a
microphonic effect in the PC case, or some common coupling through ground
or a power supply, or what. Or maybe there is some AGC function being
applied by the sound card ADC in response to a loud signal, such that a
loud signal on one channel shows up very weakly in the other channel. Any
advice on tracking this down?
Tim N3QE
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