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Precaution using PSK31 on AO-10



To anyone using mode PSK31:

    Check your audio out from your sound card going to the mic input to your
uplink rig
to make sure that you are not mixing in your downlink signal. With the
program and
OS I am running(WinPSKse/NT4.0) does not disable the AUX input on the sound
card when transmitting. This is not a problem with HF but is with (full
duplex) satellite
modes. So far the only way I found to work around this problem is to disable
the AUX input
in the sound control before transmitting and reenabling it when going to
receive
mode. I imagine just turning down the volume on the downlink rig shoud have
the
same results. Or if you are using the microphone method, just hit the off
switch on
the mic (if there is one).
If the station you are receiving is having this problem you will see what
looks like IMD in the
waterfall but the IMD is only on one side of the receiving signal, which is
actually his
downlink being retransmitted just a little off frequency. The farther apart
he is between
his uplink and downlink, the farther that what looks like one sided IMD will
be from his
signal in the waterfall.  Today was the first time seeing a waterfall like
this. At first I was
scratching my head til about an hour after the PSK31 QSO when I realized
what I was looking at.

Good Luck trying out this mode. It does work on AO-10 except when near
perigee when
the AFC in the PSK program could not keep up with increased doppler shift
rate.

73
Happy Holiday's
Tom / N7HXP

mjrtom@home.com



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