Dear Markus, John, LF Group,
At 08:57 13/12/2002 -0500, you wrote:
>- I am usually avoiding the AGC automatic gain setting as it makes it
impossible to distinguish between reduced signal and increased noise.
Sometimes when dashes are disrupted to a pair of dots, it would help to see
whether there is a burst of QRN in the middle.<
I have used it to make things less touchy with my local noise levels, which
are both considerable and variable
If you recall the "Hendrixizer" from some time ago, the same effect works
well with QRSS. If you crank the RX gain up until the audio out is heavily
clipped, it does quite a good job of reducing the effect of QRN crashes.
The other effect is that, because you are effectively limiting the noise
amplitude, the output noise level is fairly independent of the actual
amplitude of the noise at the input. This makes the display quite tolerant
to gradual changes of noise level.
Try it - you might be surprised! On my RX, I just switch off the AGC and
turn AF and RF gain to maximum, and set the sound card gain so it is well
below overload - it sounds horrible, but the vertical streaks largely
dissapear. Of course, it will only work if there are no strong signals
above the noise within the RX passband; if there are, you will get FM-like
quieting, where the strong signal suppresses the noise and weak signals. It
won't help much either if there is strong noise drifting rapidly in and out
of the passband, but then AGC will be just as bad.
I will run a Jason mode beacon on 137.500kHz tonight, over at least 2300 -
0200 utc - any reports will be welcome.
Cheers, Jim Moritz
73 de M0BMU
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