On Mon, 26 Mar 2012 19:57:32 -0700
"Robin" <wb6tza@socal.rr.com> wrote:
> Maybe this is a good time to share the techniques we
>individually find successful for
> hearing through the giant sparks.
>
Here are my experiences from TX3A (and other low-band
DXpeditions). On TX3A, for 30 nights in a row, 8 hours
each, I had the challenge of copying weak signals through
strong, incessant lightning crashes (especially from
sunset until about 10:30 local time). With the following
set up, this is what I found to work best:
Local Set-Up and Conditions: Receiver K3, ANT DHDL (-36
dBi Gain), No local RF noise, Bose noise cancelling
headphones (strong local acoustic noise from birds):
I set the AGC to Fast, mostly used the RF gain to control
levels, and set the IF Filter to 600 Hz. This last one may
sound counterintuitive, but I have found that: a) setting
the filter too narrow results in ringing which stretches
out the effects of a lightening crash, masking more of the
signal, b) setting the K3's DSP filter narrower changes
the shape of the CW pulses and makes them stand-out less,
and, c) somehow the narrower filter settings degrade the
"understandability" of weak signals. (This last one was
also confirmed by my DXpedition partner, Tomi, HA7RY, who
has better ears and can copy CW great.)
One more thing, with the above settings and with weak
signals, it was absolutely essential to be able to totally
concentrate during the crucial seconds when copying a
call. I found that allowing any thoughts to intrude would
wipe a call. Usually, with strong signals, you don't need
total concentration to work without errors. You can think
of other things, such as: should I change the RX
settings?, should I try the other antenna?, shift in the
chair as my butt is getting sore, etc. But with really
weak signals, any intruding thought would create internal
"noise" that could cause me to miss a call. I believe that
learning to concentrate, and to be able to switch off all
thoughts for a few crucial moments, is as important as any
DSP filter or or other signal processing "hardware".
I hope this helps,
George, AA7JV
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