On 12/17/2023 12:05 PM, Jim Murray via Elecraft wrote:
My thought is at this point the P3 is not doing me much good looking
for a weak dx signal. I have to think I have something not set up right
etc..
What is required is careful (and ongoing) adjustment of P3 controls. For
everyday operation, I set the display range to 32 dB, set Averaging to
max (20), and adjust the noise floor to the bottom of the display. The
first two adjustments are more or less set and forget; the noise floor
will change from day to day and from band to band. On CW and RTTY, I
typically use display widths of 50 to 100 kHz, or whatever covers the
activity; on SSB, I usually set it to the 200 kHz max. In both cases,
setting the center so that I'm seeing that activity.
What Averaging does is cause random noise to cancel, but causing signals
to be reinforced. Averaging is the power tool that lets us see weak
signals. Averaging also emphasizes electronic noise, that's acting like
miniature radio transmitters. It's also important to set the P3 so that
the frequency limits of the display remain fixed as we tune the band; if
we set it to always be centered, averaging will re-start as we tune,
rendering it useless.
If I'm going for very weak signals on a quiet band, I'll change that 32
dB display range to 24 dB; in a contest, with lots of big signals, to 42
dB.
I do NOT recommend averaging of the waterfall itself.
These applications notes on different topics include P3 and P3/SVGA
screen grabs. The first two are "on-the-air;" the third was done in my
shack, looking at the bandwidth of various rigs and amps. If you know
what you're doing, the P3 and P3/SVGA are very good test instruments,
that are with respect to frequency resolution, far superior to HP
spectrum analyzers!
http://k9yc.com/K6XXAmpTalk.pdf
http://k9yc.com/KillingReceiveNoise.pdf
http://k9yc.com/P3_Spectrum_Measurements.pdf
73, Jim K9YC
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