[Elecraft] P3

[Jim Brown]

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