[Elecraft] P3 - What am I observing?

[Phil Westover]

My K3 and P3 are connected in the usual way (RS-232, etc.)

My K3 has a 500Hz roofing filter, and I typically set my DSP filter to 500
Hz when operating CW.

Using tonight's display, I have an approx. -150dB average noise floor on 10
meters.  I'm not exactly sure how to identify the "noise floor" using the
P3, but the display (without considering signals) basically averages across
the -150dB graticule.

I have the P3's span set to -1kHz to +1kHz, making each horizontal division
500 Hz.

Upon checking in to my nightly 10 meter net on 28.130, I see the net control
operator's signal peak at about -100dB.

Here's my question:  What are the two "spikes" that I see about 500 Hz to
each side of 28.130, approximately 25-30 dB down from the center's peak
level (-125 to -130 dB)?  These spikes are above my observed floor about
20-25 dB.

It's a beautiful thing; I simply am not sure what I'm seeing.  One thing I
am sure of, when you all respond with the answer, I'll bop myself in the
head for not thinking about it!

Actually, I'm thinking that there is a great opportunity for someone of
knowledge to write a tutorial that goes beyond the owner's manual in
explaining the types of things we can see with the P3.

Another one, for instance, would be, "When I use the CWT control on the K3,
why does my P3 almost always shows that the zero beat frequency is about
20-30 Hz off?" If I use Marker A to center over the observed signal's peak
and trigger the P3 to move the K3's VFO to that peak, my little CWT visual
indicator on the K3 shows me to be "off" by a couple of clicks.  What is
that telling me? 

Anyway, I sure would like to use the P3 to learn more about scans that I'm
observing and how my K3/P3 combination is processing them!

73,
Phil  WA7URV 

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