[Elecraft] P3 spurious display

[Craig D. Smith]

To avoid confusion, please note that this posting is not about the recent
0.50 firmware upgrade, but rather behavior with the previous release-level
version.

I'm experiencing some curious behavior from the P3 on CW that perhaps some
of you can help explain.  Certainly not a show-stopper, but sometimes mildly
annoying.

I notice this mainly during contests when I'm using my contest program to
key the K3 via the KEY input.  I see a spurious signal displayed on the P3
that is 800 Hz above my xmit frequency.  At first, I thought this was an
actual signal, but soon realized it was some kind of display artifact from
keying the K3.  It looks like a regular CW signal, and has a maximum
amplitude of about -80 dBm.  It seems to be generated during closures of the
KEY input to the K3.  It appears to be independent of power level or the CW
pitch frequency.  Same result using antenna or dummy load.

This is MUCH less of a problem when using the internal K3 keyer via the
PADDLE inputs.  If I hold down the paddle to generate a string of dits, the
P3 display freezes at the baseline noise level and the spurious indication
does not appear.  On the other hand, if I generate a series of dits with the
paddle by making a sequence of rapid contact closures of the dit paddle, the
spurious P3 indication does appear.

In other words, it appears to have something to do with how the K3/P3
handles the "freezing" of the P3 display during CW transmit, especially in
the event of rapid keying contact closures.

Any ideas?

Thanks and 73      Craig   AC0DS