[Elecraft] 30 Metre Birdy

[Mike Harris]

G'day all,

I don't monitor the list all the time so this might have already come
up.

Following installation of the replacement BFO L33 and realignment of
filters I was casually tuning 30 metres and bumped into an S1
(flickering first LED) signal on 10115.22kHz (my calibration,
currently about -50Hz on 10MHz WWV).

It was interesting to step through the filters and note that signal
vanished out of the passband of each filter and had to be retuned.
Stepping through the filters on a regular CW signal results in
basically zero frequency shift.

Also noticed that the signal step shifted approximately 170Hz lower
by rotating the power control from QRP to QRO with a noticeable
change in signal level, can't remember which was stronger.

The signal is internally generated.

The signal is probably a high order mixing product, 5th order or
higher which will be confirmed when I check the tuning rate later.
The audio frequency changes HF when tuning HF and rapidly vanished out
of the filter and stepping at a significant multiple of the 10Hz
tuning step.

Whilst removing the data lead from the rear of the KPA100 I noticed a
change in audio note and gently squeezing the case results in very
noticeable change in audio frequency, implying that it might be BFO
related.  Are those resistor legs on L33 acting as little BFO antenna?
A high order harmonic of the BFO could explain the shift in signal out
of the passband with filter bandwidth changes and consequential slight
changes in fundamental BFO frequency.

Just in case and to start minimising the possibilities I powered down
the KAT100, no change.  Have yet to remove the KPA100 to eliminate (or
implicate) the processor clock in the equation.

This situation might have existed before I made any changes, however,
given that this signal it is so noticeable with its high speed tuning
step as well as being close to the 10116kHz activity spot I don't
think I would have missed it.

Regards,

Mike VP8NO
#1400