Hi Julius,
If the birdie at 28.019/20 MHz changes frequency when you change the
transmitter power demand from <10w to >10w, then the KPA100's HV Bias
oscillator is involved. Vic, K2VCO, and I had an off list discussion some
time ago about birdies including this one, and though Vic found the birdie I
did not because his HV Bias oscillator runs at 18.434 MHz while I have opted
to keep mine at 16.293 MHz for reasons other than birdies. If I remember
correctly this particular birdie involves not only the HV Bias oscillator
but also another oscillator in the K2 which mix to produce a signal at a
spurious response frequency of the receiver when tuned to 28.019 MHz. I'll
have to look up my notes.
You can move this 10m birdie to another frequency by changing the HV Bias
oscillator frequency although the options for all band freedom from birdies
involving this source are limited. In my K2/100 the bias oscillator signal
enters the K2 via the ribbon cable, which can be 'choked' with a clamp on
ferrite, and the loudspeaker leads which can be removed from the KPA100
board where the trace acts as a link, but be advised that these last two
mods might not work with all K2/100s. Later on I repackaged the HV Bias
oscillator and voltage multiplier in a shielded box, with pi configuration
filters on all DC lines to kill the problem at source.
73,
Geoff
GM4ESD
----- Original Message -----
From: "J F" <[EMAIL PROTECTED]>
To: <elecraft@mailman.qth.net>
Sent: Tuesday, December 19, 2006 1:21 PM
Subject: [Elecraft] 10M birdie and other assundries
Just out of curiousity, after spending some time on
10M during ARRL 10, I noticed a birdie around
28.019/20. Is there a way to eliminate this or move it
below 28.000?
<snip>
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