Beth,
If the bandpass previously was tuned properly and the behavior is as you
stated, check the VCO frequency at TP1. Compare the frequency obtained
with the internal counter probe with the chart on the Schematic Key
sheet in the manual.
If the frequency of the VCO is not correct, you can obtain RF out of the
mixer and buffer stages, but when it gets to the bandpass filter, the
filter will 'swallow it up'.
You can also use the counter probe to check the frequency at other
places in the K2 other than the Test Points designated - you may have to
invent some kind of short attachment device, but it should work - the
counter itself shoud be good up to 40 MHz.
73,
Don W3FPR
Beth Wenzel wrote:
Thanks for the tip Lee, it got me to looking at the TX mixer / buffer part of
the chain. The ALC / BFO line into the mixer is consistent across bands,
(however the micro controller quickly drives the ALC to max at 28 mhz). The
mixer output looks ok, as well as the output on pin 6 of the buffer. However
when I measure of the cathode end of D6 the relative output is down, as if the
bandpass filter is sinking the energy.
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