I found the problem.
Turns out that there is a capacitance spec to the BFO crystals. The
original order that Dave Hammond placed was for 32pF crystals, however ICM
suggested that perhaps these have a bit too much capacitance to be able to
be pulled down to the CW frequency. A call to Ten-Tec confirmed that the
BFO crystals are spec'd at 20pF, and so a call to ICM to order a new
9.003300 Mhz Y2 crystal was in order.
I decided to order the new 20pF crystal at 9.003300 rather than 9.003000...
for the same reason that Ten-Tec is probably using this value in the Omni VI
despite what the schematic sez. These crystals are 25 ppm, so it could be
off by as much as 250 Hz. If the 9.003000 crystal is below the stated
frequency then you can't get it set correctly for USB. Having the higher
value prevents tolerances from causing a problem.
I've put back the original 9.003300 Ten-Tec-supplied crystal and adjusted
everything, and will report further once I get the new crystal (for those
who are interested). Yes... the drift problem on transmit is still there
with the old crystal (sigh...). Once I am done I will document the process,
again for those who are interested.
- jgc
John Clifford KD7KGX
Heathkit HW-9 WARC/HFT-9/HM-9
Elecraft K2 #1678 /KSB2/KIO2/KBT2/KAT2/KNB2/KAF2/KPA100
Ten-Tec Omni VI/Opt1
email: kd7kgx@arrl.net
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