> So, where is the TCXO adjustment? Maybe two possibilities:
> the "shiny" silvery gadget with a hole in the top \
The TCXO adjustment is the metal can with the adjustment screw
visible through the hole on assembly A10. Either the can or PC
board next to it (I forget which) is screened with a 44.55 Mhz
marking. I used a small blade ceramic screwdriver. There's not
much "vernier" to the adjustment, so you need a little "touch" to get
it right.
The MixW/DIgipan approach may be more precise ... but I suspect
you'll get as close as it's worth getting with my quick and dirty
method (beating the cal signal audibly against the SPOT tone in
either LCW/UCW). In any case, once stable, the TCXO wanders a
couple of Hz or so around the adjustment point over time, so there's
just so much pin-point precision that's worth the trouble.
Let the radio warm up for at least 4 hours with the bottom cover in
place before you make the adjustment. I took some long term
measurements and found it took about that much time for the
TCXO/radio in my shack's environment to reach thermal stability.
Grant/NQ5T
PS. The last time I posted about measuring the warmup drift
pattern, there was much gnashing of teeth (and interesting lectures
on variable proagation delays, etc.) about how measuring against
WWV would introduce all kinds of errors, etc. and was probably
causing the pattern I was seeing. I've since used the now
ubiquitous z3801a, and found the same warmup drift pattern I found
when using WWV. FWIW ....
|