> TC stands for Temperature Compensated, NOT Temperature Controlled. So
> the oscillator controls should be responding to its environment.
(Not sure why the apparent presumption that the I didn't know the difference.)
The
time required to reach thermal stability (of the TCXO) is longer than one might
expect
from the "let the radio warm up for an hour before calibration" rule of thumb.
That
was my ONLY point in the original posting.
> But HF propagation causes short term variations in frequency of about
> 1 part per million, 20 HZ at 20 MHz WWV so the measurements may not be
> of the TCXO but likely are of propagation changes.
Certainly there is an effect. But the drift pattern from cold start is the
same every
time. Unlikely to be the result of propagation changes, unless my Orion
effects some
hitherto unknown principle of repeatable action at a distance :-) I can't
tell you how
accurate the absolute frequency is (given all of the variables, etc.), but I
can tell that
the drift pattern from cold start is not repeated after the radio becomes
thermally
stable.
> Frequency
> measurement specialists expect it to take a month of averaging HF WWV
> signals
Most hams turn on the calibrator (probably roughly checked a year ago with WWV
at
10 Mhz), zero beat the calibrator signal, move the fudicial hairline, find a
clear spot
and call CQ. Moving the fudicial is all this "simple calibration method" does.
It's the
same "simple" method described in most manuals of most synthesized radios I've
owned that offered a "calibration" control of some sort. It gets the virtual
hairline
lined up in about the right spot. It (or I) never presumed that the method
somehow
achieved frequency measurement or calibration immortality ...
Life was simpler (and less contentious) when all radio dials had thick
pointers :-)
Grant/NQ5T
|