[TenTec] Some Observations on Orion Stability/Calibration

[Grant Youngman]

> 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