Hi,
After adjusting my TCXO tuning a few days ago,
I decided to track it for a several hours. Turned the
rig on at 7:20 AM Monday morning, room temperature was
74 F. Used MixW to monitor the delta from 1000 Hz beat
tone against WWVH about 11 miles West from my QTH,
Orion tuned to 10001.000, LSB to create the beat trace
on the waterfall display. Placed the cursor at the trace.
Perfect match would cause a reading of 1000.0
Time Frequency Read
7:20AM.........983.5 Hz
7:23..............963 (!)...Rapidly falling?
7:24..............959.5
7:25..............955.8
7:26..............953.7....The evident low point after turn on.
7:27..............954.3
Got another cup of coffee
7:29..............965.5.....Increasing rapidly
7:30..............976.8
7:31..............985.0
7:32..............988.7
7:33..............989.0.....Settled?
7:34..............988.6
7:35..............987.4.....Changing very slowly
Let more time pass as the increase is very slow
8:20..............987.3.....About an hour after turn on, seems settled
8:40..............988.3
9:00..............988.4
10:25............987.1
11:08............987.3
11:25............987.9.....Room temperature up to 81 F
Stayed here the rest of the day.
This morning, Tuesday, repeated the process, starting
at 7 AM, same room temp. or 74 F. And just about
the same results. Except within the first 9 minutes the
frequency match dropped from 979 at turn on, all the
way down to 944. By 7:10, the climb back up had begun
reaching 987.6 at 7:53 AM. There it has remained,
essentially steady these last four hours. Or roughly
12 Hz low from WWVH both days after warm up.
This makes no differences at all when comparing a tuned
signal simultaneously with both the Orion and the RX-340.
Of course, a very slight beat note can be detected on
CW, if you listen closely. But no delta at all in fidelity,
etc. using SSB and listening to the same signal. BTW,
the 340 is locked to the GPS as an external frequency
standard, so I assume it is smack on! Listening to
WWVH with the two together on AM, no way can you
hear a difference.
Repeated the test at the other WWVH signals, results:
20 MHz............986, 14 Hz low
15 MHz............986.6, 13.4 Hz low
5 MHz..............987.9, 12.1 Hz low
2.5 MHz...........988.4, 11.6 Hz low, and here the MixW signal
was rock steady. At higher frequencies, there was always
a few 10ths second "dither" or randomness to the delta from
WWVH. I am sure the 2.5 MHz signal is ground wave from
the single vertical dipole used at WWVH on 2.5, the
others are probably back scatter, as the antennas arrays
out there are "beamed" to the West, just exactly away
from my QTH. They use vertical arrays out there, see
for example these photos of WWVH here on Kauai:
http://www.boulder.nist.gov/timefreq/stations/wwvhtour.html
I intend to leave the Orion TCXO as it is for now. Will see
where it is in six or eight months; they are supposed to
"settle in" over time after new. Has been interesting to
both adjust and measure, hi.
73, Jim KH7M
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