[time-nuts] Frequency Measuring Test Results
John Ackermann N8UR
jra at febo.com
Fri Jan 21 21:29:08 UTC 2005
The results of the 2004 ARRL Frequency Measuring Test are out. This
year, they provided the nominal carrier frequency and asked for reports
of the audio tone (in SSB, suppressed carrier mode). That actually made
the test less challenging because we were constrained by the accuracy of
the announced carrier frequencies, which weren't given with the
precision one might like -- they only announced to the nearest kHz, so
our math had to start from that round number.
Here are the official frequencies and what I measured:
ARRL N8UR
80M 1105.02Hz 1105.013Hz
40M 1108.26Hz 1108.279Hz
20M 1116.77Hz ----
According to their averaging, that puts me +0.01Hz on 80, and -0.02Hz on
40. I'm surprised 40 came out that well given the horrible conditions
on that band; we could barely hear the signal. I heard nothing at all
on 20M.
The same audio tone was used to feed all the transmitters, so you can
see the frequency difference between them -- a 9.75Hz spread between the
80M and 20M units.
Once again, I used a Linux spectrum analysis program (Baudline --
http://www.baudline.org) to measure the delta between the audio note of
the unknown signal and the audio note of a local signal generator that
was steered to within 50Hz or so of the unknown. Baudline provides
frequency resolution down to milliHertz, so is a good tool for this job.
I have a web page (not updated yet with the official results) that
describes the setup and has a few screenshots at
http://www.febo.com/time-freq/fmt/fmt2004.html
John
More information about the Time-nuts_lists.febo.com
mailing list