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AO-40 Beacon Frequency Measurement for FreqHeads



Folks

I've put up a spreadsheet at
http://www.g6lvb.com/images/AO40doppler0206180500.zip which has twenty
minutes or so of MB frequency measurement from MA229 to MA233, comparing
predicted frequency to actual frequency.

Working back, these were the freqencies at the satellite to generate a
1000Hz center frequency on a USB receiver back on Earth:

Average 2401.328142MHz
Min	  2401.328109MHz
Max	  2401.328161MHz

Of course, to zero beat, add 1000Hz to the above frequencies.

As can be seen the variation is minimal and probably at least +/-10Hz of
this can be put down to AO40Rcv's freqeuncy stepping feedback loop.

The receiver is an AR-5000 in USB with a rubidium frequency source accurate
to about 0.001ppm. The receiver feeds an unmodified AO40Rcv V1.40 which is
set to centre at 1000Hz.

The AR-5000 has is stepped in 10Hz steps by the AO40Rcv software to correct
for Doppler.

A sample of predicted/actual is taken every second, together with the
computer clock which is acccurate to within one second.

The Keps used were current as at 16 June 2002.

Nova is used as the prediction software, which visually is within about 10Hz
of the predictions of InstantTrack and Wisp/WispDDE.

Nova's DDE Range Rate and the AR-5000 receiver frequency are fed into a
piece of homebrew software in real time and a file is generated.

I've taken the file generated and produced the spreadsheet.

I'll also re-run the excercise over different parts of the orbit.

73 Howard G6LVB


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