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Re: Further AO-40 MB measurements for FreqHeads

Hello Howard,

Friday, June 21, 2002, 2:05:47 PM, you wrote:

> Further to my previous note, I managed to take predicted and observed MB
> frequency measurements from MA6 to MA128 and plugged them into an Excel
> spreadsheet.

your observations are very interesting and confirm what I suspected
since long, namely that the MB frequency at the satllite is not stable
but depends possibly on the load on the supply voltage.
My observations are based on the experience with my tracking
programme SatPC32 by DK1TB which performs CAT control of my IC-910H
radio. This works very accurate based on a given frequency and adding
or subtracting the doppler shift in accordance with the distance of
the satellite from my location. This is just mathematics and cannot
be wrong (I hope).

However, I noticed that I had to correct the calculated frequency very
often by several Hz up to 2 kHz and I have several times discussed
this with DK1TB. Finally we came to the conclusion that it is the
oscillator at the satellite itself which produces the frequency shift
and what now is confirmed by your scientific research. It would be
nice to compare the frequency shift with voltage parameters from the
telemetry if there is a coincidence.

The conclusion for users of tracking programs with built-in doppler
correction by CAT control is that it will be necessary to perform
frequency corrections manually during the pass.


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