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Doppler tracking question



Hello All,

I'm wondering what might be the normal, and perhaps the best, method of 
tracking the transmit frequency.

For receive Doppler tracking I do the following:

Read the receiver frequency from the radio.
Calculate the Doppler shift for that frequency.
Subtract the Doppler shift from the receiver frequency and call this the base 
receiver frequency.
All subsequent Doppler shifts are then added to the base receiver frequency at 
a predetermined time interval.

This seems to work accurately, at least for the time that LEO satellites are 
within view. I still get some drift on AO-40 over a period of say half an 
hour and perhaps that should be expected.

For transmit Doppler tracking I've tried two methods:

Read the transmitter frequency from the radio as above except Doppler shift is 
subtracted where it is added above.

The other method calculates what the transmitter frequency should be based on 
the satellite's transponder's receiver and transmitter frequency ratio.

Neither of these methods seems to be 100% accurate and I'm not sure which 
method I should persist with; the first I think.
  
-- 
Regards,
Phil.


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