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Re: R: AO-40: Rcv



At 02:16 PM 5/18/2001 +0200, i8cvs wrote:
>Les
>For satellite work it is a good practice to keep the receiver frequency
>constant and compensate for Doppler
>using the VFO of  our transmitter.

No, that's wrong. If you must tune only one radio, you should always tune 
the one with the higher frequency, which is the receiver in this case. It's 
better practice to tune both. See 
http://www.amsat.org/amsat/features/one_true_rule.html for a longer discussion.

However, I find that my downconverter, at least, is not stable enough for 
this to work. Its drift is often greater than the Doppler shift! So the 
only practical scheme (until I get a stable downconverter) is to tune only 
the receiver, the reverse of what you suggest. I suspect many other 
operators are in the same situation, with the cheap downconverters (which 
were intended for broadband services and so were not designed to be 
especially stable) being so popular.

>Using this procedure each partecipant in  a QSO will stay in the same
>frequency all the time for the benefit of the others instead to ride up and
>down  tuning the band.

Not really. What you say is only true if you ignore the differences in 
Doppler on the downlink between different stations.

73  -Paul
kb5mu@amsat.org

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