[amsat-bb] Re: AO-7 help

Glen Zook gzook at yahoo.com
Sat Sep 26 08:09:05 PDT 2009

I haven't used AO-7 for some time (need to revise my antennas to do so again).  But, back in the "goode olde dayes" (when the satellite first went into orbit) we didn't have any problems with Doppler.  The accepted method was to leave the transmit frequency alone and keep one hand on the receiver to compensate for the frequency shift and send CW with the other hand (or hold the microphone for SSB).  No one even thought of compensating for Doppler any other way.

Of course at the time everyone used a separate receiver and transmitter (no transceivers) so you could keep the receiver active while transmitting.  There were hundreds of QSOs made on each orbit and everyone had a "ball".

Glen, K9STH
AMSAT 239 / LM 463

Website:  http://k9sth.com

--- On Sat, 9/26/09, Andrew Glasbrenner <glasbrenner at mindspring.com> wrote:

Those splits are only right when Doppler is zero. Other wise, you have around +/-7 khz shift to deal with. It's really tough to work AO-7  half-duplex with no Doppler tuning. REALLY tough. If you have a PC nearby, I'd recommend trying to use SatPC32 to control the Doppler shift during the pass. CAT cables are pretty cheap on Ebay, and really easy to set up with the 897.
Also, since you are using gain antennas AND are half duplex, you should make sure you keep the power output low, like 5 watts or so, since you can't hear if you our overdriving the uplink and making the satellite FM for everyone.


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