Hello Domenico, The very excellent SatPC32 program "leads" so as to keep an accurate pointing at a satellite. It has several adjustments for how often the rotors are updated, gain consideration of the antennas in use, etc.
73, Mark N8MH On Tue, May 11, 2010 at 4:07 PM, i8cvs <[email protected]> wrote: > ----- Original Message ----- > From: "Greg D." <[email protected]> > To: <[email protected]> > Cc: <[email protected]> > Sent: Tuesday, May 11, 2010 7:47 AM > Subject: [amsat-bb] Re: PC clock >> >> Hi Larry, >> >> Ok, I understand the need for an accurate clock, though I believe you're >> expectations for being able to track an overhead pass is pushing the >> limits of orbital prediction pretty hard. Another ham I know locally >> tried this, and ultimately gave up. His issue was not one of clock >> accuracy, but of Keps and the mathematics behind them. >> >> >> Greg KO6TH >> > Hi Greg, KO6TH > > When the software calculate the Az and the El of the satellite at the right > time with an accurate clock then it send a command to the rotators but the > antennas takes a certain time to go in that calculated position and when the > antennas are finally there then the satellite is already in another position > far advanced in it's orbital path particularly when the satellite pass is > overhead. > > I dont think you want to run the motors every 5 or 10 seconds othervise your > control relays will work as a machine-gun > > So the issue is not on clock accuracy or Keps or mathematics behind them but > it is on the tracking system that we normally use to mimichaise the > satellite position with a phase difference between the satellite calculated > position and the actual antenna position when the traching command is sent > to the motors. > > If you go over the roof and you follow the ISS by naked eye you will realize > that your antenna pointing is always a little bit behind the ISS position in > the sky and so a very accurate clock to track a LEO satellite is meaning > less particularly using high gain antennas with a narrow main lobe. > > 73" de > > i8CVS Domenico > > > > _______________________________________________ > Sent via [email protected]. Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > -- Mark L. Hammond [N8MH] _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
