Hi Herich, DK1TB When manually tracking a LEO satellite beginning from OSCAR-6 I realized the same trick to point the antennas with an angle 5 to 10 degree in front of the satellite position.
The same technique is used by hunters to shoot down birds. 73" de i8CVS Domenico ----- Original Message ----- From: "Erich Eichmann" <[email protected]> To: "Mark L. Hammond" <[email protected]> Cc: <[email protected]> Sent: Wednesday, May 12, 2010 10:50 AM Subject: [amsat-bb] Re: PC clock > Hello Mark, Domenico and others, > when SatPC32 updates the antenna positions it turns the antennas a half step > in front of the satellites position. The manual says: > > "Under all tracking options, the rotors are activated with a precession of > one half step, either one half of the time interval or one half of the > tracking angle, to ensure that the satellite moves through the antenna > focus." > > 73s, Erich, DK1TB > > ----- Original Message ----- > From: "Mark L. Hammond" <[email protected]> > To: "i8cvs" <[email protected]> > Cc: "AMSAT-BB" <[email protected]>; <[email protected]> > Sent: Tuesday, May 11, 2010 10:25 PM > Subject: [amsat-bb] Re: PC clock > > > 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 > > > _______________________________________________ > 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 _______________________________________________ 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
