[amsat-bb] Re: PC clock
erich.eichmann at t-online.de
Wed May 12 01:50:27 PDT 2010
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
73s, Erich, DK1TB
----- Original Message -----
From: "Mark L. Hammond" <marklhammond at gmail.com>
To: "i8cvs" <domenico.i8cvs at tin.it>
Cc: "AMSAT-BB" <amsat-bb at amsat.org>; <W7IN at montana.com>
Sent: Tuesday, May 11, 2010 10:25 PM
Subject: [amsat-bb] Re: PC clock
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.
On Tue, May 11, 2010 at 4:07 PM, i8cvs <domenico.i8cvs at tin.it> wrote:
> ----- Original Message -----
> From: "Greg D." <ko6th_greg at hotmail.com>
> To: <w7in at montana.com>
> Cc: <amsat-bb at amsat.org>
> 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
> 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
> antennas are finally there then the satellite is already in another
> far advanced in it's orbital path particularly when the satellite pass is
> I dont think you want to run the motors every 5 or 10 seconds othervise
> control relays will work as a machine-gun
> So the issue is not on clock accuracy or Keps or mathematics behind them
> it is on the tracking system that we normally use to mimichaise the
> satellite position with a phase difference between the satellite
> 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
> that your antenna pointing is always a little bit behind the ISS position
> 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
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Mark L. Hammond [N8MH]
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