[amsat-bb] SatPC32 leading the satellite
erich.eichmann at t-online.de
Fri Jul 1 06:28:09 UTC 2016
There are the following options in menu "Rotor Setup" they could have
used to update the azimuth and elevation antenna positions:
a. in time increments, say 3 seconds or less.
b. when the satellite's position (azimuth or elevation) changed by a
certain CONSTANT amount of degrees (dead band), say 3 degrees (their
setting) or less.
The program then updates both antennas every 3 seconds or whenever the
azimuth or elevation changed by fix 3 or more degrees. Then It positons
the antennas a half step in front of the current satellite position.
So, the satellite will run through the "focus" of the antenna.
There is a sub option of b. (which they used): "gain releated". When
the elevation increases the azimuth position of the satellite changes
very quickly and the azimuth antenna positon will be updated very
often. On the other hand the horizontal opening angle of the antenna
becomes virtually wider, following a cosine function (at 90 degs
elevation azimuth is meaningless). The feature utilizes this effect to
reduce the number of horizontal updates without loss of gain. Also, the
signal is stronger at high elevation angles, due to the smaller distance
of the satellite. So, with a small update step they should not loose
data, even with the setting "gain related".
That all is described in the manual (menus "Rotor" and "Rotor Setup").
73s, Erich, DK1TB
Am 01.07.2016 um 03:55 schrieb Jim White:
> I was at a university ground station today and noted their antennas
> were not keeping up with their satellite on a high elevation pass.
> They are using SatPC32 with the G5500 rotor. They have the dead band
> set to 3 degrees. Since they are using a pair of long UHF Yagis for a
> total of 21dB gain there were some lost packets for about 2 minutes or
> so around TCA. Their sat was deployed from the ISS so is currently at
> about 400km altitude which means it's zipping by rather quickly when
> the elevation is above about 75 degrees or so.
> In the past I've used tracking programs that allowed a 'lead'
> setting. That is, you could tell the software to lead the satellite
> by a few seconds. That did a pretty good job keeping the sat in the
> beam width when the AZ was changing quickly. I'm not finding that
> setting in SatPC32. Is there one, or another setting to accomplish
> the same thing?
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