[amsat-bb] SatPC32 leading the satellite

Erich Eichmann 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?
> Jim
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