Has anyone else noticed that the USALS algorithms being used in both the vdr-rotor plugin and MythTV aren't accurate for moderate distances away from south (or north)? Has anyone else tried to get the real algorithm from STAB? I've e-mailed them a few times and they seem reluctant to release the algorithm - they have a good system, but it's pretty f'in useless without the correct algorithm. What exactly are they trying to protect? I haven't worked out all the trig in the formula being used in vdr or myth, but it generates almost identical numbers (the differences are in the thousandths of degrees which is irrelevant anyways) to a much simpler algorithm I found being used in the DiseqcU plugin for ProgDVB which uses very simple trig, the diamater of the earth, and the height of the satellites to calculate the rotation angle. The further away from south (or north) you calculate the angle for, the more you have to re-correct back towards south (or north). I haven't put a lot of thought into it, but a first guess at the problem I think could have to do with the angle present at the motor shaft. If anyone else has also noticed this and put some thought into what might be wrong, I'd sure like to get this figured out. As an example, for the furthest east satellite I can see just above the horizon, DiseqcU and the algorithm used in vdr-rotor and myth gives an angle of 75.46 degrees, whereas a real USALS receiver configured with the same reference location and same satellite location gives a motor angle of 70.4 (which considering how much further west I have to go from 75.46 to actually get that satellite is probably correct). Andrew Hakman
