RE: [amsat-bb] Doppler correction?

["Robert McGwier" <rwmcgwier@xxxxxxxxxxx>]

I think Paul's suggestion is a good idea.  I recall how
Brooks Van Pelt did this with the table loaded version
of KCT control: he did a calculation of when and how
much using linear interpolation and a finite difference
estimate of the slopes of these "lines".  You set
your tolerances and giving a couple of points a time
to update is computed and on the nearest timer interrupt,
Brooks fixed the frequency and/or updated the antennas.
It was pretty neat and all in fairly neat assembly language:
ahhh, the good old days, when we walked twelve miles
to school, uphill both ways, in a foot of snow, thirteen
months a year. This would be a mouse flatulence in a hurricane
on today's computers.

Bob
N4HY


> At 10:06 PM -0500 11/10/03, Anthony Monteiro wrote:
> >InstantTune updates the frequency every second.
> >There is no simple way to change this since it
> >is driven by InstantTrack/OrbitDRV which updates
> >the satellite velocity every second.
> 
> Nominally every 1.7576 seconds (32 ticks of the PC's 18.2 Hz 
> clock).
> 
> It should not be difficult (for me) to provide a patch to OrbitDRV 
> that makes this happen more frequently, if that's useful. It might 
> be 
> better architecturally if the tuning program just interpolated, 
> though.
> 
> The original value was chosen to be slow enough that OrbitDRV's 
> calculations didn't use up too much of the CPU even on the slowest 
> 8088-class PC. On anything approaching a modern computer, that is no 
> 
> longer a problem. Now the limitation would be how fast InstantTune 
> can command the radio.
> 
> 73  -Paul
> kb5mu@amsat.org
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