[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: Re: [psk31] PSK31 Satellite Uplink on 10m (finalplan?)



> I wonder, now that we have now discovered that the 1 or so Hz per second
> of Doppler shift on the proposed 10m PSK satellite in LEO orbit...

OOPS... My use of the term "1 Hz" or so is a little bit of a stretch.  I
did it again thanks to the urging of IW3QBN.  Here is the 'change' in
Doppler per second over the typical passes of a LOW LEO.  Notice that
2/3rds of all pases are below 20 degrees and 96% of all passes are below
50 deg...

50deg 40deg 30deg 20deg 10deg  Peak Elevation of Pass
----- ----- ----- ----- -----
 4%    8%    16%   33%   67%   Percentage of total passes above this angle
----- ----- ----- ----- -----
 0.1   0.2   0.3   0.7   1.2   Doppler change in Hz per second
 0.3   0.5   0.7   1.1   1.9
 1.0   1.3   1.5   2.4   2.5
 3.5   3.8   4.0   4.1   3.0
 9.0   7.3   6.5   5.0   3.0
 6.0   5.5   5.0   3.5   2.5
 1.9   3.6   2.1   3.0   2.3
 0.5   0.9   0.9   2.0   1.5
 0.1   0.2   0.3   0.9   0.9

So 2/3rds of the time the Doppler rate of change is in the range of about
3 Hz per second or less.  It looks like  90% of the time it is 5 Hz or
less.  And worst case is 9 Hz change per second.

I did this recalculation for a worst case Spase Station Orbit.  I think my
nominal 1 Hz per second I must have remembered from an idea of several
years ago which was based on a much higher LEO, probably one of the RS
birds that is almost 3 times higher and has lower rates...

So, Peter, can PSK-31 be made to track these rates if it knows that it
should be watching the derivative of the rate?

Bob, Wb4APR


----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home