[amsat-bb] Re: probably simple

Larry Gerhardstein gerhardstein at montana.com
Thu Jan 7 23:42:56 PST 2010

Bob W7LRD,

I disagree that Doppler shift will be zero when your window to work 
northern EU is optimum.

In SatPC32, I just did a Tracking->Preview and determined that when the 
AO-07 footprint includes both the northwest USA and northern Europe, the 
down link Doppler is +2.8 and up link Doppler is -8.3.

Note, the numbers +2.8 and -8.3 were for orbit #60844.  I also 
determined that if a different orbit, then you get different Doppler 
shifts.  Determine the pass that you wish to attempt a contact and use 
the Doppler numbers you get from Tracking->Preview for that pass.

Next pick a frequency using VFO mode in SatPC32 and do some 
experimenting.  You may need to waste a window of opportunity, but using 
a ratio of -8.3/2.8 uplink to downlink Doppler, you should be able to do 
a respectable calculation.

Another problem: The Doppler for the station in northern-EU will likely 
be different than yours.  This means you might wish to coordinate with 
the station over there as you attempt contact. When I tried to enter 
grid JPnn into SatPC32, it would not accept it.  It calculated NAN (not 
a number) for latitude.  Don't know what that's about.

However if you're using CW & not SSB, this may make little difference.  
As long as you're getting a CW signal in the band pass of your RX, you 
should be able to copy.

And remember, the squeaky wheel gets the oil.  Keep making noise about 
this on this BB until something works.

I know you wanted a simpler answer.  Hope this does not seem too 
complicated.  The Trig/Math to work this out is possible, but tricky.

Good luck.

73, Larry W7IN (home=DN27 Plains, Montana)

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