[amsat-bb] Re: sat-com (figured I better change the subject)

Greg D ko6th.greg at gmail.com
Thu Mar 27 20:53:26 PDT 2014

Howie DeFelice wrote:
> "I bet (a small bet anyway) my cell phone carrier doesn't save receive
> frequency data accurate enough to determine what direction I am driving
> though."
> You are probably right since the doppler shift is pretty small ( at least I hope it is :) ) on a
> cellphone. The satellite access is MA-TDMA so the burst timing and frequency offset need to be tracked.
> This is a useful performance metric when troubleshooting connectivity issues in a big network.
> - Howie AB2S
If my math is correct, doppler shift for a car driving 60mi/hr directly 
towards a non-moving cell tower (not always a safe assumption in 
California) would have a Doppler shift of about 90 hz, assuming a cell 
frequency of 1 ghz.  There's probably considerably more variation in 
your carrier frequency due to temperature, power supply factors, and 
component ageing, though I suppose with time these could probably be 
determined and backed out.

Greg  KO6TH

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