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RE: Doppler



If your tracking program displays range rate then you can calculate it from
there, ... but given the temperature instability of most 2.4 GHz
downconverters, the calculated frequency would only be within +/-6kHz
anyway.... so you'd sill need to hunt, though not as much.

f* = f0 * ( 1 - (vr / c))

where f* is frequency observed on ground

f0 is frequency at source (2401323000Hz)
vr is range rate in m/s
c is speed of light 2.99792458e8 m/s

you'll have to scale the units as necessary for whatever your tracking
program displays in.

Calculate f* first then adjust for RX converter offset (-2256MHz for a down
to 2m converter), ...

so final calc becomes f* - 2256000000 for the dial frequency


Paul, VP9MU

-----Original Message-----
From: Jack O'Mara
To: AMSAT-bb
Sent: 2/18/01 12:53 PM
Subject: [amsat-bb] Doppler

Is there a simple way to determine doppler shift using the
normal outputs from a tracking program? I have some problem
finding the AO-40 signal on 2401 by not knowing the amount
of doppler shift. When sigs are weak its better to know
about where to start tuning. 

Any info would be appreciated.

73
Jack W4AD

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