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*Subject*: Re: [amsat-bb] Determining max dopler shift for LEO's*From*: "John P. Toscano" <tosca005@xxxxxxxxxx>*Date*: Fri, 08 Jun 2001 09:13:44 -0500

Rodney Clayton (KA3BHY) wrote: > Is there a list or some way to determine the max > dopler shift I should see for rs-12 rs-15 fo-20 etc? Some tracking programs do that for you automatically. But in any case, if your tracking program will do a pass prediction that includes the range (distance between your QTH and the satellite), you can compute it yourself. (The easiest way would be to import the pass prediction into a spreadsheet, then you could even plot out the Doppler shift and/or actual ground station frequencies over the time course of the pass. Say you have two lines of the pass prediction listing. The critical fields you need are TIME and RANGE. Let's say they look like the following (totally fictitious numbers, just want to demonstrate the simple math involved): TIME RANGE 12:01:03 4,123 Km 12:02:18 4,423 Km Elapsed time = 75 seconds Range change = 4,423 - 4,123 = 300 Km = 300,000 meters Range Rate = (Range Change / Elapsed Time) = 300,000 / 75 = 4,000 meters per second Doppler effect = range rate / speed of light in meters per second = 4,000 / 299,792,458 = 0.00001334256 = 0.001334256% Doppler Shift = uplink or downlink frequency x Doppler effect If the frequency of interest was 145 MHz, the Doppler Shift would be 145,000,000 Hz x 0.00001334256 = 1,934.6712 Hz = 1.934 KHz. Hope that helps. John (KB0ZEV) ---- Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA. To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

**References**:**Determining max dopler shift for LEO's***From:*Rodney Clayton

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