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*Subject*: Re: [amsat-bb] Where Does Doppler Occur?*From*: Bob Bruninga <bruninga@xxxxxxxx>*Date*: Sat, 1 Dec 2001 13:55:34 -0500 (EST)*In-Reply-To*: <000901c17a86$1b407520$9c212904@vz.dsl.genuity.net>

> I have been wondering... Doppler shift... where precisely does it occur? Easiest way to visualize it is simply the "range" or distance from you to the satellite. The only thing that causes Doppler is a change in the range. WHen it is approaching, the range is changing rapidly shorter giving a + Doppler. When it is departing the range is changing rapidly longer (- DOppler). When it is at its closest point to you, the range is hardly changing at all (thus 0 Doppler). Thus if you plot range/rate over time, you get an "S" curve. The steepness at the center depends on how close the satellite's closest point is to your observation point. Stand in the middle of a railroad track, and the DOppler is exactly +X approaching you and -X going away, and it switches instantly (assuming you survive). But if you are a mile from the track, then the rate of change is much slower...but still starts and stops near the same values. You will get LOTS of answers to this one, I am sure.. Enjoy, Bob ---- Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA. To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

**References**:**Where Does Doppler Occur?***From:*James Alderman, KF5WT

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