On 07/07/2019 16:50, David Tiller wrote:
-70 Hz at 50.313 MHz is a relative velocity of about -209 m/s or -468
mph. That's in the ballpark for a jet aircraft.
Hi David and all,
here is a handy web resource:
http://www.rfcafe.com/references/electrical/doppler.htm
note the first of the two formulae at the bottom of the page which is
most relevant. Particularly the extra factor of two to account for the
incident and reflected Doppler shifts.
With respect to the apparent prevalence of fixed frequency shifts, this
can probably be accounted for by more distant reflectors whose velocity
relative to the receiving and transmitting stations is changing at a
lower rate than for aircraft closer in whose paths have greater angular
rates or may pass overhead at one of the stations, thus reversing the
relative velocity.
The presence of Es reflected/refracted signals may include Doppler
shifted signals from aircraft reflections themselves, so during an Es
opening these frequency shifted/shifting signals may well be far more
common.
73
Bill
G4WJS.
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