DDF1 • 5
c = Speed of light
We can calculate how fast the antenna must rotate in order to produce a
given Doppler frequency shift with the following equation
fr = dF x 1879.8/R x f
c
where
fr = The frequency of the received signal in megahertz
dF= The Doppler shift in Hertz
R = Radius of antenna rotation in inches
f
c
= Carrier frequency of the received signal in megahertz
As an example, let's calculate how fast the antenna must rotate in order to
produce a Doppler shift of 500 Hz at 146 MHz, assuming the antenna is turn-
ing in a circle with radius 13.39 inches.
RF Signal (fo)
A
B
C
D
Rotation
f o
+ f
- f
(B)
(A)
Figure 1
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