[Antennas] pseudo-doppler DF antenna(s)

[Johnathan Corgan]

On Tue, 2002-07-23 at 01:06, refmon wrote:

> Question 1:  In the experimenting sense, within reason, if one increases the
> diameter of the array, will this increase the Doppler effect?  Is there a
> rule-of-thumb relationship between subassembly frequency range and array
> diameter?  Back-figuring the catalog data does not reveal a general trend,
> but I do note that in all cases, high frequency segments are smaller in
> diameter than low frequency segments...I expect the Doppler effect is
> optimal only within some range of wavelength percentage that I have yet to
> realize.  Also, on the high frequency segment, which can be fairly small
> diameter, thus close to the central mast, is there a minimum mast-to-dipole
> clearance?

In theory, the pseudo-doppler effect is only useful out to 1/2
wavelength between antenna elements.  Beyond this there is ambiguity
error in the arrival angle.  In practice, it is less than 1/2 wavelength
due to velocity factor and mutual impedance in the antenna elements. 
Empirical testing by K0OV resulted in 1/3 wavelength spacing as optimum
for a 2 meter DF antenna.

Good reading is Transmitter Hunting: Radio Direction Finding Simplified
by Joseph Moell, K0OV.

-Johnathan, KG6KWT