On 8/16/2011 9:35 PM, Jeff Liebermann wrote:
On Tue, 16 Aug 2011 17:13:15 -0700, Jim
wrote:

I think the photo was on interferometry for direction finding, where
they were trying to plot the wavefront pattern. I recall the photo,
but I couldn't find it in the ARRL Antenna Handbook (19th edition).
However, the handbook does have a full chapter on direction finding
(Ch 14) which includes the cardioid antenna.


Could be..



The purpose of me using multiple bearings is simply to eliminate the
effects of reflections. It's not totally foolproof, but better than
chasing a single bearing.

There are better ways, but they're usually not very portable. A
rotating antenna direction finder can easily distinguish between the
incident signal from a reflection. Such direction finders display
something like the antenna pattern on a polar display. The incident
signal is very steady and does not move in azimuth. Reflections
jitter dramatically in both amplitude and azimuth. They also tend to
appear and disappear rapidly and erratically.

snip

Another method that I've used is to generate a narrow "beam" using two
identical yagi antennas that share a common reflector. snip



A popular scheme from WJ 30 years ago (at the advent of digital signal
processing) used 3 antennas in a triangle, and basically did
interferometry. Sampling the data and using an FFT lets you do a wide
band at one time (which is handy if you want to DF frequency hopping
radios, which became very popular in the 80s)