On Thu, 19 Mar 2015 18:13:36 +0000, Johny B Good
wrote:


The rod in this case simply being a short electric field detector to
resolve which of the two possible directions that a loop antenna would
respond to on its own (normally using the null for most accurate
directional information). I think the loop would be used on its own to
get a bearing/reverse bearing and the 'stick' antenna would be
combined to determine from which of the two bearings the signal was
originating from.

In direction finding you start with the loop antenna only. You find
the signal, then turn the antenna until it disappears. The direction
of the antenna axis is now at 0 degrees to the target. The minimum
will be found again with the loop turned 180 degrees. You use a
minimum because it is far sharper in angle than the maximum. Then you
couple in the stick antenna and search this time for a maximum. This
will only happen in one direction, and it will identify which of the
two possibles is the right one.

An alternative form of direction finder uses two loop antennas mounted
at right angles. The signals from these are used to drive the x and y
axes of a scope. The phase and amplitude are such that the bearing of
the source is shown as a line across the screen. Calibrate it in
degrees and the job is done. You still need to resolve the 0/180
degree problem.

d