Hi Ford,
> After doing a bunch of searching my literature and the web, nothing.
> It seems to me to be a perfect approach to inserting a phase delay to
> phase antennas in a favored direction. So little information appears
> available. Anybody got experience with these animals?
Goniometers do NOT, by themselves, vary phase delay. They vary
amplitude ratio (mostly between adjacent inputs) and can flip-the-
phase 180 degrees on any given input group (when rotated 180
degrees mechanically).
They are mostly useful for nulling receive signals in a bidirectional
pattern with broad lobes and a sharp null, like in DF'ing.
> For those that don't have the reference, the basic design is to insert
> three coils, one inside the other. Two are 90 degrees apart and fixed
> in position. The third is rotatable to obtain a delay (apparently).
That would be a two-pole. Mutual coupling varies as the
"secondary" winding is rotated past the poles. The goniometer
itself does not shift phase, other than a 180 flip. It only provides
amplitude variation between adjacent inputs as it is rotated.
If we fed the input poles at 0 and 90 degrees, we could obtain a
phase-shift of 0-90 degrees and 180 to 270 degrees but there would
be considerable amplitude shift. We need more phases (and poles)
to have complete phase rotation.
Continuously varying phase-delay, even just between two ports,
while maintaining a reasonable SWR is a major undertaking. We
also should remember in a phased-array suitable for transmitting
(reasonable efficiency) impedance of each element varies greatly
with phase-shift changes (being equal only at 0 and 180 degrees).
If we built something that worked we'd wind up with a VERY
complex system, and have very little or no benefit with a simple
system providing a few fixed directions. It certainly would not be a
simple goniometer system! There are much better ways to solve
the problem, but all are complex.
73, Tom W8JI
w8ji@contesting.com
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