Hi all,

I'm toying with the idea of an 'electronically rotatable' dipole setup.

Consider: a dipole oriented N/S
another dipole oriented E/W
They cross each other at the mid-point of each, forming a big plus
sign, like so:

|
|
----+----
|
|

If you feed the N/S dipole, you get an E/W radiation pattern.
Similarly, if you feed the E/W dipole, you get a N/S radiation patter.

If you feed the N/S and E/W dipoles simultaneously, you get a NW/SE
radiation pattern (for example), and if you flip the feed of either one
of them 180 degrees, then you get a NE/SW radiation pattern.

So far, so good. Now for the fun part. If you feed one of the dipoles
with a signal that is only 90 degrees out of phase (or 270 degrees), you
can get radiation patterns that take of in the NNW/SSE or WNW/ESE
directions, and if you feed the other dipole 90 or 270 degrees out of
phase, you get NNE/SSW and ENE/WSW directions.

What I am looking for is a circuit that can perform the necessary phase
delays, without having to use miles of coax coiled up in the shack.
Ideally, the circuit would be able to perform the phase shift on all (or
at least several) ham bands, so that it could feed into a pair of
fan-dipoles for operation on multiple bands.

Anyone have any suggestions on just how to accomplish this? In the
extreme case, you could have a continuously adjustable system, that
would permit you to point the 'virtual dipole' in any direction at all,
which might be useful when attempting to null out an interfering station
off to the side of the desired signal. However, in practice, I suspect
that the eight positions mentioned above would be sufficient to do the
same thing (albeit with the possibility of somewhat more signal loss due
to fixed aiming directions).

I seem to recall seeing a quote in the ARRL Handbook (or the ARRL
Antenna Book) from Roy Lewallen, indicating that there is no simple way
to do this. Am I mis-remembering (or mis-interpreting) what I read?

I know that the military does this sort of thing with radar systems, and
has for some time. However, their budget is quite a bit bigger than
mine, so perhaps their solution isn't 'simple':-)

Any thoughts on this, anyone?

Harry Gross