On Feb 3, 7:51 pm, "Ralph Mowery" wrote:
Has anyone modeled what happens to the signal of a triband 3 element antenna
that has one or more of the elements that has slipped on the boom say 10 or
20 deg ?

Also saw in an old magazine an antenna for 2 meters that had each element
offset by about 5 or 10 deg around the boom to produce circular
polarization. Will this actually work or is it wishful thinking ?


I've modeled similar things for sensitivity analysis of a design.
From a theoretical standpoint, what happens is that the mutual
coupling between the elements is reduced (to a first order, by
cosine(angle)), which changes the amplitudes and phases of currents in
the elements.

Net result.. not much change in forward gain (unless it's a very high
gain design with a lot of superdirectivity), pretty big changes in F/
B, if it was previously optimized for that. (that is, the nulls get
shallower.. a 1% change in currents can make a 20 dB null into a 17 dB
null)

As for making CP.. it might work, it might not. depends a lot on the
design. A Lindenblad makes CP with two elements about 60 degrees
apart. On CP in general.. it's easy to make elliptical pol.. tough to
make perfectly circular. This is particularly true if you want CP in
multiple directions (and it may not even be possible, depending on how
many directions.. viz the "hairy ball theorem").