hi

I was reading about a few different variants of the spider beam type
multiband HF antennas.

A few of the designers seemed to indicate to me that the antenna
works 'best' ground mounted at around 30-40 feet or so but not
greatly higher.

When I asked if it would work 'ok' on the roof of my building at
100+ feet was told no way over 40ft it would work poorly



It started me thinking, I couldn't really see why it wouldn't
work or work better at height, or at least as good

I do understand potential for change in radiation angle, but not why
the antenna gain would take a dive



the kinds i've seen seemed to be either moxon like kinda
simular so I would think that these designs would be fine at
height if not better (for certain things)


anyone think of something i might have overlooked in the spider like
designs that would actually 'kill it' at 100ft? (talkin about
gain/electrical performance NOT wind damage)


just couldn't see anything that would prevent it from working at
height




thanks

Nearly all horizontally polarized antennas of a few elements have a very
broad free space elevation pattern. So when mounted over ground, they
all tend to have nearly the same elevation pattern (except for
front-back directivity), dictated primarily by the height above ground.
In other words, a spider beam, quad, or two or three element Yagi has
about the same elevation pattern as a dipole at the same height. There
are some heights which are particularly good, and some which are
particularly bad, for working stations certain distances away because of
the elevation angles where the maxima and nulls occur. But those heights
are essentially the same for dipoles, quads, and Yagis as they are for
spider beams.

Roy Lewallen, W7EL

ml wrote:
hi

I was reading about a few different variants of the spider beam type
multiband HF antennas.

A few of the designers seemed to indicate to me that the antenna
works 'best' ground mounted at around 30-40 feet or so but not
greatly higher.

When I asked if it would work 'ok' on the roof of my building at
100+ feet was told no way over 40ft it would work poorly



It started me thinking, I couldn't really see why it wouldn't
work or work better at height, or at least as good

I do understand potential for change in radiation angle, but not why
the antenna gain would take a dive



the kinds i've seen seemed to be either moxon like kinda
simular so I would think that these designs would be fine at
height if not better (for certain things)


anyone think of something i might have overlooked in the spider like
designs that would actually 'kill it' at 100ft? (talkin about
gain/electrical performance NOT wind damage)


just couldn't see anything that would prevent it from working at
height




thanks