[TowerTalk] Re: [Dx] question about G5RV antennas
Mon, 9 Jul 2001 15:57:32 -0400
I think it might be useful to point out that multi-lobe gain is not "free
Any gain from splitting an antenna's pattern into many lobes with
many nulls results in an average gain, or useful gain, that is much
less than the gain predicted at lobe centers.
The more nulls and lobes the antenna has, the less useful the gain
is no matter how carefully you position an antenna that can not be
rotated when in use. What happens is the fellow you are trying to
work can just as often be in a null as in a peak of the pattern, no
matter what his location, when the lobe is too narrow.
Eznec for windows allows you to determine average gain, which is
more useful for antennas like dipoles used at harmonics.
Gain is not always a good thing, unless you can move the antenna,
because signals do not always come from the same directions
even when you are working the same areas of the world!!
For example...last night, CX1SI was coming from ESE even though
by great circle heading he is about due south of me.
> The pattern and gain will be different on every band.
> Where the antenna acts as a long wire, maximum gain
> will be in the lobes closest to the wire, typically 25 to 35
> degrees each side of the wire depending on length and frequency.
> Here is an empirical analysis I wrote on the subject in 1997.
> There might be 2 dB gain at the center of the peak lobe
> on the high bands. Less on the lower bands.
73, Tom W8JI
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