[VHFcontesting] Re: Gain from an omnidirectional antenna

[Jim Worsham]

You are correct.  The horizontal loop gets its gain by not radiating very
much energy vertically.  It's pattern looks kind of like a doughnut.  A
horizontal loop will give you a few dB of gain but better than a yagi?  They
have got to be kidding.  Sounds like you should be teaching them about
antennas.

73
Jim W4KXY

----- Original Message -----
From: "John Geiger" <johngeig at yahoo.com>
To: <vhfcontesting at contesting.com>; <vhf at w6yx.stanford.edu>
Sent: Wednesday, April 16, 2003 8:46 PM
Subject: Gain from an omnidirectional antenna


> I have an antenna question for the reflector.  On the
> local repeater here, the general consensus is "Get a
> horizontal loop for VHF, they will outperform yagis".
> (I know better, but hey, I just report what I hear).
> So here is my question-I have heard gain figures
> attributed to loops, or to stacked loops, but I don't
> understand how.  If an antenna is truely
> omnidirectional, where does the gain come from?
>
> As I understand it, a beam gets its gain from focusing
> its RF in the forward direction.  It takes the
> radiation that would go to the front and sides, and
> compresses it into the forward direction instead-or
> something like that.  The gain comes because you lose
> radiation in other directions.  But if an antenna is
> onmidirectional, it is not compressing the signal into
> one direction more than the others.  So how does it
> get gain?  The only idea that I can come up with is
> that it must cut down on the vertical lobes, taking
> the energy from several of the vertical lobes and
> focusing it into one or two vertical lobes.  It can't
> do it in the horizontal plane, or then it wouldn't be
> omnidirectional.
>
> So am I even on the right track with this question or
> thinking?  As you can tell, the local club really
> needs a good course in antenna fundamentals!
>
> 73s John NE0P
>
>
>
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