RE: [TowerTalk] Gain Is a Function of Boom Length - True and Not True

[Jim Lux <jimlux@earthlink.net>]

At 05:10 PM 9/10/2003 -0400, Bryan Rambo wrote:
> I believe N0AX's statement to be true.  Thanks Ward!
>
> A corollary:
> No amount of clever engineering in areas of element interaction, feed
> efficiency, tuning networks (i.e. - traps), impedance matching gadgetry,
> etc. can make up for a short boom.
>
> True?

Not precisely...
There are some fundamental limits on a combination of gain and bandwidth 
(the classic reference is "Chu and Harrington").  You can theoretically 
make a small, high directivity, but very narrow band  and very inefficient 
antenna.  However, you can't get around the radiation resistance problem, 
which makes losses a problem.  Compact loops typify the problem.

And, using practical materials and practical construction, losses are an issue.

Also, to a certain extent, smaller means less effective aperture (think 
capture area), until you get to around 1/2 wavelength, where the antenna 
can be physically smaller, but still has an effective aperture of about 1/2 
lambda.

> 73 - Bryan W4WMT
>
> ----

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