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Re: [TowerTalk] SP7GXP antennas?

To: towertalk@contesting.com
Subject: Re: [TowerTalk] SP7GXP antennas?
From: "Lux, Jim" <jim@luxfamily.com>
Date: Thu, 21 Oct 2021 17:43:47 -0700
List-post: <mailto:towertalk@contesting.com>
On 10/21/21 2:20 PM, john@kk9a.com wrote:
I would like to put up an isotropic antenna and compare it to my Yagis.

Yes, you could power your measurement system with a perpetual motion machine as well.


The Hairy Ball Theorem says that building an isotropic antenna is impossible. (https://en.wikipedia.org/wiki/Hairy_ball_theorem )

Hence, you build a standard gain antenna, the gain of which is calculate-able from dimensions and materials.

A dipole is easy, and fairly straightforward to calculate the gain (including ohmic losses).  As is a "short dipole".

Or, you build 3 antennas and do a three cornered hat.

The antenna range literature is full of practical solutions.


Free space gain measurements of large antennas is difficult.  I have seen some herculean efforts toward that end (promulgated by people who should know better).




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