[TowerTalk] SP7GXP antennas?

[Lux, Jim]

On 10/21/21 2:20 PM, john at 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).