[TowerTalk] Isolating adjacent 4-Squares

Jim Brown jim at audiosystemsgroup.com
Mon Dec 21 14:17:41 EST 2020

On 12/20/2020 7:34 PM, Tim Duffy wrote:
> With elevated radials - everything is in play and you have bigtime coupling
> between the two antenna systems.
> Having high CMI chokes at the feedpoints of all elements is needed to keep
> the feedlines out of the picture.
> You will need to experiment - trying one thing at a time.

I want to reinforce the advice of others in this thread to extensively 
model EVERY part of your antenna farm, including unintentional 
components like towers, vertical feedlines to high dipoles, and even 
smaller conductive objects.

When I worked in a broadcast consulting office as an EE student in the 
early '60s, I learned that things like distant water towers could fill 
in the nulls of an AM broadcast directional antenna. The most sensitive 
part of most directional antenna patterns is not it's peak gain but 
their nulls. Peak gain in favored directions varies a dB or two from 
interactions, nulls can be affected by 10-15 dB.

73, Jim K9YC

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