[TowerTalk] Reverse feed System...(feed point?)

[Gene Smar]

Roger:

     My comments embedded below.


73 de
Gene Smar  AD3F



-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Roger
(K8RI) on TT
Sent: Saturday, April 23, 2016 6:37 PM
To: towertalk at contesting.com
Subject: [TowerTalk] Reverse feed System...(feed point?)

So how do you pick the feed point and radial heigh*t?
AD3F:  The article gives some detail about how to estimate the amount of
extra height various Yagi designs provide via their capacitive loading
magnitudes.  The article is a bit empirical in its approach to the height
estimates.

*
As for the spider beam, doesn't the coax to it make it look like top
loading?
AD3F:  I'm not sure what you're asking.  I'm not familiar with a spider
beam's mechanical design.



For Lightning safety the coax to the beam should be grounded at both the top
and bottom of the tower.
**
AD3F:  The shield at the top of the coax that feeds the multiple radials IS
grounded on the tower, just not at the TOP of the tower.  Given the examples
in N4KG's article, this shield/tower grounded connection could be from ten
to 50 feet or more above ground, depending on the magnitude of the top
loading available.  The bottom of this coax run could be, and should be,
grounded to the tower again before going to the shack.



73

Roger (K8RI)


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