Topband: T-loaded vertical

[Ed Sawyer]

The answer to the top loading is that the top is essentially the same as if
it was an L on the antenna - just with the connection point moved to the
center.  I would add maybe 5 ft on either side of the top to that equation
and see what it looks like when you install.  And, like other verticals. If
it gives you a good SWR right off the bat, then your ground losses are too
high.  It ideally wants to be around 20 Ohms.  I can't get mine down past 30
Ohms because of the really poor ground in Vermont.  I started with 24 and
kept adding 6 radials (1/4 wave) at a time until I saw no difference with
the feed point impedance adding the next 6.  That had me end at 48 radials
per T on a 2 el phased array.

 

I was surprised by Frank's comments.  I would get 50 - 75 feet away - but
"hundreds of feet away" would seem too far to have a parasitic element have
effect on a yagi.  Especially a 10, 15, or 20M yagi.  I guess it would be
easily modelled to see.

 

Ed  N1UR