Hi Glenn,
You should be very worried about voltage breakdown of your base
insulator! Do you know how much RF voltage your base insulator
can safely handle?
A fourth idea you might consider is to simply use your tower to support
a 1/4 wave vertical wire for 80 meters, fed against the same radials you
use on 160 meters. This may be your easiest and most effective solution.
I'm sure other Topbanders use the same solution for 80 meters.
While a 1/2 wave vertical theoretically has a small amount of gain
compared to a 1/4 wavelength vertical, in actual practice useful gain
cannot be achieved when its mounted very close to average soil. The
situation would be different in a salt marsh.
73
Frank
W3LPL
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Glenn
Biggerstaff
Sent: Saturday, February 28, 2015 8:16 PM
To: topband@contesting.com
Subject: Topband: 160 Tower on 80
Hi all, I have a 90 foot Rohn 25 tower with an insulated base and insulated
guy wire sections for top loading ,base fed for 160 meters. It work great
,but I would like to use it on 80 meters as well.
The 3 ideas I have considered are voltage feed at the base with a resonant
LC network at the base, but I am a little worried about the voltages
present at legal limit power. Second idea,disconnect the top loading and put
a trap between the top loading and the tower to divorce the top loading on
eighty then an L network at the base for 80. Third idea, run a wire as a
sloper either a quarter wave fed against ground or a 1/2 wave dipole from
the tower.
Any thoughts or alternative ideas would be greatly appreciated.
Glenn WW4B
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