Topband: 160 Tower on 80

[donovanf at starpower.net]

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 at contesting.com] On Behalf Of Glenn 
Biggerstaff 
Sent: Saturday, February 28, 2015 8:16 PM 
To: topband at 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 
_________________ 
Topband Reflector Archives - http://www.contesting.com/_topband 

_________________ 
Topband Reflector Archives - http://www.contesting.com/_topband