Topband: Isolation of tower to antenna

[Dr. Wolf Ostwald]

hi !
for years i ran a shunt fed tower with a 6 el 20m yagi on top as a tx 
antenna for 160. I made sure that the antenna was well connected to the 
tower and nothing happened.
Instead of trying to find a material that is electrically suficient as 
well as mechanical, i would simply change the feeding. I can see no 
reason to decouple the top yagi structure from the tower. At the same 
time this has hazards in lightning protection too.
The extra capacity formed by the Yagi on top enhances the radiators 
efficiency even further ( if its not already at least a full quarter 
wave high )
All of this said without knowing all the detail of the installation.
I´d go for a Gamma match , equalize potentials on the top, and be done 
with it and have no worries about insulation etc.

73 de wolf    df2py