Topband: Feeding 160M Vertical on 80M

[Michael Tope]

On 1/6/2014 7:18 PM, Bob K6ZZ wrote:
> Folks,
>
> I have a 60' tall top loaded vertical for 160M and would like to know how
> best to feed it to use it on 80M as well.  On 80M there will be some pretty
> high voltages at the feedpoint.
>
> Other than dealing with high voltages, is doing this a bad idea (or good
> idea) for any partcular reason(s)?  The high current point would be higher
> above ground which seems beneficial at the very least.
>
> What would be the best method for matching it on 80M?
>
> Do 1/2 wavelength ground mounted verticals require the same quality ground
> radial system that 1/4 wavelength verticals require?
>
> Thanks and HNY to all!
>
> 73, Bob K6ZZ

Bob,

I have a 56' top loaded vertical for 160 meters (it also has some 
inductive center loading) which was built from parts from a Gap Voyager. 
I wanted to use the antenna on 80 meters, but I didn't want to mess the 
possibility of matching a really high input impedance, so to keep things 
simple, I put a short yardarm at the top with a pulley (~ 2ft offset). I 
use the pulley to pull up a separate parallel vertical wire for 80 
meters. It includes a single short top-hat wire beyond the pulley 
insulator which I pull away at an angle to bring the parallel wire into 
resonance on 80 meters. I use an Ameritron RCS-4 four port remote switch 
at the base of the antenna to switch between the 160 meter feed which 
goes through a 1:4 Unun (12.5 to 50 ohms) and the 80 meter vertical wire 
which is direct feed. I have a pretty extensive radial system under the 
antenna (~50 radials 100 to 125ft long). The system seems to work 
reasonably well on both bands.

73, Mike W4EF/6...............