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...............
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