Hi, Bob
End feeding that 160m 1/4 wave as an 80m 1/2 wave should work great! For
several years I ran a vertical 40m 1/2 wave that I fed at the bottom through
a 1/4 wave of 450 ohm ladder line. Perfect match (almost 1:1) on the CW end
of 40m with NO TUNER! I could run it to full power with a FT-757 GX that I
had at the time with nop antenna tuner. It had good BW and runnng it all
across 40m was no problem, although I've always been mostly a CW DXer. I
workd everywhere on the planet with that antenna! I later added a reflector
and director for Bouvet and worked 'e first call in a BIG east coast pile
when they came up. (Jacky, F2CW at the key). Late It was a reall killer on
the evening 150 degree LP into SE Asia, and when ZS8MI came up, I almost
missed him because he was S9+20db on the FT-757!
No, you don't need any radial field under a vertical 1/2 wave. You'll be
driving a few thousand ohms, so a a few ohms or even 50-100 ohms of ground
resistance won't add any significant loss. A simple ground rod will do fine.
You can start and drive it with "slam-pipe" if you know what that is. (You
ight be able to borrow one from an electrical utility guy. And, as you say,
the high-current maximum will be up 1/4 wavelength so you'll have an
excellent low take-off angle! Enjoy!
BTW, when I did the 1/4 wave matching section, I did take care to feed the
antenna with the side of the 450 ohm line that was connected to the center
conductor of the coax, Of course, you could also feed it with an 80m
parallel-tuned circuit, that you would tap down to find the 50 ohm point.
Have fun!! I Think you'll be pleased!
73,
Charlie, K4OTV
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Bob K6ZZ
Sent: Monday, January 06, 2014 10:19 PM
To: topband@contesting.com
Subject: Topband: Feeding 160M Vertical on 80M
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
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