I just built a 4 wire cage inverted vee, hanging from my tower,
and feed it with about 85 feet of DXE400MAX cable. With the
VSWR low point at about 3625 kHz, the worst-case VSWR
is just under 2:1 at 4000 kHz. A bonus is, with a vacuum relay
in a plastic box, I can drive it against ground on 160m. My rig's
ATU easily tunes it on 160m.
vy 73,Bryan WA7PRC
http://www.tinyurl.com/wa7prc-80m-160m
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Date: Fri, 18 Aug 2017 07:34:43 -0700
From: Grant KZ1W
Subject: Re: [TowerTalk] Broadbanding 80 meter dipole
The ARRL Antenna Handbook has a number ways to broadband a dipole,
several probably difficult as noted.
One not in the current handbook is the Witt/Leeson tuned coaxial
resonator feed method, see
http://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1993/09/page27/index.html
At QRO on 80m, small coax such a Davis RG8X-LL will be ok and RG6 is QRO
capable for the 75 ohm section per W8JI evaluations. There are no L, C
or relays in the air, it's a plain wire dipole and the coax is needed
anyway to feed it, so it is cheap, light, and easy to maintain.
I've built one with RG8X-LL and Belden 8281 double shield video cable
(often cheap on ebay) for next year Field Day but not run the in the air
swr curves yet. As with any dipole there is height sensitivity so for
this application modeling with the tower is a good idea. I modeled it
for my application with EZNEC/4 and optimized it with AutoEZ and the swr
is < 1.6:1 from 3.5 to 3.92Mhz, rising to 2:1 at 4.0MHz.
Grant KZ1W
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