[TowerTalk] 80 Meter beam
jim.thom at telus.net
Sat Apr 1 16:16:20 EDT 2017
Date: Fri, 31 Mar 2017 20:19:52 -0700
From: Grant Saviers <grants2 at pacbell.net>
To: john at kk9a.com, towertalk at contesting.com
Subject: Re: [TowerTalk] 80 Meter beam
I would add that there are some interesting wire antennas (what started
this thread) with low angle gain such as phased dipoles, V's and delta
loops that well done aren't mega investments.
## what else that has worked in the past is a short boom, like 15-25 ft long,
close to the top of a tower, with a sloping 80m dipole, center fed, at each end
of the boom, going off in opposite directions. IE: short boom is oriented
N-S...with one sloping dipole, sloping towards the N.... and the other sloping south.
Then a full size delta loop Reflector is placed at the center of the short boom, next to the
tower. Apex up, flat side down. What u end up with is a delta loop reflector that is common
to both sloping dipoles. Then u end up with some FB, and gain in each direction. Simple,
works, and directions easily switched.
## That wire array in the old ant book also works good, the one with 5 x sloping half wave dipoles,
spaced 72 deg apart around the tower, or tree etc. All fed with .375 wave long coax. The un-fed
4 x sloping dipoles become reflectors. The .375 coax on each of the un fed coaxs has both its center
and shield opened off via relays. Then XL is added to the dipoles, so they appear a bit longer.
3 db gain and 20 db FB is typ. The ones I saw did not use any CM choke at the feedpoint ,
only on the input side of the relay box.
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