I am building phased 80m verticals centered around a tower, my model
showed less interaction than if it was built near it but not centered.
K9RS had a system that may be of interest to you:
http://gofrc.org/pdf/multi-element_lowband_vertical_6.pdf.
I just returned yesterday from the Virgin Islands. The station was about
300 feet high with a sloping terrain to the sea. On 40m a low dipole
seemed noticeably better than a vertical with a poor radial system. I am
unaware of any software that can model a vertical on a sloping terrain.
John KK9A - WP2AA
To: TOWERTALK@contesting.com
Subject: [TowerTalk] 4 square for 80
From: Bill via TowerTalk <towertalk@contesting.com>
Reply-to: cqtestk4xs@aol.com
Date: Tue, 8 Mar 2016 20:37:58 -0500
I've always had real high towers and no restrictions on the amount of
towers I
could have. Out in KH6 it is different....one 90 footer on one plot of land.
Since that is a hard and fast rule, the quad loop systems for 80 meters I've
had on the mainland won't be nearly as effective...according to HFTA. I
really
can't get enough height for them to be real barnburners.
So....I've decided to try a four sqaure. Soil here is clay and stays wet
most
of the time, plus I have enough room to lay out a good radial system. The
grouind undulates a bit and slopes about ten feet or so in the direction
of the
Pacific which is about one mile away. The antenna site sits at 1100 feet so
the slope once it gets off the antenna site is great...about 1 foot drop for
every 5 feet of horizontal.
I've decided to go the Comtek route for the control.
Several questions:
First, any thoughts as how the terrain where the antennas are located will
affect operation? Also, any thoughts on how the big slope from the antenna
location to the ocean will affect the signal. On HFTA it is a big help on 80
with dipoles etc. but I'm not sure how it will affect a vertical system.
Second, I have two ways to go on the construction of the verticals. I can
fabricate aluminum full size quarter wave verticals which of course will
provide decent bandwidth, not as good as four towers, but better than wire
verticals. One problem is the location. The closest element would be
about 30
feet away from the tower whcih has seven Yagis stacked on it. The other
three
verticals are about 70-90 feet away(all to one side of the tower). Guy wires
are not the issue (Phillystran), but the tower is. I have no way to model
this
thing so it's pure guesswork how much the tower and other antennas (40-6
meters) will affect the signal.
Last, I could run four ropes from the tower at 84 feet and make wire
verticals
in a four square pattern around the tower. To increase bandwidth I am
planning
on running the vertical wires in a "cage". from what I've read that is
the way
to increase bandwidth. The problem with this of course is the proximaty
to the
tower. All four wires would be within 33 feet of the tower and the seven
HF/VHF antennas. So, the vertical system would "see" the seven antennas and
the 90 foot tower. Again it is guess work on my part as to what effect they
would have on the four square. No guy wires to consider since I am using
Philly. The other issue is I am afraid the 80 meter verticals would screw up
20 meters on my triband stack.
My gut feeling is the aluminum 1/4 wave verticals located slightly away from
the tower would be less affected by the tower/antnennas. However, for
ease of
construction I really would like to do the vertical wires around the tower.
This is my first foray into four squares so I would really like some
opinions
from guys who have experience in these matters.
Mahaho for the help!
Bill K4XS/KH7XS
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