I have a 4 Square relay box avail 75-80 m. which was produced by Colatchco,
Inc., the predecessor to K8UR COMTEK design. The relay box worked fine last
time I used it. I worked many rare DX , including China, both long and short
path on 75m. SSB, from MA. It comes with Colatchco user info, and some extra
plugin relays & warranty. Nice low angle take off and F/B is exc, using 43 ¼
wave verticals and ground radials (30 min per vert, 120 maximum performance)
This item is not part of DAVIS RF inventory, as we never sold these, because
Colatchco sold direct.Colatchco sold the rights to COMTEK.
The current COMTEK unit from DXE is advertised at close to $ 400.00 . I can
sell this for $ 195.00 + ship., w/manual, doc's and extra relays.
There is not a cover for the unit. It should not be hard to obtain one, or
fabricate it yourself. Or you can simply mount it inside an upside down pale.
DXE may be ab;e to buy cover from DXE. I can provide dimensions.
I will warranty the unit to work properly, as long as you test it within 15
days of receipt. More details will send you, complete install instructs.
Also,text and diag.for easy building of aluminum tube Verticals 73,Steve K1PEK
________________________________
------------------------------
Message: 2
Date: Fri, 23 Jun 2023 20:04:50 -0700
From: Jim Brown <jim@audiosystemsgroup.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] References for using a grounded tower as a
vertical radiator
Message-ID:
<0cf49764-23e2-afdf-56ae-785b13de3ca0@audiosystemsgroup.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
On 6/23/2023 11:51 AM, john@kk9a.com wrote:
> Other nearby towers or vertical metal structures can severely distort the
> radiation pattern.
Yes. Also "somewhat vertical" wires like the feedlines to wire antennas
like horizontal dipoles. These things can be modeled if we know
dimensions, including spatial details. I spent much of a summer about
ten years ago working out the interactions between a 120 ft tower with
antennas on top with my 100 ft Tee vertical for 160M; and between the
Tee and a pair of sloping wire verticals hanging from the tower that I
feed one at a time against radials.
The tower acts as a reflector for the Tee, yielding a few dB gain to
VK/ZL (also a corresponding null to Seattle), and as a reflector for the
sloping wires yielding a few dB in the direction of the slope; the Tee
acts as a reflector, kicking both patterns north by about 30 degrees,
yielding a few dB into JA or EU, depending on which I'm feeding. To make
all this work, I had apply a short at the base of the antennas that
acted as reflectors, which I did with a combination of feedline length
ad stubs.
73, Jim K9YC
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End of TowerTalk Digest, Vol 246, Issue 21
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