I tried to use a halfwave vertical with a parasitic reflector on the beach
in Grand Cayman (ZF) two years ago. I fed my vertical in the center
as a vertical dipole. I modeled it with AO, but when I put it up the SWR
was terrible. I changed it to 1/4 wave verticals and they worked great
being only 1 meter from the ocean. I never did figure out why the vertical
dipole didn't work. When I took the vertical down and layed it on a
chair the SWR was good. I later suspected the coax running down side
of the vertical may have been the problem and I wish I tried pulling it out
horizontally from the antenna. I'd like to try it again sometime when I'm
on a Caribbean vacation.
73,
John
-----Original Message-----
From: David Douglass
To: towertalk@contesting.com
Sent: 8/29/2001 8:11 AM
Subject: [TowerTalk] halfwave verticals
Hi all,
I'm in the process of building some halfwave verticals to use portable
on HF
with the aid of a DK9SQ telescoping fibreglass pole.
I am building the LC matching system to convert the high impedance at
the
end of the halfwave down to the 50ohms to match the coax.
My question is this! I'm sure in the past I have seen a computer program
that allows you to key in the frequency and it will give you the length
required and the values of inductance and capacitance required.
Does anyone know were I can locate this program or if there is a manual
calculation I can use for the LC values.
Regards
David, VK2DPD
vk2dpd@qsl.net
vk2dpd@bigpond.com
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List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 96 feet for under $1500!! http://www.anwireless.com
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FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
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