Date: Sun, 02 Mar 1997 16:25:37 -0800
From: Jan & Del Seay <email@example.com>
X-Mailer: Mozilla 3.0 (Win16; I)
To: Jim Reid <firstname.lastname@example.org>
Subject: Re: [TowerTalk] V-Beams (long-delete if no interest)
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Having plyed with long-wire array, I would like to make a couple of
comments, re your project.
a) The idea is sound - but remember that if you use resonant
wires for bi-directional use, (an antenna is said to be resonant
when standing waves are present) the frequency range is really
limited, A 180 degree phase reversal is forced at the far end,
as the direction of travel reverses. Therefore, a very narrow
range of frequencies are available where the voltages in each
direction are additive. Not likely you will get much gain over
2 or more amateur bands. By terminating the wires, you eliminate
the reverse voltage and gain is obtained over a large frequency
b) Using PVC, or similar material for spreaders is probably not a
good idea due to the weight of the material. The best spreaders I
have used are 1/8" thick X 6" long X 3/4" wide wood pieces that
have been boiled in parafin. Very light, and impervious to weather
and UV radiation.
c) The Amidon baluns are not extremely rugged. I bought three of
their 6:1 baluns for 300/50 ohm feed of folded dipole elements
and the longest any lasted at 1.5 kw was 2 months. A better
choice (but more pricey) is the Palomar Balun that is designed
for tuned feeders with very high vswr. At $80.00 it is twice
as high priced, but I haven't been able to destroy one.
Of course, using a link-coupled matching device (such as the
Johnson Matchbox design) is the best choice.
Remember to keep the high swr on the tuned feeders, not on the coax.
Good luck with the project. Vee Beams and Rhombics are the best
antenna' around. Still kick butt even with all the new technology!
73 de KL7HF
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