This would closely resemble the antenna I have been using for many years.
What I use is an open-sleeve vertical consisting of three wires spaced about
4.5-inches. The center wire resonantes on 160 and is about 90' tall with a
top-hat. It hangs from a pine tree limb, and is fed against ground with a
simple coax feed (no matching network). The other two wires are for 80 and
75-meters, and are grounded, and spaced about 4.5 inches either side of the
ceneter "monopole". The grounded wires can be adjusted in length to give a
good match at 3.8 and 3.5MHz. Changing lengths of either the grounded wires
or the central monopole does not affect the resonant frquency of the other
wire(s), within reasonable limits.
This antenna can be scaled for 40/80 as well. Also, the central monopole
can be shortened on 160 (with a larger top hat) if you do not have 90' or
more to play with. This is a real good antenna with a perfect radiation
pattern on each band segment that it is designed for. No matching is needed
but I do use a 1:1 balun in a phase-inverter configuration at the feed point
to provide a direct DC ground for the central monopole element. I have
gradually perfected my design over the years to minimize twisting and
damage, which I would be happy to explain if anyone cares to engage in such
a conversation.
I have not modeled an Inverted-L in this configuration, but it might work
well with the 80-meter wires vertical (and grounded), and the 160-meter
element fed against ground and bent into horizontal somewhere above the
height of the 80-meter wires. It would be worth looking at.
Be aware that this antenna carries with it the same grounding/radial
requirements as any other vertical.
Wes, N5WA
-----Original Message-----
From: towertalk-admin@contesting.com
[mailto:towertalk-admin@contesting.com]On Behalf Of Jim Apple
Sent: Wednesday, October 23, 2002 2:32 PM
To: towertalk@contesting.com
Subject: [Towertalk] Parallel wire verticals
I've been considering building a BC Trapper (the
wire version of the Battle Creek Special) But I got
to wondering if I could skip the traps and run three
wires in parallel with a single feed instead ... The
40m element would be completely vertical the 80 and
160 elements would end up as inverted L's.
Any thoughts ? what kind of spacing would be best
?
Thanks in advance
- Jim
=====
- Jim Apple (WB1DOG)
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