One thing that I've never seen mentioned anywhere is a multiple-band dipole fed
with ladder line. The reason I'm curious about it is that I used to have an
80-Meter Inverted Vee fed with ladder line, and the performance was great on
80M. For 160M contests, etc. I would add about 65 feet to each leg so that it
became a full-sized Inverted Vee for 160. However, in doing that, even though
the tuner matched it just fine on 80M, my great 80-Meter performance went away
until I removed the 160M extensions. I always wondered if I could have had
both, if I had built up a combination 160 and 80M Inverted vee with both sets
of elements off of the same ladder line feeder, like may people do with
coax-fed multiple dipoles. Anyone ever try something like this?
LJ
-----Original Message-----
From: Keith Dutson <kdutson@sbcglobal.net>
Sent: Jun 28, 2005 8:11 AM
To: TowerTalk <towertalk@contesting.com>
Subject: Re: [TowerTalk] Improving my dipole
I would hang the dipole with extra wire pointing down instead of in the
trees. IOW, move the suspension line on both ends toward the center. There
is little current at the ends. Keep the ladder line (light weight, low
loss) and run all the way to the shack entrance. Use a current balun there
(under eave usually best location) for coax changeover, or just keep the
same connection you have but form an RF choke using about 8 turns of coax on
a 1 foot diameter.
73, Keith NM5G
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Art Boyars
Sent: Monday, June 27, 2005 8:34 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Improving my dipole
On the CQ-Contest Reflector K7QQ said: "You have to keep in mind that the
best antenna doesn't exist. You can only get up what you can and it is never
enough." Well that's where I am, but I'd like advice from you experts on
how to improve my antenna, within my personal constraints.
My antenna is a dipole, about 99-ft long, strung between maple trees of the
neighbors on either side. (It's already much higher than the peak of my
roof. No other supports available.) The feed line is mostly window-pane
twin lead, with several feet of coax to get into the house and reach the
Transmatch. Yeah, I know it's not balanced; but should I really care, as
long as the RF goes somewhere other than losses? (And I know that the high
SWR might cause the coax to arc over or have noticeable resistive loss, but
that's one of the constraints -- for now.) My main operating interest is SS
CW, with a little other casual contesting (work the Club members and the big
guns) and a bit of 40M CW DXing (if I can get the antenna to work better).
I've pulled the ends of the dipole as far as I can into the trees (maybe too
far), but it still sags quite a bit -- 5 to 10 feet, by eye. Some of the
sag is probably from the weight of the antenna wire and the feedline, but I
think a lot of it is simply from the dipole's being longer than the span
between the trees.
I have two seat-of-the-pants concerns. First, I may be getting losses from
having the ends of the dipole in the foliage. Second, the vertical-V might
be more NVIS-like than Iis good for me. Obvious solution is to shorten the
dipole a bit, but that would make it even shorter than the recommended
100-ft minimum. So, first question for the experts: Do you think I'll do
better to shorten it, or should I leave the ends in the trees?
Second-order solution and question: If it turns out that the feed line is
weighing down the center, would I be better off to let it sag than to change
to something more like TV twin-lead? (I recall some discussion here about
Radio Shack selling a twin-lead with heavier-than-typical conductors.)
Thanks for your help.
73, Art K3KU
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
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