Hi Mark -
A GOOD vertical antenna is perhaps the easiest way to get the low radiation
angle you would like for DX'ing. Some of the things you need to keep in
mid to get a "good" base fed system include -
1. The vertical should be long enough to have a relatively high radiation
resistance when compared to the groun/radial system
2. The length of the radiating portion of the vertical should not be more
than about 5/8's wave. You will start to get lobe splitting once you get
above a half wave and that will show up as, at first little, but growing as
the lenght increases, low angle "rabbit ears". At the same time the "main
lobe will be shrinking and risng and the desireable low angle radiation will
be decreasing.
3 You'll want an efficient tuner/matching network.
Another approach, if you are "radial system challenged" is to use a
centered fed vertical fed with something like 450 ohm feedline and a
"balanced" tuner. This generally requires a higher support structure, but
for the large part avoids the need for a radial system. I've found that 40-
45 feet (not critical) fed with 450 ohm line and a balanced tuner can be
quite effective for 10-20 and still quite useable on 40. General rule of
thumb: not more that 5/8's wave at the highest frequency, and/or at least .4
wavelength at the lowest frequency (half that figure for a ground fed
vertical).
Good luck with however you go.
Gene / W2LU
----- Original Message -----
From: "Mark Beckwith" <n5ot@n5ot.com>
To: <towertalk@contesting.com>
Sent: Monday, November 14, 2011 10:00 AM
Subject: [TowerTalk] verticlas used on multiple bands fed with a tuner
> Re: vertical antennas you can use on multiple bands with a tuner, are
> there magic lengths? I would just as soon put up one for "the low bands"
> and one for "the high bands." Or whatever. I figure the answer has
> already been determined long ago and I don't feel a particular need to
> discover it myself is someone can just tell me what the prevailing wisdom
> is.
>
> Thanks in advance,
>
> 73 - Mark, N5OT
>
>
>
>
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