Re: Semi OT: vertical wire antennas
Posted by
Vic K2VCO on
Dec 20, 2010; 2:28am
URL: http://elecraft.85.s1.nabble.com/Semi-OT-vertical-wire-antennas-tp5851823p5851905.html
1. A wire should be as good as tubing.
2. Use at least 16 radials 30' long. You won't get much if any improvement by making them
longer and zig-zaging. Probably 32 would be a little better, but it's not worth it to use
more.
3. Do NOT put it against the trunk! The farther away from the tree the better. Trees do
absorb vertically-polarized RF to some extent.
4. You would most likely get improved efficiency from a remote tuner at the base of the
antenna than from a tuner in the shack. On some bands the SWR will be quite high on the
run from the tuner to the antenna.
On 12/19/2010 4:21 PM, Lew Phelps K6LMP wrote:
> I'm currently running my K3-10 into a 40 meter horizontal loop antenna, mounted on my
> roof about 35 feet above ground. It's impractical to use on 80, and has a very high
> angle of radiation on 40 and 20 meters.
>
> So, I'm thinking of replacing it with a 43' wire vertical. Yes, I know it needs a
> wide-range tuner, because it's non-resonant on any ham bands. I already have that. And
> I know that it needs a 4:1 balun. I can make that.
>
> I have three questions for the group.
>
> 1. Is there any reason to expect that a wire vertical will perform significantly
> differently than one made from aluminum tube (e.g. 2" OD at base)? EZNEC modeling
> shows a slightly lower gain for a wire antenna, but not significant. Is this borne out
> in real life?
>
> 2. The available grassy yard space where the antenna would be installed would permit a
> maximum straight-line radial run of approximately 30 feet, well under the desired
> length of 58 feet for operation on 80 meters. Would it affect antenna performance if
> the radials were laid out in a series of Z jogs rather than in straight lines?
>
> 3. The antenna would be suspended from a large sycamore tree. Will it make any
> difference in performance if I run the vertical right up the side of the trunk, as
> contrasted with suspending it from a limb at some distance (e.g. 5 - 10 feet) from the
> trunk?
>
> Thanks,
>
> Lew K6LMP
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/______________________________________________________________
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