[Elecraft] Semi OT: vertical wire antennas

[Vic K2VCO]

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/