[Elecraft] Windom Antennas
George, W5YR
[email protected]
Fri Jun 6 18:41:01 2003
Guy, you must have had some adverse experiences with verticals somewhere
along the line . . .
I use the Butternut HF-9V, ground mounted over a field of 18 radials each 25
ft long. The antenna resonates per the CIA-HF impedance instrument in each
of the 9 bands. It loads well with very low line SWR. Based upon the SWR,
impedance measurements and the design of the radial field, the total ground
loss is likely no greater than 3 dB and is possibly less. This is in a
typical backyard with trees, power pole and lines nearby, etc.
The key thing about the vertical is that in competition with a pair of
20-meter extended double zepps, mounted at 38 ft and at 90 deg, and a low
80-meter horizontal full-wave loop, the vertical many times produces better
signals than any of the other wire antennas.
I participate in the QRP-L Fox Hunts and most QRP operating events and fully
a third of the time, the most difficult contacts are made with the
vertical.
I find that it is noisier than the wires but not exceptionally so. Late at
night when 20 meters is largely asleep, it is interesting to monitor 14,100
and listen to the beacon stations and try the various antennas. You would be
surprised at how often the vertical returns the best signal, even from
locations favored by the patterns of the EDZs.
All your points are technically valid, and taken in summation would persuade
anyone that using a vertical is heresy. Nonetheless, with proper
installation and attention to the points you mentioned, a vertical - even a
"compromise" multi-band vertical - can provide superior performance when
conditions favor.
You might enjoy reading of the research done in the 70's with shortened
verticals by Jerry Sevick, W2FMI. His work was published in QST at the time
and is reprinted in appendices in "Building and Using Baluns and Ununs."
Jerry provides quite detailed loss measurements and the like for various
radial configurations, etc. I might add that Dr. Sevick, formerly a
scientist at Bell Labs, knows what he is doing, and his work can be relied
upon for accuracy.
Neither his work nor my experience and measurements can support your dire
predictions of 6-10 dB loss with a vertical for the reasons you enumerate.
73/72, George
Amateur Radio W5YR - the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"
<mailto:[email protected]>
----- Original Message -----
From: "Guy Olinger, K2AV" <[email protected]>
To: "Bob Lewis AA4PB" <[email protected]>; "Elecraft"
<[email protected]>
Sent: Friday, June 06, 2003 5:00 PM
Subject: Re: [Elecraft] Windom Antennas
> I agree with your statement about poor installation. Unfortunately it's
quite WORSE than that. Lack of a proper ground connection is only loss
factor #1. Note that poor series ground conductivity at a ground located
feedpoint does not apply to a series of "vertical" antennas that have feed
points up the antenna. But the rest below DO.
>
> Loss factor #2:
>
> An antenna will initially radiate about half its power below the horizon.
Horizontally polarized energy will essentially bounce at some angle, at full
strength.
>
> Vertically polarized energy will usually be absorbed instead of bouncing.
UNLESS the ground media at the bounce is salt water or laced with
conductors, like extensive dense buried radials. Both of those are rare in
the typical installation, since the vertical was chosen because of LACK of
good supports for horizontal antennas, or limited space, which means limited
space to place radials, if even practically possible.
>
> Loss factor #3:
>
> A vertical antenna has a lot of flux directly underneath. It penetrates
the ground to a surprising degree. If there is not a conductive dense screen
underneath (even for the "center fed models" not using the ground as a
current sink) the flux penetration of the ground will induce loss currents
in the area immediately underneath. This loss is completely independent of
any "ground connection" on the vertical.
>
> Loss factor #4:
>
> High current losses due to compromise tuning for multibanding, shortening
for convenience in construction can occur at aluminum joints, traps, and in
miscellaneous connections in the antenna.
>
> Loss factor #5:
>
> Trees, buildings, etc in the vicinity will all attenuated a vertical
signal to a higher degree than horizontal signals. This is especially true
at the low angles we are targeting in the first place.
>
> It's important to remember in this thread that the original post had to do
with a very limited installation of a compromise multiband vertical antenna,
not a W8JI ultimate vertical paradise.
>
> IF the owner has the time and inclination to do some work with radials and
specifically go after the loss factors, then some considerable success can
be had.
>
> UNFORTUNATELY, only a tiny percentage of the residential vertical
installations I have seen had 1 through 5 above attended to. Most were
significantly afflicted with these factors, initially not knowing what was
happening to them, and even a LOW horizontal antenna improved their results
dramatically.
>
> If one is going to do the "vertical" thing, DO the ***ENTIRE*** vertical
thing, or don't bother. Don't just stand the thing up, run coax to it, and
think you are done. This is particularly true for the QRP crowd, where the
6-10 db disadvantage you can accumulate in factors 1-5 isn't there to give
away in the first place.
>
> 73, Guy
> K2AV
>
> >
> > From: "Bob Lewis (AA4PB)" <[email protected]>
> > Date: 2003/06/06 Fri PM 04:40:35 EDT
> > To: "Elecraft" <[email protected]>
> > Subject: Re: [Elecraft] Windom Antennas
> >
> > > ...the joke about verticals is "radiate equally poorly in all
> > directions".
> >
> > I think verticals get this "bad rap" because the typical ham doesn't
> > install them correctly. No good radial or counterpoise system - shove
> > an 8-foot rod in the ground and call it "grounded". I wonder how well
> > a dipole would perform if you only put up half of it.
> >
> > The bottom line - it's usually easier to put up a "good" horizontal
> > antenna than it is to install a "good" vertical.
> >
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>
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