[Elecraft] Windom Antennas

Fri Jun 6 18:03:01 2003

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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