This is an example of a Ground Low Velocity Factor antenna.
A 1200' wire on the ground is quite lossy. That means that current
induced from the feedpoint toward the far end will be effectively
self-terminated, reduced to a large degree by the time the induced
current has traveled to the end and reflected back. For a wire that
long, the presence of a far end termination may not make any
discernible difference in front-to-back performance. Depending on the
lossiness of the ground, the effective gain (and the pattern) of the
antenna is most likely set by the first electrical wavelength from the
feedpoint. The rest of the antenna from the far end is too attenuated
by travelling next to the lossy ground to make a difference.
The velocity factor of wires on the ground can vary from 45 to 85
percent depending on the ground, varying with situational moisture
content, so the pickup pattern of signals from the desired direction
will vary. This is proven out by the wide variety of results of such
antennas. At least in the desert, the situational moisture content
does not vary and whatever performance will be steady.
73, Guy.
On Tue, Jan 5, 2010 at 2:10 PM, <kd6nrp@earthlink.net> wrote:
> Good Morning:
>
> Back in the mid-1980s I discovered that long (1000, 1200, 2000, and 5000
> foot), end-fed, insulated wires on the desert surface were superb receive
> antennas for VLF through at least 4 MHz.
>
> I once placed an Y-shaped array of 1200 foot wires on the ground and
> connected them to a switch box that allowed me to select one wire as a
> receive antenna and the others as counterpoise wires. It was awesome for AM
> broadcast band use (good gain and very directional).
>
> I wonder I deployed a doublet with two 1200 foot wires or a Y-array of 1200
> foot wires on the desert floor, and connected it to my transciever through an
> antenna tuner, if it would work well on 160-meters.
>
> And yes, I actually did deploy a 5000 foot wire. It worked well for receive.
>
> 73
>
> Brian, KD6NRP
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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