something that will enhance such an antenna is to raise a portion of
the wire off the ground 2 or 3 feet (use an arrow, staple to a wood
fence, or field expedient bush etc), leaving the last 25% or so laying
on the ground. the elevated portion will have substantially improved
radiation performance and will have a faster velocity, but the 25%
left on the ground will act as the beverage termination...
If you do this with the long leg of K3MT's Grasswire Windom (eg 70 ft
elevated, 26 ft on ground) you'll get gain in the direction of the
long leg, and a reasonable FB ration too... The back leg (short
side) can be cut down to about 30 ft with out too much impact on the
swr at 40m and above.
Another couple benefits are: the vertical lobes which a significant
to an elevated beverage are dramatically smoothed, and the antennas
may be array'ed at relatively close spacing. Two of the K3MT
Grasswire Windoms can be laid out in parallel about 25 ft apart, and
fed in phase ( simple power splitter and equal length coax is good
enough) as a two element broad band array. Such an array will
approach -3 dbi (~20 TOA) at 15m.
Some additional info can be found by googling " Eyring Low Profile
antenna "
Have fun
niel
WA7SSA
On Dec 7, 2008, at 10:23 AM, David Cutter wrote:
So, if you made it 19% longer with some zig-zags, it would be
resonant in the middle of the cw band and no need for matching, just
connect to coax. I imagine it's fairly broad band being so close to
the earth.
David
G3UNA
David Cutter wrote:
Sounds like this one:
<http://users.erols.com/k3mt/graswire/graswire.htm>
[referring to my original post]
A few minutes before the start of the ARRL 160m contest I decided
to try something I'd heard about. I took about 180 feet (55m) of
wire and laid it on the ground from my shack, across the
backyard, around the back of my garage and all the way down the
edge of the driveway.
My 180' wire was resonant at about 2.2 mHz, where the SWR was
around 1.4:1. Since signals not down all that much compared to the
vertical, I am sure that it would have worked as a transmitting
antenna, and possibly without a tuner if I had lengthened it a bit.
The interesting part is that it doesn't need to be straight to
work. This could be very useful in a real emergency.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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