On Jan 23, 2006, at 2:22 PM, John Geiger wrote:
> Low antennas are less than ideal, but will still work. I have a 40
> meter
> DXCC hanging on the way which was earned running 100 watts to
> pretty poor
> antennas-mainly a long wire at about 25 feet high or a dipole with
> a max
> height of 30 feet at the apex. Most small lots will still handle a
> vertical, even if you can't get alot of radials down. A vertical with
> nothing but a ground rod is better than QRT.
A dipole at a modest height will work well on 40m, but I had a lot of
trouble with 80m using a dipole at 30-40 feet.
I did some modeling with MMANA, and it's pretty obvious why - at that
height, just about all of the pattern is straight up. That may be
useful for NVIS contacts out to a couple of hundred miles. Depending
on where you live, that may be good for a domestic contest, but it is
no good for DX. For me in Georgia, most of the domestic ham
population is going to come in at angles below 50 degrees, and
certainly all of the DX.
I've had much more success the last couple of years by shunt feeding
my 15m tower for 80m and 160m. (The matching network has proved to be
an interesting challenge, as right now I am QRT on those bands
pending a repair) The models of even short verticals with a handful
of radials show nearly all of the pattern is below 45 degrees.
Seems like anyone in a small lot with trees or a modest tower can
have an effective vertical on the low bands. Plan for 20-30 radials,
as long as you can make them, up to about 1/4 wave.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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