My feeling is that this is much ado about very little... First, a 4 degree
difference in MODELED takeoff angle on 160 is meaningless...The presence of
power lines, house wiring, plumbing pipes, sewer lines, telephone wires, CATV
cable, and on, and on, within the near field makes the model nothing more than
a rough guide - very rough... Everything metal out to 3 waves is going to
have a major effect on your pattern...
Next the modeled TOA is only the peak point in the modeled wavefront... There
is vertical spread to the TOA and I suspect that the TOA -3dB points cover a
20 degree vertical angle, at minimum, so that would be roughly a 10 degrees to
30 degrees useable TOA ; a 4 degree change in the wavefront means nothing...
The percentage of time the arrival wavefront on 160 favors a TOA below 10
degrees is very small...
Third, the fable that an end fed half wave wire doesn't depend upon the local
ground is just THAT, a fable... If you work the antenna against ground it
doesn't matter a furry rodents fat pucker hole what the length of the antenna
is - you are working the antenna against ground and the local ground is the
major loss factor in gathering up the return currents, and the mid field ground
of 1 to 10 wavelengths out has lesser importance only because the biggest bite
on the signal has already been taken (not that the mid field is unimportant,
it's just that we have zero control over it)...
Now, if you feed the half wave vertical antenna as a doublet, then the local
ground is shielded from having to supply return currents, to some extent but
not completely, by the antenna balance, but ground at 1- 10 wavelengths out is
still going to play a major role... TANSTAAFL
And, Mininec way over estimates the low angle gain of vertical antennas over
ground... Take those gorgeous low angle patterns it shows with a large dose of
My instinct here is that you will be far better served by sticking to quarter
wave elements with smaller and cheaper balloons, and putting up a phased
pair... Use Al Christman's phasing lengths for the coax... a tuner at the
transmitter will allow you to move around the band with minimal losses... And
switching from broadside to endfire will allow directional gain, which will
help you hear the stations answering you......
cheers ... denny - never at a loss for an opinion
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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