On Mon,12/12/2016 1:55 PM, Catherine James wrote:
Jim Brown wrote:
Cathy James wrote:
It all depends what you are trying to do. For solid regional
coverage, a low dipole gives excellent NVIS coverage. For DX, it is
less than ideal.
That's an urban myth. See my tutorial on this.
http://k9yc.com/VertOrHorizontal-Slides.pdf A low dipole is much less
efficient than a high one. Especially study slides 18-22. Then fast
forward to slides 60-66.
A FAR better choice for something suspended between trees is a Tee
vertical, where a flat top wire provides top loading for the vertical
section, which does the radiation. Because antenna current splits
equally left and right into the top wires, radiation from the top
cancels, and you end up with a nice vertical radiator and a nice low
angle of radiation.
That's great for DX, but lousy for regional coverage. And here in
northern New England, our ground conductivity is awful, which makes
verticals challenging. No matter how much you improve the near field
with an excellent radial system, the far field will still have lousy
conductivity and that will push the radiation angle higher.
Lousy soil does NOT vary the vertical angle, it simply attenuates the
signal. In the near field, it burns transmitter power by warming the
worms. In the far field, it degrades ground wave and weakens the first
reflection that creates the vertical pattern.