Hi folks,
About a decade ago I installed a Jamaca NVIS... just 18ft over the old ancient
sea bed sand where I live... the four 40 m half wave wires fed in phase worked
good when the F2 layer was supporting refraction of 40m. This year I thought I
would attempt to improve the efficiency of the phased array with the
installation of four reflectors burried a few inches below the sandky loam.
The results appear significant although the estimate of improvement is
annacdotal at best. But stations I've worked with some regularity this past
year report a noticiable signal strength improvement. I suspect without any
scientific basis that those reflector wires have effected two aspects of the
system...one reduce earth absorbption (electrons wasted in radiant heating of
the nearby earth surface) and sharpen the highest take-off angle, perhaps
moving it to almost 90 degrees as well or just sharpening and providing some
gain in the process. I don't know.
My next experiment with this antenna is being considered. It would be
relatively easy to suspect four directors 18ft above the driven array. Any
thoughts on concept or EZNEC computations are much appreciated.
73,
Dave
wa3gin
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