[TowerTalk] HARD CORE NVIS for ADULT Radio Opeators

[David Jordan]

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