> The 5/8th was abandoned because the high angle lobe commonly
> landed in the fringe groundwave area, and it had a null at
> the most common useful skywave angle. This gave rise to
> severe fading right where they most wanted to extend the
> signal.
As a project for an Electromagnetic Fields and Waves course I was taking
back in the early 1960s I plotted the elevation patterns of unsegmented
verticals of various heights. The objective was to produce the maximum
ground wave while minimizing any sky wave radiation.
A vertical of 190 electrical degrees was best for this purpose, just a bit
longer than a half-wave (180 deg.), but well short of a 5/8-wave radiator
(225 deg.). This antenna has a low-angle lobe that is almost as potent as
the 5/8-wave without any wasted vertical radiation.
Of course, vertical stacking could be used to further enhance the main lobe,
but my professor felt that the cost of the resulting tall antennas would be
beyond the means of all but very large market stations. (I think he had a
consulting gig going on on the side and was having me do his grunt work!)
Gus Hansen
KB0YH
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