Lloyd Berg N9LB wrote:
There were numerous technical write ups about stations who wanted the maximum theoretical ground wave signal and spent big bucks to put up 5/8 wave verticals. They were always disappointed in the unexpectedly reduced coverage area that resulted. Most of the reasoning for this unexpected negative result was attributed to the minor high-angle lobe produced by the 5/8 wave coming back down and interfering with the main lower angle signal. As a result, those station who had experimented with 5/8 wave towers usually reduced them to 1/2 wave or less.
Note that the above effects are not present for AM BCB stations operating with fairly low power (say 5 kW and less), and/or on higher BC frequencies and/or where earth conductivity is poor.
In those cases the groundwave has already fallen below the ambient r-f noise level within the radius where those high-angle skywaves start returning to the earth -- so no self-interference occurs.
R. Fry
_______________________________________________ Topband reflector - [email protected]
