Topband: Best angle of radiation ?

[Paul Christensen]

> AM broadcast band antennas 5/8 & 1/2 wave tall are rarely used any more. 
> I noticed a reduction of the tall AM towers starting  about the 1960's.

An optimized half-wave design (180-195 electrical degrees) is still the 
height of choice for AM broadcasters.  There are many factors, including 
financial, land acquisition, etc.-  that preclude the use of these optimized 
radiators, but given the choice, an optimized half-wave design is preferred.

Yesterday, I pointed out that these half-wave designs were preferred since 
they simultaneously maximize gain at zero elevation while minimizing skywave 
radiation.  It would have been more correct to state that the optimized 
half-wave design maximizes gain at zero elevation while simultaneously 
minimizing *high-angle lobes* that are associated with radiators over about 
195 degrees in height and that includes the 5/8 wave radiator (225 
electrical degrees).  It's the high-angle skywave component that's 
destructive to AMBC listening.

Paul, W9AC