[Elecraft] Franklin antennas

[Paul Christensen]

>"Both stations have extensive ground systems that would not be needed if
they were dipoles."

AMBC ground systems would still be needed (unless sited over salt water) to
maximize ground-wave coverage even if they were center-fed vertical dipoles.
The field intensity produced by a ground-mounted, center-fed 1/2 wave dipole
is the same as a voltage-fed (at the tower base) vertical radiator.  

The majority of omnidirectional, high-power AM stations use anywhere between
180 to 195 degree towers, voltage-fed at the base.  In essence, they behave
like vertical dipoles and in each case, they employ extensive radial
systems.  With either feed, maximum RF current occurs at the mid-point, and
maximum voltage at either end.  

I don't recall if the Franklin was developed before or after studies showed
that multi-lobe skywave radiation is minimized with 190 degree monopole
radiators.  That's the reason why so many legendary high-power stations use
a tower height slightly longer than a half-wave while ground field intensity
is essentially identical to the half-wave radiator.  

Paul, W9AC
(Ex-RKO Radio, Chicago)