[BC] Ground system

[Richard Fry]

>A Franklin is defined as 1/2 + 1/2 wavelength center fed.

However the currents on the upper and lower sections of a classic Franklin 
are in phase, but the currents on each side of a center-fed dipole are 180° 
out of phase.

A conventional center-fed dipole needs no r-f ground -- but a Franklin does, 
because essentially it is two end-fed monopoles in a collinear array.

>I'd always heard that to get free-space performance out of a dipole, it had 
>to be several wavelengths above earth ground.  Which would be kinda hard to 
>do at lambda = 300 meters.

A horizontally polarized dipole needs to be well elevated from the earth for 
its radiation pattern to resemble the free space form.

A vertically polarized dipole near the earth has a radiation pattern very 
similar to a 1/4-wave, series-fed monopole (link below).  The issue with 
using one is getting power to the feedpoint without radiation from the 
transmission line.

http://i62.photobucket.com/albums/h85/rfry-100/ElPat_V_Dipole.jpg

RF