[BC] Directional Antenna Proofs - Ground systems.

[Richard Fry]

>My experience with VHF and UHF commercial and amateur 'ground plane' 
>antennas using flat or drooping wire radials, is that the horizontal plane 
>radiation flows along the radials, leaving voids inbetween radials. (etc)

H-plane radiation radiation from two elevated radials running in opposite 
directions cancels in the far field, because equal r-f currents flow on them 
in opposite directions at every point in time.  This effect is also shown by 
NEC software (NEC2 and NEC4).

Dr George H Brown of RCA Labs, Princeton NJ is the inventor of the ground 
plane antenna described above.  In his autobiography he wrote, "In our 
initial experiments, we found that only two horizontal rods worked just as 
well as four.  Many people from the Broadcast Sales organization came by to 
view our tests, and they always expressed doubts as to the ability to 
radiate uniformly when only two rods were used.  To quiet them, we used four 
for a while, thus stilling the criticism.  When the antennas became really 
popular, we did not dare confess our ruse."

It would be interesting to learn why the tests mentioned in Mr Potter's post 
appeared to show such h-plane directional effects with only two rods in 
opposing directions in the horizontal plane.

RF