[TowerTalk] Modeling a ground plane

[Bill Turner]

I am modeling a full size ground plane with four elevated radials for
40 meters using EZNEC v. 3.0. I have it six feet above ground.

I noticed that changing the length of the radials has much less effect
on the resonant point than changing the vertical element. 

For example, on 40 meters, changing the vertical element by one foot
moves the resonant frequency by about 200 kHz, but changing all four
radials by one foot moves the resonant frequency much less, only about
20 kHz or so. 

I'm curious why this is. I would have thought the effect would be the
same. 

All comments appreciated. 

73, Bill W6WRT