"Roy Lewallen" wrote in message
...

snip

A normal ground plane is a large sheet of metal that reflects the radio
wave
emitted by the radiating element.

"Normal"? Where have you seen an antenna mounted over a metal ground
plane many wavelengths in diameter? Perhaps a UHF antenna in the middle
of the top of a car, but that's about it.



snip

Which prompts me to ask a question: If a quarterwave vertical antenna has
many radials only a few feet above the ground, and these radials could be
made progressively longer and longer, does the antenna eventually fail to
"know" where the ground is? How long is "very long" to bring this about (if
it happens)?

I kicked some numbers around. By the formula two times
antenna_length-squared divided by wavelength [2D^2/lambda], I make the
far-field distance for a 14 MHz quarterwave vertical be only 2.5 meters
[less than a quarter wavelength] ... but typical radials are already longer
than that, aren't they? So this isn't a near-field/far-field boundary
issue, is it?