On Apr 30, 3:56 pm, Owen Duffy wrote:


So it seems that one could do as you suggest and effectively isolate the
radiator and radials from ground, or the radials need to be carefully
adjusted to minimise the mast / feedline current to ground, especially
where the feedpoint resistance is small wrt the equivalent mast to eart
resistance.

Owen


Any elevated radials need to be resonant, and show a low Z at
the freq being used. If they show a high Z, they are basically
useless. You have to think of them more as the lower half
of the antenna, rather than ground radials. I read a post of
Roy's the other day that kind of touched on this. There really
is no "RF ground" when elevated, according to him, and I agree.
It's all one total antenna same as any other.
Of course, the number of radials used for the lower half of the
low GP antenna will greatly effect the ground loss, and to some
extent the decoupling of the feedline.
I've noticed that adding more than four radials to a 1/4 wave GP
on 2m did improve decoupling.
So even if ground losses are not an issue, IE: the 2m example,
the performance can still be improved by improving the decoupling
of the line. And it's noticable too.
But with your low band, low height antenna, ground losses are
a larger issue than decoupling. 2 radials are going to be lukewarm
at best, even elevated at your low height in wavelength.
Your ground losses are going to be pretty high.
MK