Topband: Elevated Radials on Grounded Tower?

[Jim Brown]

I'm putting together a presentation which I think I'm going to call 
"Working 160M with limited antennas," or something like that. I've 
studied as much of the literature as I can find, including extensive 
work by W2FMI,  K3LC, N6LF, W8JI, and K2AV. My intent is to distill it 
to the point that it isn't overwhelming and come up with some relatively 
simple guidelines that guys can use to get on the air and have fun.

It seems to me that this work has been done in two forms -- careful 
modeling, and careful measurements, but not all of it has been done on 
160M.  In some one-on-one discussions, Tom, N6BT has emphasized that 
"the earth is fundamentally different on 160M as compared to 40M" where 
much of N6LF's careful measurements have been done, so that Rudy's work 
on elevated radials cannot be linearly scaled to result in guidelines 
for 160M.  I found radials at 4-6 ft ineffective on a new 160M antenna I 
had rigged, and Tom suggested 16-18 ft as a minimum height.  This summer 
I raised them to that height, and preliminary tests suggest that they're 
working fairly well.

One question I've not really seen a definitive answer to is the 
effectiveness of elevated radials on a GROUNDED TOWER. I'm most 
interested in any serious MEASUREMENTS -- the differences between a 
great radial system and a mediocre is usually only a few dB, far less 
than propagation and QSB, and, of course, quite dependent on ground 
conductivity.

I will, of course, be showing Guy's folded counterpoise as a small lot 
alternative, as well as noting W8JI's quite useful analysis of it.

I'm interested in the answer on a personal basis as well -- the new 160 
antennas are wires sloping from a 110 ft tower, insulated from the 
tower, fed at the base, one to the east, one to the west, fed one at a 
time.  The tower is a passive reflector, so loss in the radial system 
matters.  The tower is in a 4 ft cube of concrete, copper in the pour 
bonded to the tower and to six 8 ft rods. I currently have 10 on-ground 
#14 THHN radials on it, each 101 ft long (tuned to resonance with my 
MFJ259B).

Please respond on the list -- I suspect others will be interested, and I 
would appreciate the peer review.

73, Jim K9YC