[Antennas] Diminishing Returns

[Ron Youvan]

> I realize you can't have too many radials for a vertical antenna, but 
> where do you reach the point of diminishing returns.  Out of necessity 
> my Butternut HF6V vertical is set on a narrow strip of land and I can't 
> fan the radials out in a 360 degree pattern.  I can get about two sets 
> of radials for each band fanned out at about 180 degrees, but beyond 
> that the spacing between more radials will become rather close.  Would 
> more radials placed close together be beneficial or do I have about the 
> best I can expect?

> I have no previous experience with verticals.

   A club that I belong to had a 40 meter "antenna shoot out" using a 3" in diameter 
aluminum down spout pipe almost 30 feet long, 3 ten foot sections screwed together with 
sheet metal screws sitting on the top of a 2 liter pop bottle, on an aluminum plate with 
30 or 40 small screws on the 4 edges for radials.  We started with 4 radials 30' long and 
measured (far field) the field strength, we doubled the radials to 8 and we measured a 3 
dB improvement, I wanted doubled it again to 16, but I was voted down as most HAMS 
wouldn't run 16 radials.

   Every mobile antenna tested (connected to the same radial system) and the "isopole" 40 
meter antenna (up 10 feet) did no better than 10 dB below the reference antenna.

   The above antennas under test were the transmit antenna (through the same Bird Watt 
meter fed from the same transmitter, steady carrier) and the signal was received over a 
thousand feet away and relayed back on the 440 band by a linear translator and measured on 
a spectrum analyzer.  (everything was pre-tested)
So I can't answer your question, except to say: "the more the merrier."  They don't have 
to be any particular kind of wire, we used motor wire from a burnt up solenoid, except 
insulated wire will corrode much more slowly than bare wire.
-- 
    Ron  KA4INM - I'm proud to be Chuck's pop!