John - KD5YI wrote:

Actually, on elevated antennas (as in the usual VHF setup), just two
quarter-wave radials 180 degrees apart is almost indistinguishable from 4 or
more radials.

Well, in theory yes, but in the real world , usually no. The reason
being the decoupling. Four or more radials will decouple the line
quite a bit better than two. I did tests adding radials to a VHF
ground plane, and I saw improvement with each addition of radials
I tried. Eight radials was a noticable improvement over four.
But I always put it down to the improved decoupling of the feedline,
rather than any big decrease in ground losses.
I imagine if you used separate decoupling sections to avoid feeder
radiation, the number of radials would matter little if any.
As far as elevated ground planes vs ground mount...Cecil does
have a point. It's common knowledge that a real low ground plane
generally sucks. You need many, many, more radials to equal
the ground loss of one at 1/2 wave up. While I don't doubt that
the low ground plane was beaten by the ground mount in Tom's test,
very few people actually run ground planes that low. If they do, they
can count on me to berate them for it.. IE: I often jumped on Cecil
for using one at appx 1/8 wave, and wondering why it didn't work too
well.
Thats too low, unless you have a lot of radials. In my observations
comparing ground planes, you really need to be at least 1/4 wave in
the air if you are going to use only four radials. Even then, thats not
optimum. At 1/4 wave up, 8-12 radials is closer to optimum. Four
radials at 1/4 wave is appx equal to about 60 on the ground.
By "optimum", I mean equals 120 radials on the ground...
Myself, I had a full length monopole on 40 m, with 32 ground radials.
It was rarely much better than my dipole on medium long paths of say
1500 miles. When I elevated the antenna to 1/4 wave, and used only
four radials, the performance was much better. Like day and night
really. So I agree, if you run an elevated GP, it needs to be up in the

air, or else you will need many radials. At 1/8 wave up, you need appx
60 radials to equal the 4 radials of the same antenna at 1/2 wave up.
I've heard many a tale of people running low band ground planes, real
low
to the ground, and having bad results. But you won't hear those bad
stories from the ones that run them at 1/4, 1/2 WL up.
MK