On Oct 1, 4:00*pm, Jim Lux wrote:
Richard Clark wrote:
On Thu, 30 Sep 2010 14:44:53 -0700, Jim Lux
wrote:

It was written by BL&E that
120 radials work,

2, 15, 30, 60, and 113.

No discussion whatever of 120.

I stand corrected.. thanks..
So they extrapolated to 120 as a "nice round number" for the future
purposes of the FCC.

The only reason the FCC used 120, is overkill for the
stations to be able to avoid a costly survey.
If they didn't use 120, they had to do tests to prove
that the system was efficient enough. So most used
120 to avoid all that.
For most cases, 120 is almost twice overkill..
For ham use 60 is usually plenty to get well into
the near optimum range. Any more than that is
a small increase, and usually not worth the cost
of the wire.
Since Owen posted this question, I did a lot more
checking around, and I had already seen the MW BC
examples.
Seems I'm not the only one that doubts that a small
number of barely elevated radials will give a large
increase over ones on the ground.
One that is in my camp is... Yuri will love this..
W8JI.. Tom seems to agree with my stance from
what I can tell. He has done tests in this regard
and his results did not show much of an increase
over the ground installed radials.
In fact, he gave one example where they changed a
MW station from four elevated radials to the usual
buried radials.. I assume 120 of them..
They then had to explain to the FCC why the buried
radials suddenly gave 5 db+ gain over the supposedly
"near perfect" elevated set.. :/
He also did tests on 80m comparing this same thing.
The results did not pan out and pretty much were in
the same ballpark as the results I saw when I tried it.
IE: the elevated radials are slightly better than the same
number on the ground, but only by a small amount.
His tests showed that the usual buried radials using
60 or more greatly outperformed the three or four
elevated radials. By 5 db+..
Myself, I think for four elevated radials to equal even
sixteen on the ground would require them to be almost
1/8 wave off the ground.
So it seems I'm not alone in my doubt of this
supposed free lunch program. W8JI seems to be
in my doubtful camp. A few others too actually.