"Walter Maxwell" wrote in message
...
On Wed, 7 Sep 2005 14:07:39 +0000 (UTC), "Reg Edwards"
wrote:

MK,

How satisfying it is to read your message, written in plain, easy
to
understand, well-punctuated English, without any undeciferable
coded
abbreviations.

I agree with what you say although I am unfamiliar with exactly how
the FCC fits into the scheme of things.

Amateurs and commercial broadcasters have a common fundamental
requirement. There is a service area to be covered with a given
field
strength. Depending on frequency, requirements then diverge. But
the
design methods used to satisfy requirements are all confined (or
should be) to the principles of engineering economics. Inevitably,
the
Dollar, Pound, Frank, Mark, Rouble and the Yen rule the roost.

Both commercial broadcasters and amateurs do a cost-befit analysis.
The broadcaster takes into account the revenue acruing from selling
the service. The amateur, whether he likes it or not, has to ask
himself what the satisfaction of using the station is worth.

Amateurs' bank accounts are not unlimited.

Field strength at the limits of the service area depends on the
power
efficiency of the radiating system. If engineering economics
dictate
use of a set of buried ground radials then the peformance of the
ground radials must be included. Considering the system as a
whole,
it may be economical NOT to achieve the maximum possible radiating
efficiency. Indeed, the maximum is seldom the target.

If there is an economical choice in the matter, once the location
of
the station is decided, everybody agrees that efficiency depends on
soil resistivity at the site. To estimate efficiency it is
necessary,
at the very least, to make a guess at soil resistivity. Perhaps
just
by looking at the type of weeds growing in it. Or it can be
measured.

Depending on how far it enters into station economics, it is
possible
to numerically estimate efficiency from the number and length of
radials AND FROM SOIL RESISTIVITY.

B.L & E and the FCC don't enter into it.
----
Reg.

Sorry to disagree, Reg, but it appears you're overlooking an
important
point--the difference between the efficiency of the radiating system
itself, versus the efficiency of the ground area external to the
radiating system.

BL&E shows that when 90 - 120 (actually 113) radials of 0,4 w/l form
the ground system for a 1/4 wl radiator, the efficiency is 98.7%
efficient, REGARDLESS OF THE SOIL RESISTIVITY UNDER THE RADIALS.
This
is shown by obtaining the field strength of 192 mv/meter at 1 mile
for
1000 watts delivered to the antenna under the conditions described
above, compared to 194.5 mv/meter with a perfect ground having an
efficiency of 100%

It is only the soil resistivity of the ground external to the radial
system that determines the field stength external to the radial
system. Consequently, the soil resistivity (or conductivity, if you
like) is significant only in the areas external to the radial
system.

Walt, W2DU

=======================================

Walt, just what is it you cannot agree with? You appear to be making
an argument where none exists.

It is obvious there must be a distant point beyond which a large
number of radials will approach 100% efficiency regardless of ground
resistivity. B.L & E and the FCC arbitraliry decided on
1/2-wavelength and 120. Both nice round figures.

I'm sorrry to say you appear unable to agree that for the remaining
99.9% of all possible cases, ie., for cases less than 1/2-wavelength
and fewer than 120 radials, that GROUND RESISTIVITY in the immediate
vicinity of the antenna DOES HAVE A SIGNIFICANT EFFECT ON EFFICIENCY
and it cannot be disregarded.

My only criticism of B.L & E is that they forgot to measure soil
resistivity before leaving the site. And apparently, nobody has ever
bothered to go back and do it for them.

The only mention of their work occurs on this newsgroup. When laying
radials, 99% of amateurs forget B.L & E (if they have ever heard of
them) and the magic number of 120.

Hasan Schiers has recently given a blow-by-blow account of a sensible
way to lay a set of radials with the reasoning behind it.
----
Reg.