"Richard Clark"
I've seen no discussion of actual quantifiable results against these
claims offered, so there is every chance that they are pinned together
by the evident circularity:

1. There has been no measurement of ground conductivity by BL&E
2. Reggies model for ground conductivity counters NEC-4
3. NEC-4's model for ground conductivity conforms to BL&E
4. There has been no measurement of ground conductivity by BL&E
_________________

At least now you admit that BL&E didn't measure ground conductivity. That's
progress.

First things first. The goal of BL&E's experimental work was to relate the
'efficiency' of MW vertical radiators of various electrical heights to
radial ground systems of various configurations. It did not state or find
that ground conductivity had any significant bearing on this, and, as shown
by their measured results, it did not.

The entire theoretical section of this paper where ground currents are
calculated, and the references to ground currents that were measured during
the experimental work could have been omitted both from consideration and
measurement without changing the conclusions of the paper. None of that was
significant to their measured results for field strength vs system
configuration, which was the purpose of their efforts. And omitting it
would have spared you your confusion.

The FCC considers every non-sectionalized AM broadcast vertical radiator of
a given electrical height using a given radial ground system to have a given
efficiency. Period. Ground conductivity at the radiator site has nothing
to do with that. It doesn't matter whether that site is in the middle of
Kansas with 30 mS/m conductivity, or on Long Island with 0.5 mS/m, radiation
emitted from a given antenna+radial ground system will be the same. The
purpose of the BL&E field work was to determine those efficiency values, and
it did so with high accuracy. Their findings have been a benchmark
confirmed at many hundreds (probably thousands) of AM broadcast station
applications since 1937.

By the way, even NEC-2 can be used to confirm the results of BL&E's study,
by inserting at the bottom of the vertical radiator a low-value DC
resistance simulating the resistance of the radial ground system connection
with a perfect ground plane. This again shows that ground conductivity is
insignificant in determining the radiation 'efficiency' of a MW broadcast
vertical and its radial ground system.

RF