Richard Clark wrote:
"Salt water is miserable as a conductor, and its special place in the
pantheon of noble applications has little to do with conductivity."

I praise the god of conductivity for the ocean`s behavior as a beniign
enabler of medium wave propagation over extraordinary distances as
compared with ordinary earth. The reason the ocean`s surface allows long
distance propagation is explained in part on page 15 by Ed Laport in
"Radio Antenna Engineering":

"Nothing can be done about the electrical characteristics of the grouind
or topography between transmitting and receiving antennas. By choice, it
is possible to locate the antennas in areas of the best available soil
conductivity, thus to increase the terminal efficiency to some extent,
and to increase this efficiency still further by proper design of the
grounding system. (For ground waves vertical systems are imperative as
there is zero horizontally polarized ground wave propagation.)

Optimum ground-wave propagation is obtained over salt water because of
its conductivity (many times that of the best soils to be found on the
land) and uniform topography."

Laport has a ground-wave propagation table on page 17 of "Radio Antenna
Engineering". It is for low frequencies which best exploit ground-waves.

At 1000 miles over seawater, a wave at 400 KHz is attenuated by 98 dB.
Over good soil, 111 dB. Over poor soil, 160 dB.

Soil resistance determines penetration depth nto the soil and loss that
the soil extracts from a wave, especially if the frequency isn`t too
high. At 10 MHz and above, over real earth, the earth`s capacitance
offers so much less opposition than the earth`s resistance that the
earth`s resistive opposition really does have very little to do with
conductivity. However low the soil conductivity is, it is effectively
bypassed by the earth`s susceptance.

Sea water is so good at limiting medium-wave penetration and loss that
broadcast stations can be heard far out at sea during daylight hours.
This range is much greater than over any type of land. I recall hearing
the steel guitars of Hawaiian music when we were approaching from the
U.S.A. during WW-2. We were still days away and the sun could be high in
the sky. It wasn`t all that far as we only traveled about 250 miles a
day in good seas. Field strength increases by 6 dB every time you cut
the remaining distamnce by half as you approach the station. At half the
distance the volts per meter double.

Best regards, Richard Harrison, KB5WZI