Richard Clark wrote:
"The legendary characteristic of Sea Water is found in its far field
reflective characteristic which is remarkable due largely to its huge
SWR to fields---."

Yes, a wave striking the sea finds a high reflection coefficient and
ground waves do well too.

I am looking at a broadcast allocation book prepared by Cleveland
Institute of Radio Electronics in 1959. Many changes in stations and
coverage since then, but the book contains an estimated ground
conductivity map for the U.S.A. which probably has changed very little
since then.

Coastal Texas is almost as good as it gets when it comes to soil on the
map, 30 millimhos per meter. Seawater is not shown on the map but its
conductivity is given as 5,000 millimhos per meter or 167 times as good
as the best soil. Around New York City, conductivity is shown between
0.5 and 4 millimhos. Surface irregularities caused by structures make
additional attenuation.

The conductivities shown on the map are probably good averages as the
preparers had the propagation data of thousands of broadcast stations
which proved their performance to the FCC to work with.

Terman has a ground constant table on page 808 of his 1955 of his 1955
edition. Sea water is given a conductivity of 45,000 micromhos per cm,
or 45 millimhos per cm.

John Cunningham says in "The Complete Broadcast Antenna Handbook: on
page 309 that:
"The conductivity of the earth ranges from about 2 millimhos per meter
for dry sandy locations to as high as 5 mhos/m for sea water."

I think the figures given above are in reasonable agreement. I haven`t
researched the conductivity of carbon, but it is reasonably high being
used for motor brushes, battery electrodes, and vacuum tube plates.

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote (clip):
I am looking at a broadcast allocation book prepared
by Cleveland Institute of Radio Electronics in 1959.
Many changes in stations and coverage since then,
but the book contains an estimated ground conductivity
map for the U.S.A. which probably has changed very little
since then.
________________

The FCC's version of the US ground conductivity map is available on line at
http://www.fcc.gov/mb/audio/m3/

RF

On Thu, 2 Sep 2004 15:10:33 -0500, (Richard
Harrison) wrote:
Coastal Texas is almost as good as it gets when it comes to soil on the
map, 30 millimhos per meter. Seawater is not shown on the map but its
conductivity is given as 5,000 millimhos per meter or 167 times as good
as the best soil.

Hi Richard,

If all would review the standard FCC groundwave propagation curves,
they would notice that they offer low AM Band signal strengths in
terms of "conductivity" and that the differences in strength for the
5,000 millimhos per meter and that of 40 millimhos per meter (125 fold
difference) DO NOT achieve the same proportional difference in
received signal strength. In fact, the difference is so narrow you
could shave with a razor as sharp as it. Even at the high end of the
band the difference has to be out 700 miles to show the "conductive"
ratio. Of course, over that range of transmission ONLY Sea Water
would support that forecast as continental soil varies vastly in
smaller spans - hence the reputation of the Sea.

John Cunningham says in "The Complete Broadcast Antenna Handbook: on
page 309 that:
"The conductivity of the earth ranges from about 2 millimhos per meter
for dry sandy locations to as high as 5 mhos/m for sea water."

This is the conundrum of conductivity of earth: that there is so much
contradiction. You cite coastal Texas, but in distinct contradiction
to the dry sandy locations forecasts, pan handle Texas also exhibits
just as high conductivities for less water as Corpus Christi which
oddly enough easily has twice the sand content as those arid
wastelands.

There are a lot of reductionist statements about ground that simply
don't exhibit against the claims made for it. Reggie has long claimed
to be an authority on the subject, and when push comes to shove for my
hints that he offer Kelvinian substance, he complains about the CIA or
his insufficient understanding of English. The urchins of Rio would
guffaw at that one. I will anticipate Punchinello's Magic 8-Ball
answer "try again later," as I am sure the software could do no
better. ;-)

And by the way, the kitchen calibration of mud is a common gardener's
exercise, why Punchinello cannot or does not recite it is evidence
that no one really cares to ask (me or him). His embarrassment would
be found in its lack of correlation to RF (there are far more
variables to consider).

73's
Richard Clark, KB7QHC

"Richard Clark" wrote
If all would review the standard FCC groundwave propagation curves,
they would notice that they offer low AM Band signal strengths in
terms of "conductivity" and that the differences in strength for the
5,000 millimhos per meter and that of 40 millimhos per meter (125 fold
difference) DO NOT achieve the same proportional difference in
received signal strength. In fact, the difference is so narrow you
could shave with a razor as sharp as it. Even at the high end of the
band the difference has to be out 700 miles to show the "conductive"
ratio. Of course, over that range of transmission ONLY Sea Water
would support that forecast as continental soil varies vastly in
smaller spans - hence the reputation of the Sea.
_______________

For a reality check, here are the approx distances to the 1 mV/m contour for
1kW of radiated power from a 90 degree vertical with a good radial ground
system. The values were determined from the FCC's standard curves.

Freq Conductivity/Miles

540 kHz 8/66, 40/124, 5,000/140
1,600 kHz 8/22, 40/56, 5,000/126

The average ground conductivity in the U.S. is fairly low, probably
somewhere between 8 and 16 mS/m. The difference in ground wave propagation
over such paths is dramatically poorer than over sea water.

It is also clear from the above values how much better the low freq MW
broadcast channels perform.

RF

On Thu, 2 Sep 2004 17:17:00 -0500, "Richard Fry"
wrote:
It is also clear from the above values how much better the low freq MW
broadcast channels perform.

Hi OM,

You have a remarkable capacity to find controversy where there is
none.

Again, what is the contention that is your point?

73's
Richard Clark, KB7QHC

"Richard Clark" wrote
"Richard Fry" wrote:
It is also clear from the above values how much better the
low freq MW broadcast channels perform.

Hi OM,

You have a remarkable capacity to find controversy where there is
none.

Again, what is the contention that is your point?

73's
Richard Clark, KB7QHC
_______________

You quote only a part of my post with which you happen to agree, and then
say I find controversy when there is none.

The point of my last post on this subject, and our real controversy here
relates to which characteristic of sea water is responsible for its lower
groundwave path loss, as developed in the thread. You wrote that the reason
is because sea water is a good reflector. I wrote that it is because of its
good conductivity. This difference in our positions should be evident by
reading the thread.

RF

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"Richard Fry" and "Richard Clark" argue about:
...which characteristic of sea water is responsible
for its lower groundwave path loss...
...because sea water is a good reflector.
...because of its good conductivity.

Is sea water a good reflector because it has good conductivity ?

;-)




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On Sat, 4 Sep 2004 09:39:56 -0300, "Just a suggestion..."
wrote:

Is sea water a good reflector because it has good conductivity ?

If you think it has good conductivity, do you wire your house with it?
Do you have a radial field using #38 wire in a one meter grid? Both
laughable propositions here, but those tears of mirth turn to the
dewey eyed mist of religious belief when Salt Water "conductivity" is
mentioned.

Sand is the least lossy ground beneath your feet, but how well does it
contribute to DX? Add some water and the loss skyrockets - and this
is called the boon of conductivity!

No, it is called the boon of reflectivity. The Z changed and power
CANNOT penetrate the interface. If you cannot get power into it,
there is nothing to conduct (and it is the molecular polarization and
relaxation moment that causes this, not conductivity).

The legends of mature spinsters are many with respect to the qualities
of ground - they even inspire useless software as crutches. I have
seen NO ONE here who can recommend it (much less admit they don't even
have a clue on what values would be appropriate for their own locale).
Hence most discussion is either faith-driven, speculation, or simple
hucksterism.

73's
Richard Clark, KB7QHC

On Sat, 4 Sep 2004 06:42:45 -0500, "Richard Fry"
wrote:
You quote only a part of my post

Hi OM,

I don't quote the full message because it is already available, and
further, it is bad manners to do so unless something new and relevant
has been offered. None so appears.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote
Richard Fry wrote:
You quote only a part of my post

it is bad manners to do so unless something new
and relevant has been offered. None so appears.
_________

I doubt that the majority of readers will agree with you about the relevancy
of my posts on this thread to yours. You have simply chosen not to address
them.

But in any case...Pax vobiscum.

RF