Richard,

Are you sure you meant the statements quoted below?

Horizontal polarization bounces just fine from "horizontally conducting
surfaces". Indeed, when a mixed polarization wave hits a conducting
surface the horizontal polarization in the reflected wave is enhanced,
not "short-circuited". This is the same phenomenon that is the related
to Brewster's angle.

Perhaps you really meant to say that a special guided wave mode, namely
the ground wave, does not support horizontal polarization.

73,
Gene
W4SZ



Richard Clark wrote:

[Lots of more or less correct stuff snipped]


Well, this is where you are in over your head (water metaphors are
abundant in this topic). This, again, requires presumptions insofar
as the original observation was driven by the AM example. However, at
this point we will depart from the low frequency mandate to examine
another mandate: polarization and your presumption of conductivity.

A horizontally polarized antenna seeing a horizontally conducting
surface is a scenario that describes a self-short-circuit.
Horizontally polarized waves meeting the earth (a conductive one)
immediately snuff themselves (how long would your car battery last
with a screwdriver held across its poles?).

On the other hand, vertical antennas do not suffer this fate - and for
the same reason: it is a current wave (or at least the magnetic
component inducing such a current, in a conductive earth) that spans
earth making a perfectly reasonable relationship to continued
propagation.

[More snip]

On Wed, 05 May 2004 08:49:22 -0700, Jack Twilley
wrote:

comments
seen on Mr. Cebik's site (usually associated with graphs of antenna
patterns made with different types of ground) led me to believe that a
quasi-infinite plane of salt water goodness would be a huge boost.

Hi Jack,

Let's not lose track of why this is true, rather than fixating on the
downside of alternative illusory explanations. We have DXers here
frequently gushing about their shore installations.

We also had reports from one fellow who maintained a regular schedule
with an Aussie who worked CW mobile in his car coming home from work.
Our man here could literally see the variation in signal strength as
he approached or moved away from the shore down under.

Now, this report is typically known as anecdotal. However, when you
can repeat the observations and correlate them to your hypothesis (as
they did), then such reports gain materially.

73's
Richard Clark, KB7QHC

On Wed, 05 May 2004 22:38:06 GMT, Gene Fuller
wrote:

Richard,

Are you sure you meant the statements quoted below?

Horizontal polarization bounces just fine from "horizontally conducting
surfaces". Indeed, when a mixed polarization wave hits a conducting
surface the horizontal polarization in the reflected wave is enhanced,
not "short-circuited". This is the same phenomenon that is the related
to Brewster's angle.

Perhaps you really meant to say that a special guided wave mode, namely
the ground wave, does not support horizontal polarization.

73,
Gene
W4SZ

Richard Clark wrote:

[Lots of more or less correct stuff snipped]

A horizontally polarized antenna seeing a horizontally conducting
surface is a scenario that describes a self-short-circuit.
Horizontally polarized waves meeting the earth (a conductive one)
immediately snuff themselves (how long would your car battery last
with a screwdriver held across its poles?).


Hi Gene,

Vertical polarization is the only mode that the Brewster Angle works
for (that's why polarized sunglasses work so well, they are
contra-polarized for what DOES reflect).

To test your hypothesis, use EZNEC over a perfect ground and note the
distinct difference at low angles (less than 5 degrees). The
horizontal radiation lobe is an example of Lambertian (another Optics
term) distribution where the maximal gain is observed directly
overhead, and only when phases positively combine (due to the high
surface conduction presenting a second source). Other phases give
rise to this Lambertian distribution which is much like the lobe
characteristics of a headlight glowing in the fog.

73's
Richard Clark, KB7QHC

On Thu, 06 May 2004 00:01:19 GMT, Richard Clark
wrote:

To test your hypothesis, use EZNEC over a perfect ground and note the
distinct difference at low angles (less than 5 degrees).

I might add, compare this horizontal's low angle performance to its
free space performance (a world of difference from that nearby
"conductivity" and none of it remarkably "good" even for the most
perfect of grounds). You have to hoist your horizontal pretty high to
bring the phase gains into play.

73's
Richard Clark, KB7QHC

Richard,

Is that you, or did your evil twin steal your role on RRAA?

Try reading my comment again. If you still disagree, then perhaps you
should crack open any elementary physics or optics textbook.

I did not mention antennas or lobes. I was commenting on your assertion
that the horizontal polarization is "shorted out" at a conducting
surface. Utter nonsense.

73,
Gene
W4SZ



Richard Clark wrote:
On Wed, 05 May 2004 22:38:06 GMT, Gene Fuller
wrote:


Richard,

Are you sure you meant the statements quoted below?

Horizontal polarization bounces just fine from "horizontally conducting
surfaces". Indeed, when a mixed polarization wave hits a conducting
surface the horizontal polarization in the reflected wave is enhanced,
not "short-circuited". This is the same phenomenon that is the related
to Brewster's angle.

Perhaps you really meant to say that a special guided wave mode, namely
the ground wave, does not support horizontal polarization.

73,
Gene
W4SZ

Richard Clark wrote:

[Lots of more or less correct stuff snipped]


A horizontally polarized antenna seeing a horizontally conducting
surface is a scenario that describes a self-short-circuit.
Horizontally polarized waves meeting the earth (a conductive one)
immediately snuff themselves (how long would your car battery last
with a screwdriver held across its poles?).



Hi Gene,

Vertical polarization is the only mode that the Brewster Angle works
for (that's why polarized sunglasses work so well, they are
contra-polarized for what DOES reflect).

To test your hypothesis, use EZNEC over a perfect ground and note the
distinct difference at low angles (less than 5 degrees). The
horizontal radiation lobe is an example of Lambertian (another Optics
term) distribution where the maximal gain is observed directly
overhead, and only when phases positively combine (due to the high
surface conduction presenting a second source). Other phases give
rise to this Lambertian distribution which is much like the lobe
characteristics of a headlight glowing in the fog.

73's
Richard Clark, KB7QHC

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

Gene, W4SZ wrote:
"---I was commenting on your assertion that the horizontal polarization
is "shorted out" at a conductive surfacce."

Richard Clark`s description may be indelicate but as I recall, Terman
says rouighly the same in several instances. Wish I had a copy at hand.
Terman says that a horizontally polarized low-angle wave suffers a phase
reversal upon reflection and as the difference in path length is
negligible between incident and reflected waves at low angles, the waves
being of opposite phase add to zero.

Best regards, Richard Harrison, KB5WZI

On Wed, 5 May 2004 21:49:41 -0500, (Richard
Harrison) wrote:

Gene, W4SZ wrote:
"---I was commenting on your assertion that the horizontal polarization
is "shorted out" at a conductive surfacce."

Richard Clark`s description may be indelicate but as I recall, Terman
says rouighly the same in several instances. Wish I had a copy at hand.
Terman says that a horizontally polarized low-angle wave suffers a phase
reversal upon reflection and as the difference in path length is
negligible between incident and reflected waves at low angles, the waves
being of opposite phase add to zero.

Indelicate or blunt, the results are the same. The Lambertian
distribution of a characteristic that is painfully 30 dB down due to
the presence of a perfect conductor plainly evidences severe loss. It
can't be the ohmic loss of conduction as this would negate the premise
of a perfect conductor, it can't be the dissipation factor of an
insulator for the same reason.

The electric dipole moment is clearly bridged by a conductor, by
definition. As such, at the interface, it must collapse completely
into a current which gives rise to counter emf, the two waves cancel
as a function of phase - the proof again is found in the Lambertian
distribution that vanishes completely with the removal of ground (why
horizontal antennas are held up in the air). The more remote the
ground, the greater the variation of phase and the distribution, and
yet the low angles never fully recover (the death embrace of ground is
always there).

The ONLY deficit the vertical sees is in the characteristic Z of the
interface presenting a Brewster Angle that allows unfettered passage
of power through the interface and traps it. Again, it is the ratio
of the characteristic Zs that account for this. If you could contrive
to find an earth characteristic of 4000 Ohms instead of Salt Water's
40, then you would observe the EXACT SAME characteristics of
propagation. The poorest earth almost looks like the Z of the æther.
This means that the power impinging upon it is trapped (because ray
tracing would reveal it trying to penetrate the earth to re-emerge in
the antipodes). Hence the conduction explanation is a contrivance
that fits only through the imposition of a limited experience.

Replace the perfect conductor of an imaginary world with that of a
realistic earth and the Horizontal's low angle response still sucks to
the tune of 30dB down (for the terminally anal, perhaps closer to
-26dB). This says Horizontals suffer for the same reason irrespective
of earth conductivity (unless perhaps you are on a mile high mountain
of glass ). In some sense, this suggests that at least you don't have
to worry about it too much because there is nothing you can do about
it (although I have disproved this too).

On the other hand, for verticals, the variation of earth
characteristics gives rise to a wide variation in low angle response.
And for some earth characteristics, the vertical is clearly the winner
by an order of magnitude (dare I say in excess of one S-Unit?).

Is this boon conduction borne? If Salt water with a pathetic
conductivity orders of magnitude beneath nichrome wire is superb, then
by the facile logic of conductivity, we should see remarkable
performance boosts for a plain of silver. No, the conductivity
argument is simply the tales we tell frightened children who awake
from DX nightmares. ;-)

73's
Richard Clark, KB7QHC

Richard,

I am well aware of the properties of the phase reversal, cancellation of
direct and reflected waves, and so on. I have no substantive
disagreements with Terman.

I suspect Richard Clark was exercising a bit of poetic license by
stating that the horizontal polarization was "shorted" at the conducting
ground plane, perhaps in a vain attempt to simplify his explanation to
the original poster.

However, this statement is simply wrong. If it were true there would be
no NVIS nor any reflections at all from a normal incidence wave on a
conducting surface. Radar would not work. Mirrors would not work.

Wave cancellation is not such a difficult topic (except on RRAA). There
is no need to invoke phony arguments about waves "shorting".

73,
Gene
W4SZ

Richard Harrison wrote:
Gene, W4SZ wrote:
"---I was commenting on your assertion that the horizontal polarization
is "shorted out" at a conductive surfacce."

Richard Clark`s description may be indelicate but as I recall, Terman
says rouighly the same in several instances. Wish I had a copy at hand.
Terman says that a horizontally polarized low-angle wave suffers a phase
reversal upon reflection and as the difference in path length is
negligible between incident and reflected waves at low angles, the waves
being of opposite phase add to zero.

Best regards, Richard Harrison, KB5WZI

"Richard Clark" wrote

The electric dipole moment is clearly bridged by a conductor, by
definition. As such, at the interface, it must collapse completely
into a current which gives rise to counter emf, the two waves cancel
as a function of phase - the proof again is found in the Lambertian
distribution that vanishes completely with the removal of ground (why
horizontal antennas are held up in the air). The more remote the
ground, the greater the variation of phase and the distribution, and
yet the low angles never fully recover (the death embrace of ground is
always there).

Richard, would the dipole's performance thus be improved by bedding the
ground with sand, and hurt by adding ground radials? Same true if the dipole
was at some compromise between 1/4 wave and the desired 1/2 wave above
ground?

Regards,

Jack Painter
Virginia Beach, Va (where mostly sand exists anyway)