On Sun, 29 Aug 2004 09:31:13 +0000 (UTC), "Reg Edwards"
wrote:


"Richard Harrison" wrote -

There is no propagation of horizontally polarized groundwaves at
all. The low-angle reflected wave is out of phase with the incident
wave.

--------------------------------------------------------------

With a groundwaves there is no reflected wave and incident wave to get out
of phase with each other. By definition, it is all in the ground down to
one skin depth.

Reg, you are correct, of course, but Richard H. said above, "There is no
propagation of horizontally polarized groundwaves at all. The low-angle
reflected wave is out of phase with the incident wave."

What Richard mean't concerning the 'reflected' wave is that the energy radiated
downward from a horizontal antenna is reflected by the ground, and that
reflected wave is out of phase with the incident wave.

Walt, W2DU

Although a reflected horizontally polarized wave is out of phase with
the incident wave, and this explains the zero far field strength you get
with horizontally polarized waves, I'm not sure this is the relevant
explanation for the lack of ground wave propagation. The reason I doubt
it is that if you do the same analysis for vertically polarized waves,
you find that the net field strength is also zero at zero elevation
angle, except for the special case where ground is perfectly conducting.
So using the same analysis, you'd have to conclude that vertically
polarized waves can't propagate by ground wave, either.

Roy Lewallen, W7EL

Walter Maxwell wrote:
On Sun, 29 Aug 2004 09:31:13 +0000 (UTC), "Reg Edwards"
wrote:


"Richard Harrison" wrote -


There is no propagation of horizontally polarized groundwaves at
all. The low-angle reflected wave is out of phase with the incident
wave.


--------------------------------------------------------------

With a groundwaves there is no reflected wave and incident wave to get out
of phase with each other. By definition, it is all in the ground down to
one skin depth.


Reg, you are correct, of course, but Richard H. said above, "There is no
propagation of horizontally polarized groundwaves at all. The low-angle
reflected wave is out of phase with the incident wave."

What Richard mean't concerning the 'reflected' wave is that the energy radiated
downward from a horizontal antenna is reflected by the ground, and that
reflected wave is out of phase with the incident wave.

Walt, W2DU

Roy, W7EL wrote:
"So using the same analysis, you`d have to conclude that vertically
polarized waves can`t propagate by ground wave either."

I`ll turn to the authors for a source of my contention.

Terman says in his 1955 edition on page 803:
"The ground wave is vertically polarized, because any horizontal
component of electric field in contact with the earth is short-circuited
by the earth."

And on page 808, Terman says:
"Examination of these vector diagrams shows that with a perfect
reflector the horizontal components of electric field will exactly
cancel each other at the surface of the perfect conductor. In contrast,
the vertical components of the electric field of the incident and
reflected waves do not cancel, but rather add at the reflector surface
with small values of earth reflection angle."

Best regards, Richard Harrison, KB5WZI

Roy, W7EL wrote:
"So using the same analysis, you`d have to conclude that vertically
polarized waves can`t propagate by ground waves either."

Earth isn`t perfectly conductive but even so permits propagation of
vertically polarized waves.

Another expert, Kraus says on page 412 of his 1950 edition of
"Antennas":
"The electric field of a wave traveling along a perfectly conducting
surface is perpendicular to the surface....However, if the surface is an
imperfect conductor, such as the earth`s surface or ground, the
electric-field lines have a forward tilt near the surface.... Hence, the
field at the surface has a vertical component Ey and a horizontal
component Ex. The component Ex is associated with that part of the wave
that enters the surface and is dissipated in heat. The Ey component
continues to travel along the surface.

Best regards, Richard Harrison, KB5WZI

That's a much better explanation of the phenomenon of ground wave
analysis than the first one you put forth.

Roy Lewallen

Richard Harrison wrote:
Roy, W7EL wrote:
"So using the same analysis, you`d have to conclude that vertically
polarized waves can`t propagate by ground waves either."

Earth isn`t perfectly conductive but even so permits propagation of
vertically polarized waves.

Another expert, Kraus says on page 412 of his 1950 edition of
"Antennas":
"The electric field of a wave traveling along a perfectly conducting
surface is perpendicular to the surface....However, if the surface is an
imperfect conductor, such as the earth`s surface or ground, the
electric-field lines have a forward tilt near the surface.... Hence, the
field at the surface has a vertical component Ey and a horizontal
component Ex. The component Ex is associated with that part of the wave
that enters the surface and is dissipated in heat. The Ey component
continues to travel along the surface.

Best regards, Richard Harrison, KB5WZI

Roy, W7EL wrote:
"That`s a much better explanation of the phenomenon of ground wave
analysis than the first one you put forth."

True! Kraus was a much better explainer than I will ever be, I fear.

Best regards, Richard Harrison, KB5WZI