Walter Maxwell, W2DU wrote:
"At this height above ground (0.35 wavelength) the dipole is spaced 0.7
wavelength from its image in the perfect ground plane."

I accept that, but cannot reconcile page and figure numbers. I have only
the 1950 and 2003 editions of "Antennas". They are prticeless to me
though I`m not as familiar with them as I am with Terman.

I suggested determining ground resistance by the attenuation it adds to
the ground wave. I neglected to say that the time to do so would be when
sky wave propagation was small to none. Midday when using medium wave
signals for signal strength measurements unless the measurement sites
were close enough to the transmitter to make sky wave unimportant. I
used to make medium wave broadcast station monitoring point field
strength measurements within a few miles from the station, daytime,
nighttime, or anytime because at this short range there is no chance of
sky wave interference. You would be much more considerate of the time of
day 200 miles from the station. If HF signal attenuation versus distance
from the transmitter is used to determine earth resistance, for
practical purposes ground wave propagation is nearly negligible,
especially at the high end of the HF spectrum. I believe B, L, and E.
used 3 MHz which produces some ground wave.

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote in message
...
Walter Maxwell, W2DU wrote:
"At this height above ground (0.35 wavelength) the dipole is spaced 0.7
wavelength from its image in the perfect ground plane."

I accept that, but cannot reconcile page and figure numbers. I have only
the 1950 and 2003 editions of "Antennas". They are prticeless to me
though I`m not as familiar with them as I am with Terman.

I suggested determining ground resistance by the attenuation it adds to
the ground wave. I neglected to say that the time to do so would be when
sky wave propagation was small to none. Midday when using medium wave
signals for signal strength measurements unless the measurement sites
were close enough to the transmitter to make sky wave unimportant. I
used to make medium wave broadcast station monitoring point field
strength measurements within a few miles from the station, daytime,
nighttime, or anytime because at this short range there is no chance of
sky wave interference. You would be much more considerate of the time of
day 200 miles from the station. If HF signal attenuation versus distance
from the transmitter is used to determine earth resistance, for
practical purposes ground wave propagation is nearly negligible,
especially at the high end of the HF spectrum. I believe B, L, and E.
used 3 MHz which produces some ground wave.

Best regards, Richard Harrison, KB5WZI

Richard, I don't understand why you can't reconcile the Page numbers. I have the
same editions of Kraus as you, but the edition of Kraus I'm referencing is
the1950, the same as yours.

Walt

Walter, W2DU wrote:
"Richard, I don`t understamd why you can`t reconcile the page numbers."

I don`t understand either, but it may be blindness and senility. Now,
I`ve found everything fight where Walt said it would be!

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote in message
...
Walter, W2DU wrote:
"Richard, I don`t understamd why you can`t reconcile the page numbers."

I don`t understand either, but it may be blindness and senility. Now,
I`ve found everything fight where Walt said it would be!

Best regards, Richard Harrison, KB5WZI

Richard, that's called a 'senior moment'. Except when I do it they tell me it's
my Alzheimer's Syndrome raising its ugly head.

Walt

"Walter Maxwell" wrote
Richard, that's called a 'senior moment'. Except when I do it they
tell me it's
my Alzheimer's Syndrome raising its ugly head.

=====================================

I too am afflicted with Alzheimer's. I forget what I said at the
beginning of a vocal sentence before I get to the end. Also I have
recently had a very minor stroke which has affected the small and next
fingers of my left hand. This has slowed down my keyboard dexterity.

But it's quite normal for my time of life and it doesn't worry me.
Least of all does KB7QHC's lying slander worry me.
----
Reg, G4FGQ

On Tue, 21 Jun 2005 23:42:45 +0000 (UTC), "Reg Edwards"
wrote:

Least of all does KB7QHC's lying slander worry me.

I love you too, Reg. Thanx for taking the time to acknowledge me.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Tue, 21 Jun 2005 23:42:45 +0000 (UTC), "Reg Edwards"
wrote:

Least of all does KB7QHC's lying slander worry me.

I love you too, Reg. Thanx for taking the time to acknowledge me.

73's
Richard Clark, KB7QHC

Lying slander is a redundancy, isn't it? Just the opposite of sanitary sewer as
an oxymoron. I've been enjoying Richard's redundancy and Punchinello's responses
immensely.

Walt, W2DU

Walter Maxwell, W2DU proposed a fast way to determine earth loss at
radio frequencies without digging into the earth.

"Earth Constants", conductivity and permittivity, affect ground wave
propagation and terrestrial reflections.. They may predict or explain
some propagation. They al;so affect operation of nearby antennas.

Earth permittivity is the ratio of a capacitor`s capacitance using an
earth sample as a dielectric, to its capacitance using air as the
dielectric. Under "permittivity" my dictionary says: "-See Dielectric
Constant.".

Earth conductivity is defined as the conductance between opposite faces
of a unit cube (usually 1.0 cubic meter) of a given earth material, e.g.
rock, sand, clay, loam, water, etc. Hoe do you measure this without
changing its value?

Conductivity and permittivity are affected by chemical and physical
composition, moisture, and temperature (especially freezing).

Earth constants are functions of frequency and antenna polarization.
R.F. determination seems best.

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote

Earth constants are functions of frequency and antenna polarization.
R.F. determination seems best.

=================================

You seem to know something about it Rixhard.

How is it done?
----
Reg

Reg, G4FGQ wrote:
"How is it done?"

We have to do it within the USA broadcast frequencies with the following
method.

The site of the transmitting antenna is plotted on a very accurate map.

Pick map sites along radiaal lines from the antenna which are accessible
and free from possible reradiation sources (hard to do within a city)
but many sites along a radial will work.

For a single-tower, the nearest measurement site should be at least 5x
the tower height away. For a directional array, the nearest measurement
site should be at least 10x the widest gap between towers in the array.
You need to be far enough away so the antenna system appears to be a
point source.

You need to make a log of the measurements you make, showing the site
distance from the transmitter, measured field strength, time and
conditions which influence the measurement. You need to be able to
duplicate the measurements. You would prefer to make the first set of
measurements with the antenna operating in a nondirectional mode even if
it normally does not operate nondirectionally, so you can determine
efficiency very simply.

The more sites and measurements, the better. 25 measurements along each
radial is often considered enough for a nondirectional antenna. 40 or 50
would be required 9in a directional array, as the number of radial
measurements needed depends on the complexity of antenna system and its
pattern.

After completing measurements along a single radial, they should be
analyzed to determine the effective field at one mile from the antenna,
and the effective ground conductivity.

Fortunately, the FCC publishes charts are made a part of the rules in
Part 73 of the FCC Rules. You have likely seen reproductions in many
textbooks. I have an old copy of all the groundwave field intensity
versus conductivity charts which divide the AM broadcast band into
frequency segments.

These FCC charts contain more information than we can use, but they also
have what we need.

At the top of the chart is a straight line that shows how the signal
would be attenuated over perfectly conducting earth. The field strength
value at one mile is 100 mV / m. At 2 miles, it`s 50 millivolts / m, and
so on. This is as expected as over perfedt earth the signal varies
inversely with distance from the transmitter.

Beliw the straight line on the chart is a family of curves, each
dedicated to a particular soil conductivity. There is a curve for sea
water, 5.000 millisiemens (millimhos) and there is a curve for about as
nonconductive soil as is found (0.5 millisiemens), and there are several
curves in between those extremes.

All of the FCC curves are based on 100 mV / m at 1 mile, but can be
scaled. If your transmitter delivers 500 mV / m at 1 mile, aimply
multiply all points on the curve by 5.

We want to find the conductivity of our earth. It can be different on
every radial parh from the antenna.We find conductivity by plottibg our
measured field intensities on translucent graph paper with grid lines
which match the fcc graph. Then we line them up and place them over a
light source. We can see which of the FCC curves our points most closely
follow. It`s labeled ewith its conductivity.

Best regards, Richard Harrison, KB5WZI