Anecdotally, I have noticed, I have no problem working Europe, ZS, VK, and
ZL on 75 running 90 watts. I am typically 5-9 or better in to Great Britain.
My antenna is 38 feet in the center and 20 feet on both ends. Actually I
have two 132 foot dipoles that are orientated 90 degrees from each other.
They share a common relay box for switching in additional ladderline. That
is the input to the relay box is selected by a separate relay. The unused
antenna is grounded. I have tried it both grounded and ungrounded and it
"seems" to be better when the unused antenna is grounded.

My next set of relays will tie them both together as a big capacity hat on
160. Have not got around to doing it yet.

I can push a 10 foot ground rod into the ground by hand. If I don't wet it
down, I can rotate it by hand when it is 9.75 feet in the ground. If a
rabbit gets in the garden, one is in dire straits trying to find a rock to
throw at it.

A sand pit down the road from me is over 200 feet deep and they have not hit
anything other than sand in over 20 years of digging.





"Roy Lewallen" wrote in message
...
Fred W4JLE wrote:
It would be interesting to recreate the measurements at other locations.
My
location has 500 feet of sand below me. It would be a great improvement
just
to have poor soil.

Depends on your objective. For NVIS operation with a horizontal antenna,
where you need the reflection, that's probably true. But for a vertical
or for DX with a horizontal antenna, you're better off with the sand.
Perfect ground has no loss; free space has no loss. There's an
intermediate quality of ground at which the loss is maximum at a given
frequency. Unfortunately, this happens to be in the range of ordinary
ground characteristics in the HF range. Your ground should be very low
loss. And your pattern should resemble free space, with a very strong
field at very low radiation angles.

Roy Lewallen, W7EL

Walter Maxwell, W2DU wrote:
"Do you think any soil characteristics could be determined by such
data?"

Kraus has an interesting figure, No. 11-20 on page 305 of his 1950
edition of "Antennas". It is the feedpoint resistance versus height in
wavelengths over perfect ground (a copper sheet?) of a resonant 1/2-wave
dipole.

It varies from zero ohms at zero height to a maximum of about 100 ohms
at 0.35 wavelength above ground. The resistance settles down to just
above 70 ohms at infinite height (free space radiation resistance
value).

Clean dry sand may be a very good insulator. If it were deep enough, a
dipole lain on it might have a feedpoint of about 70 ohme. Better soil
conductivity might shift the drivepoint of the dipole to a lower
resistance as the Kraus figure indicates for perfect ground next to the
dipole.

Several measurements at slightly different locations and times may need
to be made and averaged for reliable results. The curve in Fig. 11-20
oscillates around the free space radiation resistance so that at some
altitudes feedpoint resistance goes down as altitude increases. One
would need to know which part of the curve the measured resistance fell
upon.

Walt may be on to something with his method for determining earth
constants. There are so many broadcast stations in the USA that soil
conductivity has been already determined in nearly all areas. For
unknown areas, one could lay out radial paths from existing stations and
measure feild strengths along the radial at several places and see how
much more attenuation there is versus the "unattenuated" values expected
and determine average ground conductivity by the loss added by the
ground.

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote in message
...
Walter Maxwell, W2DU wrote:
"Do you think any soil characteristics could be determined by such
data?"

Kraus has an interesting figure, No. 11-20 on page 305 of his 1950
edition of "Antennas". It is the feedpoint resistance versus height in
wavelengths over perfect ground (a copper sheet?) of a resonant 1/2-wave
dipole.

It varies from zero ohms at zero height to a maximum of about 100 ohms
at 0.35 wavelength above ground. The resistance settles down to just
above 70 ohms at infinite height (free space radiation resistance
value).

Clean dry sand may be a very good insulator. If it were deep enough, a
dipole lain on it might have a feedpoint of about 70 ohme. Better soil
conductivity might shift the drivepoint of the dipole to a lower
resistance as the Kraus figure indicates for perfect ground next to the
dipole.

Several measurements at slightly different locations and times may need
to be made and averaged for reliable results. The curve in Fig. 11-20
oscillates around the free space radiation resistance so that at some
altitudes feedpoint resistance goes down as altitude increases. One
would need to know which part of the curve the measured resistance fell
upon.

Walt may be on to something with his method for determining earth
constants. There are so many broadcast stations in the USA that soil
conductivity has been already determined in nearly all areas. For
unknown areas, one could lay out radial paths from existing stations and
measure feild strengths along the radial at several places and see how
much more attenuation there is versus the "unattenuated" values expected
and determine average ground conductivity by the loss added by the
ground.

Best regards, Richard Harrison, KB5WZI

Richard, your indication that the dipole input resistance of 100 ohms at 0.35
wavelength above ground is interesting, in that if you look at Kraus' graph of
mutual impedance of parallel side-by-side radiators in his Fig 10-12, Page 266,
you can see the reason for this.

At this height above ground the the dipole is spaced 0.7 wavelengths from its
image in the perfect ground plane. The mutual resistance at this spacing
is -24.8 ohms, as shown in Fig 10-12 and in Table 10-1 on Page 267. Table 10-1
also shows the self resistance minus the mutual resistance at this spacing to be
97.9 ohms. There is the approximate 100 ohms shown in the graph of Fig 11-20.
Note that 97.9 - 24.8 = 73.1 ohms, the nominal resistance of a thin half-wave
dipole in space.

Of course this data relates only to the condition of perfect ground, with total
reflection and no attenuation. I would hope that the delta R and delta X values
vs height taken from my measured data might shed some light on the ground
conductivity and permittivity under my antenna. My soil is very sandy. Knowing
that, the delta values might show some tendency to verify that condition.

Walt, W2DU

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 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

"Walter Maxwell" wrote
You've presented a very interesting way of measuring soil
characteristics. When
I return to Florida in November I'm going to use your method of
measuring the
soil underneath the dipole

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

Walt, would it be possible for somebody to go to B.L & E's original
site and measure the soil charateristics which they completely forgot
all about. Presumably, they were not aware that the type of soil had
any effect on their measurments. At what time of the year did they
conduct their famous experiments?

Pity we shall have to wait till November for you to re-visit Florida.
In view of the high temperature coefficient of soil resistivity and
probability on permittivity, don't forget to take a thermometer.

What was the soil temperature when you made your HF measurements
versus height? Soil temperate discrepancies might be of greater order
and swamp the effects of considerable changes in antenna height.

But I suggest we are more interested in change of antenna impedance
versus height above ground than we are in apparent change in soil
characteristics versus frequency.
----
Reg, G4FGQ

Reg Edwards wrote:

Walt, would it be possible for somebody to go to B.L & E's original
site and measure the soil charateristics which they completely forgot
all about. . .

But what would that tell us about the soil conditions to, say, three
skin depths -- or even one? What conclusions could we draw from that
information?

Roy Lewallen, W7EL

Reg Edwards wrote:

Walt, would it be possible for somebody to go to B.L & E's
original
site and measure the soil charateristics which they completely
forgot
all about. . .

But what would that tell us about the soil conditions to, say, three
skin depths -- or even one? What conclusions could we draw from that
information?

Roy Lewallen, W7EL

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

None, except that you are nit-picking as usual.

And that B, L & E, all three of them, were floundering about in an
amateurish fashion.

Yet it had been well known to others for 35 years that soil
conductivity and permittivity had a profound effect on ground wave
propagation.

All they had demonstrated was that 113 radials was more than
sufficient for MF and low HF broadcast propagation which was what
everybody already knew.

And so the rounded-up, Marzipan the Magician, magic number of 120 got
stuck in the bibles. A typical American way of going about things. ;o)
----
Reg.

Reg Edwards wrote:

[Responding to the question of what useful information could be obtained
from measuring the surface soil conductivity at the B, L, and E site]

None

But I'm sure that won't stop you from your frequent complaints that they
"forgot" to measure it. I see you've found other things to criticize,
though. . .

, except that you are nit-picking as usual.

Asking what use it would be to measure the surface conductivity (as you
suggested) is nit-picking? You have a strange way of evaluating things.

And that B, L & E, all three of them, were floundering about in an
amateurish fashion.

Ah, you play the role of armchair quarterback very well. Sure is too bad
you didn't think of doing the experiment in 1937 -- I'm sure you would
have done it right. All AM broadcast stations would be using precisely
100, not 120 radials, and we'd know the surface ground conductivity of
the measurement field (but still wouldn't know what to do with the
information). The Reg of '05 would have the warm, satisfied feeling of
knowing that another seminal piece of work was done by one of Her
Magisty's loyal subjects (or was it His Magisty in '37 -- I forget)
instead of the gnawing aggravation he experiences thinking that some
American ruffians might actually have done something useful. Life would
sure be a lot better today, wouldn't it?

Yet it had been well known to others for 35 years that soil
conductivity and permittivity had a profound effect on ground wave
propagation.

Propagation, yes. But nobody had a good handle of the effect of ground
systems on antenna efficiency until their experiments.

All they had demonstrated was that 113 radials was more than
sufficient for MF and low HF broadcast propagation which was what
everybody already knew.

You obviously haven't read the paper. It has nothing at all to do with
propagation.

And so the rounded-up, Marzipan the Magician, magic number of 120 got
stuck in the bibles. A typical American way of going about things. ;o)
----

Boy, it really must hurt deeply to think that some Americans did
something that the rest of the world considers to be pioneering. Have
some more wine -- it'll dull the pain.

But under no circumstances should you actually stoop to reading the
paper you're so fond of criticizing. It would just make you feel worse.

Reg.

Roy Lewallen, W7EL
certified Reg's Old Wife -- and inveterate nit-picker