Walter Maxwell wrote:
. . .
One of the reasons I offered to distribute the data from my
measurements is to see whether anyone can deduce any soil
characteristics from the changes in impedance with height. The
changes are significant. For example, the terminal impedance with the
dipole on the ground runs from 470 + j250 at 14 MHz to 570 + j132 at
15 MHz. The inductive reactance doesn't become capacitive until the
dipole is 2 ft off the ground. In addition, except at zero height,
the resistance component decreases with height, but for every height
the resistance increases with frequency. Do you think any of the soil
characteristics could be determined by such data?
. . .

I haven't looked into this carefully, but one person I know who was very
involved in NVIS operation (where ground characteristics are important)
tried it some years ago. He concluded that it wasn't possible to
set the antenna height and make measurements with sufficient accuracy to
infer the ground characteristics with any confidence.

Roy Lewallen, W7EL

On 20 Jun 2005 11:36:28 -0500, wrote:

A simpler method that avoids all the digging and repacking of
the soil is described at

http://www.antennasbyn6lf.com/2005/0...arameter_.html

I've been meaning to try it at my qth this summer.

Hi Torsten,

Another attractive solution of one datum trying to solve a
multivariate problem.

On review of the material offered at this link above, I find that its
"Figure 2, widely used graph of conductivity versus frequency for
various soils" is in brutal conflict with other published material.
The inscription of "transition frequency" reveals such examples that
are off from the data inflections by orders of magnitude. Further,
there is no citation for where this figure was lifted (and there is
evidence of doctoring, if only to erase the original figure number).

The data in "Table 1, 18" monoprobe, Co = 7.41 pF. On my antenna hill
with an AEA-CIA analyzer" also reveals a curious condition that is
nearly equal to swamp-like conditions in its Q evaluations, and yet
showing almost no frequency variation nearly equal to desert like
soil.

The graph, "Figure 10, Comparison of Er between two sites" reveals
that the Hill site has a soil condition equal to Fresh Water at 1 MHz.
It then plunges to a "Very Wet Soil" condition at 8 MHz (curious thing
about this, is that earlier data did not show any frequency variation
in Q). The Rose Garden site, again, showed very swamp like
conditions. This is a very exceptional region of the country, to say
the least. I've seen only one example in fiction: Dilbert's visits to
Elbonia where every one lives in waist deep mud.

In graph, "Figure 11, soil conductivity with and without grass cover
using an 18" monoprobe," is presented data that is inverse
relationship to published data. But this, too, is (in)consistent with
other material presented at the link provided.

This goes on and on - to the neglect of confirmation against the
numerous references cited (without corresponding discussion nor
tie-in).

There is a wealth of data and information, but given it does not agree
with other published data, it appears to suffer from a poverty of
correlation. The simple numbers revealed as conductivity, di-electric
constants and the Q relationships; if used as sanity checks, says that
precision and accuracy in measurements does not redeem this analysis.

Something is very seriously in error: either my reading, or the
material offered.

73's
Richard Clark, KB7QHC

Roy, W7EL wrote:
I haven't looked into this carefully, but one person I know who was very
involved in NVIS operation (where ground characteristics are important)
tried it some years ago. He concluded that it wasn't possible to
set the antenna height and make measurements with sufficient accuracy to
infer the ground characteristics with any confidence.

Roy Lewallen, W7EL

Understood, Roy, but was this person saying that with just one height it
wouldn't give sufficient accuracy, or is he saying that with impedance knowledge
at many different heights there would still be no determination of any of the
ground characteristics?

Would you not like to see my data before concluding it couldn't reveal any
ground characteristics.?

Walt

On Mon, 20 Jun 2005 16:21:58 -0400, "Walter Maxwell"
wrote:
Understood, Roy, but was this person saying that with just one height it
wouldn't give sufficient accuracy, or is he saying that with impedance knowledge
at many different heights there would still be no determination of any of the
ground characteristics?

Hi Walt,

And per my several critiques into this matter, all such broad
proclamations lack the fundamental of drawing a validation through
correlating work in the subject. Let's examine the one point offered:
He concluded that it wasn't possible to
set the antenna height and make measurements with sufficient accuracy to
infer the ground characteristics with any confidence.
This, of course, presumes that this source has any actual
authoritative data. Something that is prohibitively beyond the scope
of an individual to determine (when it is already rejected through
correlations of antenna characteristics and measurements) in the first
place suggests there is none.

Roy has already pointed out the futility of a piece-wise measurement
throughout the bulk of earth soaked by RF to its skin depth. I have
pointed out that these several treatments offered only go to the thin
veneer of soil. Some conclusions drawn were preposterous on the face
of the data offered. Further, to suggest the four lead measurement be
stretched to employing wavelength sized leads is fraught with error
through the denial of those leads becoming what every Amateur already
has, an antenna.

Reg has dismissed the use of an antenna to measure the earth's
contribution of loss, or to distinguish its characteristics by
perturbing the known characteristic of an antenna. Such dismissal is
not an argument - it is a conceit.

Walt, your data is comprehensive enough to build a soil model for the
band you studied. I seriously doubt anyone could challenge your
results if they were internally consistent.

73's
Richard Clark, KB7QHC

Walt, your data is comprehensive enough to build a soil model for the
band you studied. I seriously doubt anyone could challenge your
results if they were internally consistent.

73's
Richard Clark, KB7QHC

Thanks Richard, you've made my day!

Walt

Dick,

PHOOEY !

88, Punchinello

On Mon, 20 Jun 2005 21:48:28 +0000 (UTC), "Reg Edwards"
rustling his apron wrote:
Dick,
PHOOEY !

Yeah, but you heard it from me first. :-0

Walter,

What people want to know is how soil constants change with frequency.

Measurements at one frequency will tell you nothing about that.

Yes please, send me a copy of your test results. But I can't
guarantee receiving anything attached to an e-mail. My computer is
playing games. Can you send it AS an e-mail.
----
Reg.

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

"Walter Maxwell" wrote in message
...

Walt, your data is comprehensive enough to build a soil model for
the
band you studied. I seriously doubt anyone could challenge your
results if they were internally consistent.

73's
Richard Clark, KB7QHC

Thanks Richard, you've made my day!

Walt

PHOOEY !

Yeah, but you heard it from me first. :-0

============================
You are not so clever.

You didn't detect my deliberate mistake.

Ah well, I suppose I shall have to tell you.

Soil constants are not constant.

Wanna make a bet you don't have the last say?

Punchinello

Walter Maxwell wrote:
Roy, W7EL wrote:

I haven't looked into this carefully, but one person I know who was very
involved in NVIS operation (where ground characteristics are important)
tried it some years ago. He concluded that it wasn't possible to
set the antenna height and make measurements with sufficient accuracy to
infer the ground characteristics with any confidence.

Roy Lewallen, W7EL


Understood, Roy, but was this person saying that with just one height it
wouldn't give sufficient accuracy, or is he saying that with impedance knowledge
at many different heights there would still be no determination of any of the
ground characteristics?

I interpreted what he said as meaning that he looked into the method and
determined it wasn't practical. Surely he thought of making numerous
measurements. He's a very capable engineer, so I took what he said at
face value. On the other hand, I don't think he's highly skilled in
making precision antenna measurements, so he might have assumed that a
level of accuracy wasn't achievable which in fact might be.

You might spend a little while with EZNEC looking at how much a change
in ground conductivity or permittivity changes the antenna input Z at
various heights, and how much the height changes the Z with a given set
of ground characteristics. Then consider whether you'd be able to set
the height and make the impedance measurements accurately enough to
infer the ground characteristics with any degree of confidence.

Would you not like to see my data before concluding it couldn't reveal any
ground characteristics.?

I'd like to see your data, but it wouldn't be enough information to
conclude whether the method would be practical or not.

Roy Lewallen, W7EL