"Walter Maxwell" wrote
Reg asked if I could send my data as an email, so I converted the
file to text
format to be able to present the data in full here in this msg.

I checked to see that the tabular format remained intact, and it did
in Outlook
Express, so here it is. I hope the tabular format will remain intact
in your
browsers. Be sure to give your screen maximum width. If it doesn't,
let me know
and I'll resend in PDF format.

Walt, W2DU

Dipole Terminal Impedance Data Obtained From Measurements at Various
Heights
Above Ground in the Frequency Range from 14.0 to 15.0 MHz.
Measurements Made be
W2DU at the W2DU site in DeLand, Florida.
============================================

Data received as an extension to this message. Fills screen very
nicely.

Thank you very much Walter for your trouble.
----
Reg, G4FGQ

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

"Wes Stewart" wrote in message
...
On Tue, 21 Jun 2005 11:37:57 -0400, "Walter Maxwell"
wrote:

[snip]

Walt,

Your's was a particularly heroic effort and I commend you for it.

I have taken the data you supplied in text form, converted it to comma
separated values (csv) and imported it into XLZIZL where I can use
your measured input values, add the two different transmission lines
that you used and compute the load resistance at the antenna.

I know that you supplied these results, but I find slightly different
answers and I believe the reason is as follows:

I'm guessing that you calibrated your two lines as one. If I'm wrong,
slap me upside the head.

Depending on the exact type, RG58(x) has slightly different Zo values.
RG141 is specified as 50.0. Your Zo of 54 and your phase constant
suggest a Vp of slightly less than .66, which is remarkably close to
specification, but slightly low, considering the ~5% (2', RG141) of
your composite line has Vp ~ 0.7.

This is really getting fussy, but I'm beginning to believe that to
possibly make a determination about ground characteristics based on
antenna Z measurements, the measurements are going to have to be very
precise.

Wes

You're right, Wes, I calibrated the composite line as one line. And I agree that
if you calibrate them separately a small difference in the results will be
obtained. But I believe the difference will be insignificant. Consider this: The
nominal Zo of RG58 is 55 ohms and that of RG141 is 50, as you point out. The
measured Zo of the composite line is 54 ohms. Now also consider this: The
nominal vf for RG58 is 0.659 and for RG141 is 0.695. Thus the difference in the
nominal Zo is 10% and the difference in vf is 5.5%, but the length of the short
portion is only 5% of the total length. From these small differences I presumed
the error would be significant. You didn't say exactly how much difference you
found, or the procedure you used to determine it.

So I made the following calculations from the data where the height is 10 ft at
14.55 MHz:
First transforming the measured input impedance through the 40 ft of RG58, and
then transforming the impedance found at the load end of the RG58 through the 2
ft of RG141. The results are as follows:

At the load end of the RG58 and the input to the RG141: 69.41 - j19.19,
At the load end of the RG141: ........................................79.23 -
j3.25.

At the load end of the RG141 using the composite data: 81.21 - j1.25.

The difference in the R values is only 1.98 ohms and in the X values is only 2
ohms. I consider this degree of error insignificant. Would you not agree?

Walt

On Mon, 20 Jun 2005 23:17:40 -0400, "Walter Maxwell"
wrote:

I'd like to hear your comments.

Hi Walt,

On first pass, the results are fairly consistent, but with two
exceptions. I am not sure if this is in my translation to file
formats suitable for Mathcad, or if they lie in your process.

Anyway, a general description:

The granularity of 50Khz appears to not be fine enough to find all
peak resonances for the 9 of the 11 within the band. I have rendered
the data into a sequence of 11 curves (one curve for each height) I
call "Q" where that quality factor relates to the ratio of RL to |XL|.
This was merely a survey to glance at all the data at once and to
observe how the Mathcad sheet was taking shape. To this point this
could as easily be accomplished in Excel. Continuing, I noted that
two sets of height data moved retrograde to the general trend.

That general trend revealed a family of peaks that moved up-frequency
as the antenna height was raised. Two of the peaks were out of the
band. One was above the band (the lowest antenna height) and the
second was below the band (the second lowest antenna height). Of
these two, I would suspect that the first, or lowest antenna height,
was a curve rising to peak at the second (anti)resonance - otherwise,
the trend is progressive with two exceptions.

Those exceptions are found in raising the antenna from 8' to 10' and
from 14' to 16'. The peaks in each of these step changes move counter
to the trend: down-frequency when the height is raised. Again, this
may be entirely a transcription error of my own that I need to
investigate further.

The biggest frequency shift comes with (this is a presumption) lifting
the antenna up off the ground to the one foot level. The next biggest
shift comes with the elevation change to the two foot level - and so
on with progressively smaller shifts in frequency shift and
progressively sharpening of the curves as the antenna is hiked higher.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Mon, 20 Jun 2005 23:17:40 -0400, "Walter Maxwell"
wrote:

I'd like to hear your comments.

Hi Walt,

On first pass, the results are fairly consistent, but with two
exceptions. I am not sure if this is in my translation to file
formats suitable for Mathcad, or if they lie in your process.

Anyway, a general description:

The granularity of 50Khz appears to not be fine enough to find all
peak resonances for the 9 of the 11 within the band. I have rendered
the data into a sequence of 11 curves (one curve for each height) I
call "Q" where that quality factor relates to the ratio of RL to |XL|.
This was merely a survey to glance at all the data at once and to
observe how the Mathcad sheet was taking shape. To this point this
could as easily be accomplished in Excel. Continuing, I noted that
two sets of height data moved retrograde to the general trend.

That general trend revealed a family of peaks that moved up-frequency
as the antenna height was raised. Two of the peaks were out of the
band. One was above the band (the lowest antenna height) and the
second was below the band (the second lowest antenna height). Of
these two, I would suspect that the first, or lowest antenna height,
was a curve rising to peak at the second (anti)resonance - otherwise,
the trend is progressive with two exceptions.

Those exceptions are found in raising the antenna from 8' to 10' and
from 14' to 16'. The peaks in each of these step changes move counter
to the trend: down-frequency when the height is raised. Again, this
may be entirely a transcription error of my own that I need to
investigate further.

The biggest frequency shift comes with (this is a presumption) lifting
the antenna up off the ground to the one foot level. The next biggest
shift comes with the elevation change to the two foot level - and so
on with progressively smaller shifts in frequency shift and
progressively sharpening of the curves as the antenna is hiked higher.

73's
Richard Clark, KB7QHC

Very interesting, Richard. I made a cursury check on the retrograde data, and it
seems that the trend is in the original measured data. I compared readings of
adjacent frequencies for two different heights where the retrograde occurs and
found differences in original R values that I can explain only in the
possibility of different degrees of soil wetness, because the measurements were
not all taken on the same day. The date of each measurement is in the upper left
corner of each page. Since the measurements were taken 22 years ago I can't
remember whether I logged the rain vs non-rain days, and the original data is in
obscure files in Florida. I would not have taken measurements during a rain, but
the day after a rain the soil would still have been wetter than the day before
the rain. Wetness is the only explanation I can think of for the jerk in the
data.

Are your Mathcad graphs in a format suitable for emailing? If so, I'd like to
see them.

Walt

"Reg Edwards" wrote in message
...

"Walter Maxwell" wrote
Reg asked if I could send my data as an email, so I converted the
file to text
format to be able to present the data in full here in this msg.

I checked to see that the tabular format remained intact, and it did
in Outlook
Express, so here it is. I hope the tabular format will remain intact
in your
browsers. Be sure to give your screen maximum width. If it doesn't,
let me know
and I'll resend in PDF format.

Walt, W2DU

Dipole Terminal Impedance Data Obtained From Measurements at Various
Heights
Above Ground in the Frequency Range from 14.0 to 15.0 MHz.
Measurements Made be
W2DU at the W2DU site in DeLand, Florida.
============================================

Data received as an extension to this message. Fills screen very
nicely.

Thank you very much Walter for your trouble.
----
Reg, G4FGQ

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

Fine, Reg, I hope you find the data of interest.

Walt

On Wed, 22 Jun 2005 15:31:07 -0400, "Walter Maxwell"
wrote:

Wetness is the only explanation I can think of for the jerk in the
data.

Oh, where that comment might lead. :-)

Are your Mathcad graphs in a format suitable for emailing? If so, I'd like to
see them.

Hi Walt,

Sure, I will kit that up later today.

73's
Richard Clark, KB7QHC

On Wed, 22 Jun 2005 15:31:07 -0400, "Walter Maxwell"
wrote:

I compared readings of
adjacent frequencies for two different heights where the retrograde occurs and
found differences in original R values that I can explain only in the
possibility of different degrees of soil wetness, because the measurements were
not all taken on the same day.

Hi All,

This is a life's lesson in the value of context and measurement, as
well as in the discipline of taking notes. Walt's memory suggests a
reason for the perturbation observed in the data, and it is not
unreasonable. I would suggest that there is some (however slight)
likelihood that the correlations may be backwards in that most of the
days followed rain, and these perturbations were on dry days.

Before or after is not the issue. Before or after is a matter of
separability which is more important. With analysis, Walt's
conjecture can be tested against the data and what it reveals about
the impact the ground's proximity had on the antenna.

His data, either way, already supports that ground is measurable
within the data that falls outside of the spread of noise and error.
Even if Walt slipped an instrument reading or injected statistical
noise, he did it so consistently that he was always in error in the
same direction (this is called systematic error). This may impact the
accuracy of the final answer, but it does not impact the thesis'
general conclusion. What is more, even if such mischance occurred
(and I doubt it), it is recoverable with one or several cardinal
measurements to correct the earlier bias.

This round of discussion also reveals that bad data is as good as good
data. Those who discard results and tailor their reports stand a good
chance of not discovering how to fix their problems when they are
shown to be in serious error (which is to say they probably rejected
good results). I pointed this threat out in another thread that
linked to exhaustive ground data that showed hills composed of fresh
water.

73's
Richard Clark, KB7QHC

Ian White wrote:
"The real technical question is how many, and how long, will be "just
enough" for "here"?"

Reminds me of the trailer house designer pulling out reaces until the
whole projkect collapses, then rebuilding with only the last brace
removed reinstalled.

You don`t need any radials with a horizontal dipole. Broadcasters are
launching ground waves to reach a local audience. Amateurs may want ro
reach DX with sky waves.
For radials under an earth mounted vertical, there`s no magic number or
length. You can add to the count until resistance elimination fades. You
can lengthen them until the current at their tips is almost zero. Or,
you can just decide how much you will spend on wire. I read that
quantity of radials is better than longer radials.

If you want some idea of how conductive soil is, I read that a Variac,
ground rods , ammeter and voltmeter is the way to go. Adjust current
between the rods to one ampere with the Variac. Resistance between the
rods is then the volts between them.

Terman has already supplied Table 22-1 "TYPICAL GROUND CONSTANTS" on
page 308 of his 1955 edition for estimating dielectric constant and
ground conductivity.

At high frequencies, poor ground conductivity takes eome energy from the
reflected wave and the combined direct and reflected wave can`t be a
complete cancellation. The direct wave alone is stronger than its
combination with an out of phase wave. Ground wave propagetion fades in
a short distance at high freqiuencies. So what use does the DXer have
for soil conductivity? Isn`t something like Terman`s Table good enough,
unless he is considering laying his antenna on or near the soil?

Best regards, Richard Harrison, KB5WZI

Walter Maxwell wrote:

Hasn't the copyright expired on material published in 1937?

Hm. The way I read http://www.copyright.gov/circs/circ1.html#hlc, it
has. It looks to me like the original copyright was good for 28 years
and for copyrights originally issued in 1937, renewal (if done) was good
for another 28. That would put it in the public domain after 1993. I'd
sure appreciate comments from someone who's actually familiar with the
law -- it's pretty convoluted and I'm not at all confident about my
interpretation.

Roy Lewallen, W7EL

On Wed, 22 Jun 2005 16:13:55 -0700, Roy Lewallen
wrote:

Walter Maxwell wrote:

Hasn't the copyright expired on material published in 1937?

Hm. The way I read http://www.copyright.gov/circs/circ1.html#hlc, it
has. It looks to me like the original copyright was good for 28 years
and for copyrights originally issued in 1937, renewal (if done) was good
for another 28. That would put it in the public domain after 1993. I'd
sure appreciate comments from someone who's actually familiar with the
law -- it's pretty convoluted and I'm not at all confident about my
interpretation.

True it gets very complicated, especially when the likes of Disney get
an act through Congress to copyright Mickey Mouse forever.

http://writ.news.findlaw.com/comment..._sprigman.html

Unfortunately, the Supreme Court was not interested in the
constitutional aspects of this monstrosity and let it stand.

The average citizen can afford to bribe his local officials (democracy
in action), but when it comes to Congress, you need real money.

Publish the paper Walt, the authors are all gone (I think, but you
know better than I) the IRE is gone too; what are they going to do,
come back from the grave and sue you?