"Walter Maxwell" wrote in message
...

"Roy Lewallen" wrote in message
...
Ian White GM3SEK wrote:

. . .
The real technical question is: how many, and how long, will be "just
enough" for "here"? That obviously requires a lot more knowledge and
engineering judgement.
. . .
Well, Ian, the BLE paper reports data allowing one to make that engineering
judgement. It's unfortunate that my copy of the paper is in my library in
Florida, and I won't be back there until November to scan it for the group.
However, I have ordered a copy from the Michigan State U library.

The BLE experiments were conducted to determine what combination of radials
would form the best simulation of a perfect ground, i.e., what combination
would achieve a field strength closest to the ideal calculated value. One
factor they considered is that when the spacing between adjacent wires in a
grid structure is 1/20 lambda or less, the effect is that of a continuous
reflecting surface. The spacing between radials is not exactly the same as a
grid structure, but the effect is similar.

BLE found that the optimum length of the radials in the ground is not related
to resonant length as it is with elevated radials. They found that the
principal reason for the optimum length concerns the volume containing the
significant energy in the electromagnetic fields in the space surrounding the
radiator that intersects the ground. They found that at a distance of 0.4
lambda from the radiator the energy in the fields has reduced to the level of
diminishing returns, where collecting the currents at a greater distance would
yield no significant decrease in loss resistance, and therefore no further
increase in field strength. Indeed, the field strength obtained with at least
90 radials 0.4 lambda in length was found to be insignificantly less than that
of a perfect ground. This fact was unknown prior to BLE's experiments. I can't
remember the exact difference shown in the graph, but it is inconsequential.

With the radials simulating a near-perfect reflecting ground plane the skin
depth of the earth beneath the radials is of no consequence, because the RF
energy is nearly totally reflected, with only an insignificant amount
transmitted through the ground plane. Consequently, the soil conditions
directly beneath the ground plane are irrevelant.

However, the soil conditions immediately external to the ground plane are
important to the intensity of the ground wave propagation from vertical
radiators. The poorer the soil conductivity the greater the loss at low angles
of elevation. And as we all know, propagation of the ground wave is frequency
sensitive. Many years ago, using the FCC propagation charts of field strength
vs distance for a conductivity of 8, the geographical area covered with a
field strenght of 1 mv/meter at 1 mile for a 250 watt station at 550 KHz would
require 47 kilowatts at 1500 KHz to cover the same area with the same signal
level.

When I receive the requested copy of the BLE paper I'll scan it and publish it
for all to see.

Walt, W2DU

In my previous post above I forgot to mention that the displacement currents
that enter the ground between the radials don't follow the lossy ground to the
center of the radial system. Instead, they quickly diffract to the nearest
radial and thus continue toward the center along the radial wire. Consequently,
the more radials the shorter distance the diffracted current has to travel to
reach the higher conductivity of the wire. The last I knew the FCC requires only
90 radials (every 4°) to comply with the regulations, but many BC antenna
engineers use 120 (every 3°).

I discussed this issue in Chapter 5 in both the 1st and 2nd editions of
Reflections, with a diagram of the diffraction phenomenon in Fig. 1.

Walt, W2DU

On Tue, 21 Jun 2005 17:35:11 -0400, "Walter Maxwell"
wrote:


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

Hi All,

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.

I'd like to hear your comments.

Hi Walt,

Thanx big time for this work of dedication. I have other projects to
attend to, but I am sure looking forward to close examination of this
trove of data by hunkering down with Mathcad and casting up some
charts. Hope to do that within the week if not sooner.

73's
Richard Clark, KB7QHC

Hi Richard,

Your mentioning Mathcad, (I have 2000i ed.) made me think of using Excel to
produce some graphs of the data, however, there are two other projects that must
come first. I have used Mathcad only to solve problems using the equations one
can build there, and have not explored the graphing possibilities. With both
Excel and Mathcad available do you think I should spend the time learning
graphics with Mathcad, or stick with Excel which I already know how to use?

Walt

Walt, I'm not Richard but my two cents would be stick with Excel. I
have a (now old) version of Mathcad (6.0) and don't use it much. It
is much better in handling complex numbers than Excel is tho.

Excel does the math just fine, but the clunky text results are a pain.

Also, I cannot recommend too highly Dan's (AC6LA) Excel based
programs. His MultiNEC front end for NEC, EZNEC, 4nec2, Antenna
Model, etc. is used all of the time here. For transmission line
stuff, including "building" matching networks XLZIZL is also
constantly in use at this QTH. Likewise his stand alone TLDetails.exe
should be in every ham's tool kit. (I'm a beginning amateur woodworker
and just like woodworkers, hams can never have too many tools.)

Walter Maxwell wrote:
. . .

When I receive the requested copy of the BLE paper I'll scan it and publish it
for all to see.

Is the publishing of copyrighted papers on the Web generally permitted
under fair use rules? The IEEE and other publishers of professional
papers charge around $25 for downloaded reprints, and I'd think that
would cut into their income. Or does the IEEE specifically permit
publishing of their papers on the Web?

Roy Lewallen, W7EL

Walter Maxwell wrote:

In my previous post above I forgot to mention that the displacement currents
that enter the ground between the radials don't follow the lossy ground to the
center of the radial system. Instead, they quickly diffract to the nearest
radial and thus continue toward the center along the radial wire. Consequently,
the more radials the shorter distance the diffracted current has to travel to
reach the higher conductivity of the wire. The last I knew the FCC requires only
90 radials (every 4°) to comply with the regulations, but many BC antenna
engineers use 120 (every 3°).

I discussed this issue in Chapter 5 in both the 1st and 2nd editions of
Reflections, with a diagram of the diffraction phenomenon in Fig. 1.

This interaction among radials has quite a dramatic effect on the
effective ground conductivity. I noticed and reported quite some time
ago that Reg's ground radial program produced answers which disagree
strongly with both BLE and NEC-4 modeling (which agree with each other
reasonably well), and speculated that he didn't account for this
interaction in his program. (I haven't checked since to see if the
program has been modified.) All he says about having to trust the writer
of the program if you don't have access to the source code is true.

Roy Lewallen, W7EL

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.

On Wed, 22 Jun 2005 08:57:00 -0700, Roy Lewallen
wrote:

Walter Maxwell wrote:
. . .

When I receive the requested copy of the BLE paper I'll scan it and publish it
for all to see.

Is the publishing of copyrighted papers on the Web generally permitted
under fair use rules? The IEEE and other publishers of professional
papers charge around $25 for downloaded reprints, and I'd think that
would cut into their income. Or does the IEEE specifically permit
publishing of their papers on the Web?

Unless I'm mistaken, the copyright would have had to been renewed to
remain in effect.

According to this link:

http://www.scils.rutgers.edu/~lesk/copyrenew.html

it was not.

On Wed, 22 Jun 2005 09:33:33 -0700, Wes Stewart
wrote:

According to this link:

http://www.scils.rutgers.edu/~lesk/copyrenew.html

it was not.

Hi Wes,

You should take care to observe the proviso offered:
"This file does not contain listings for music, movies, or
periodicals."

The practice of many journals is that your material, offered for
publication, is accepted only with the explicit rights of ownership
being transferred to that society. In fact, if you were to cite your
own work without giving a reference to that society's publication,
then you could be held accountable for plagiarism.

The "Open Source" movement has sparked a debate in this regard and
academic authors are being better versed on methods that allow them to
both publish and retain rights.

73's
Richard Clark, KB7QHC

Wes Stewart wrote:

Unless I'm mistaken, the copyright would have had to been renewed to
remain in effect.

According to this link:

http://www.scils.rutgers.edu/~lesk/copyrenew.html

it was not.

Thanks for the URL - it looks like it'll come in handy. Unfortunately,
the fourth sentence on that page is "This file does not contain listings
for music, movies, or periodicals." The BLE paper was published in the
_Proceedings of the IRE_, a periodical.

Roy Lewallen, W7EL

"Roy Lewallen" wrote in message
...
Walter Maxwell wrote:
. . .

When I receive the requested copy of the BLE paper I'll scan it and publish
it for all to see.

Is the publishing of copyrighted papers on the Web generally permitted under
fair use rules? The IEEE and other publishers of professional papers charge
around $25 for downloaded reprints, and I'd think that would cut into their
income. Or does the IEEE specifically permit publishing of their papers on the
Web?

Roy Lewallen, W7EL

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

Walt

On Wed, 22 Jun 2005 13:49:11 -0400, "Walter Maxwell"
wrote:

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

Hi Walt,

You cannot imagine how difficult it is to track down rights' holders.
The presumption does not lie in copyright having expired
automatically. Many organizations hire lawyers for no other purpose
than this paper chase. The author's name is becoming increasingly
irrelevant in this age of information.

73's
Richard Clark, KB7QHC