Cecil Moore, W5DXP wrote:
"For instance, a coil might be 10+j300 ohms or a cap might be 2-j500
ohms."

A small loop antenna with a perimeter only a small fraction of a
wavelength has almost uniform current throughout. Its impedance is an
inductive reactance in series with a resistance. The U.S. Bureau of
Standards published inductance formulas for single-turn and several-turn
loops in Bulletin 74. Results can`t take into account loss from
radiation so they are approximate.

Arnold King gives an approximate formula for the radiation resistance of
a small one-turn loop in "Transmission Lines, Antennas, and Wave
Guides":
Re = 20(Beta)to the 4th power times A squared
Beta=2pi/lambda
A=area enclosed by the loop.

Best regards, Richard Harrison, KB5WZI

Cecil Moore wrote:

Or maybe not. EZNEC apparently won't properly model
the Lattin antenna. www.g3ycc.karoo.net/lattin.htm
. . .

I took a look at it, and sure enough, it can't. The antenna is
constructed from tubular 300 ohm twinlead, and EZNEC has no way to
account for the dielectric between conductors. In that antenna, it looks
like the velocity factor of the differential mode field between
conductors would be important to its operation, and without the ability
to model the dielectric between conductors, EZNEC wouldn't get the
velocity factor right.

When I see a claim that EZNEC can't model a particular antenna, I often
find that the reason for the claim is that the antenna's inventor or
seller has dreamed up some magical property to explain the impossibly
good performance he's claiming for the antenna. EZNEC models the antenna
just fine, it just doesn't model the magical property and validate the
claims -- that is, it shows how the antenna really works, not how the
huckster claims it works. But there are, certainly, some kinds of
antennas which it really can't model properly for one reason or another.
The Lattin antenna is one of those.

Roy Lewallen, W7EL

On Thu, 07 Apr 2005 10:05:04 -0700, Roy Lewallen
wrote:

But there are, certainly, some kinds of
antennas which it really can't model properly for one reason or another.
The Lattin antenna is one of those.

Hi Roy,

Having model dozens of variations of this antenna, as well as what was
described in the patent - I cannot think of one reason why it should
work except through haphazard luck. Certainly the offered "theories"
are no more credible than those for other antennas that defy modeling
such as the single or double bazooka, the eh, the cfa.

This antenna has many reports of its confounding expectation and then
in the same breath those who are confounded expressing their sincere
belief it works. It's one of those situations where the builder can't
get it to sing, but has a brother-in-law who knows this fellow who
lives next door to one who can, but who took it down ten years ago
because it was so hard to tune.

Perhaps you could widen your customer base if you added a "belief
scale" to the available control settings for EZNEC. It could range
from "agnostic" to "I believe in miracles."

73's
Richard Clark, KB7QHC

John Smith wrote:

Cecil:

Take a look at this folded wave monopole...
I am playing with a reflector and director to sandwich this driven element
between....
This is the design I have in mind, NO groundplane radials when used as a
stand-alone vertical monopole/end-fed.

There are warnings in EZNEC about segments not lining up
between close spaced wires. My 29 dBi omnidirectional
antenna is an example of what happens when one ignores
the segment alignment between closely spaced segments.

I have modified your segmentation to try to follow the
EZNEC guidelines and that file is attached. There is
quite a change in the results. The feedpoint impedance
went from 2.787+j15.47 to 0.7587+j22.69, the gain went
from 7.23 dBi to 3.16 dBi, and the TOA went from 6 deg
to 9 deg. I standardized on one foot per segment.

I don't really understand what you are trying to do and
am just the messenger.
--
73, Cecil http://www.qsl.net/w5dxp

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Cecil:

Did you remember to attach the file? I don't see it, but would love to
study your changes...
At ~2.7 ohms I can use a 1:16 balun (reversed direction from conventional
use) to mate the antenna with 50 ohms, and get an acceptable SWR...
Cecil, try to hear this in a positive manner: If I must conform to EZNEC,
then any creativity must be abandoned... If I conform to all the rules of
the past and the "Absolute Truths" encompassed by any application--how could
I ever hope for a new discovery of geometry or configuration, or the
possible use of un-used manipulations of existing rules?
If one travels the same road, takes the same plane, rides the same rail,
boards the same boat, walks the same path--he sees only the same sights,
that which is common place.... even futile paths invoke my curriosity--as
just a change of scenery can be enjoyed many times.
If that argument is carried out to its nth degree, only one question would
remain, "Why should I bother with any of this?", it would be quite easy for
a programmer to create a program which quizzes you on ant type (monopole,
dipole, yagi, 1/2 wave, 1/4 wave, center loaded, bottom loaded, etc, etc),
the freq etc... then constructs the antenna for you. Including suggesting
height, mounting brackets and a host of other varibles and conditions that
tasks the mind to consider... In other words, once I give control and
authority to EZNEC, why should it not "do it all?"
But then, even if it did, I would still dilly around with these copper,
aluminum and stainless bits and pieces. grin
You have talked me back into abandoning EZNEC....

Regards,
John

--
I would like to point out, I do appreciate the "Been there--done that!"
posts. Indeed, now your observations, comments and discourse should be
filled with wisdom--I am listening!!!
"Cecil Moore" wrote in message
...
John Smith wrote:

Cecil:

Take a look at this folded wave monopole...
I am playing with a reflector and director to sandwich this driven
element
between....
This is the design I have in mind, NO groundplane radials when used as a
stand-alone vertical monopole/end-fed.

There are warnings in EZNEC about segments not lining up
between close spaced wires. My 29 dBi omnidirectional
antenna is an example of what happens when one ignores
the segment alignment between closely spaced segments.

I have modified your segmentation to try to follow the
EZNEC guidelines and that file is attached. There is
quite a change in the results. The feedpoint impedance
went from 2.787+j15.47 to 0.7587+j22.69, the gain went
from 7.23 dBi to 3.16 dBi, and the TOA went from 6 deg
to 9 deg. I standardized on one foot per segment.

I don't really understand what you are trying to do and
am just the messenger.
--
73, Cecil http://www.qsl.net/w5dxp

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet
News==----
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Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption
=----

Richard H:

Do you happen to have a URL handy where I could view "Bulletin 74?"

Thanks in advance,
warmest regards,
John

--
I would like to point out, I do appreciate the "Been there--done that!"
posts. Indeed, now your observations, comments and discourse should be
filled with wisdom--I am listening!!!
"Richard Harrison" wrote in message
...
Cecil Moore, W5DXP wrote:
"For instance, a coil might be 10+j300 ohms or a cap might be 2-j500
ohms."

A small loop antenna with a perimeter only a small fraction of a
wavelength has almost uniform current throughout. Its impedance is an
inductive reactance in series with a resistance. The U.S. Bureau of
Standards published inductance formulas for single-turn and several-turn
loops in Bulletin 74. Results can`t take into account loss from
radiation so they are approximate.

Arnold King gives an approximate formula for the radiation resistance of
a small one-turn loop in "Transmission Lines, Antennas, and Wave
Guides":
Re = 20(Beta)to the 4th power times A squared
Beta=2pi/lambda
A=area enclosed by the loop.

Best regards, Richard Harrison, KB5WZI

John Smith wrote:
"Do you happen to have a URL handy where I could view "Bulletin 74?"

I searched the web unsuccessfully, including some NIST sites which
dictated schedules for clearing their files at certain file ages. But, I
did find a reference to the famous bulletin in Keith Henney`s 1950
edition of "Radio Engineering Handbook". On page 132, Keith writes:
"It is possible to calculate the true (l-f) inductance of some types of
air-cored coils with a fair degree of accuracy. National Bureau of
Standards Circular 74 has long been the most authorative source of such
information. Some of the most useful contained therein are reproduced
here."

Pages of information follow which include design charts which I can`t
reproduce due to my limitations. Such information is not copyrighted as
it is assumed the taxpayer has paid for collection of the information
already, and should not have to pay for it a second time. That was pre
Bush policy, of course.

You can probably borrow a copy of Keith Henney`s book in a library near
you and delight ijn designing your own antenna coil. The publisher was
McGraw-Hill.

Best regards, Richard Harrison, KB5WZI

On Sat, 9 Apr 2005 23:39:15 -0500, (Richard
Harrison) wrote:

National Bureau of
Standards Circular 74 has long been the most authorative source of such
information. Some of the most useful contained therein are reproduced
here."

Hi Richard,

Some background material:
"George Southworth was born in Little Cooley, Pennsylvania, in
1890 and became interested in radio while still in high school. He
graduated with a degree in physics from Grove City College in 1914
and then studied for a year at Columbia University. In June 1917
he joined the Radio Section of the U.S. National Bureau of
Standards and assisted in the preparation of the influential
Bulletin 74 entitled Radio Instruments and Measurements, published
in1918.
... [some time later]
"In 1931 he began a study of wave propagation in dielectric rods,
although the project did not yet have official authorization. By
early 1932, he observed wave propagation in a water-filled copper
pipe. Theoretical analysis related to Southworth's experiments was
carried out by John R. Carson, Sergei A. Schelkunoff, and Sallie
P. Mead during 1932.
"Using high-frequency vacuum tubes imported from France,
Southworth transmitted waves through air-filled copper pipes up to
20 feet long by May 1933. He later recalled that the first message
sent through a waveguide was 'Send money.'"

73's
Richard Clark, KB7QHC

On Sat, 9 Apr 2005 23:39:15 -0500, (Richard
Harrison) wrote:

I searched the web unsuccessfully
http://www.hills2.u-net.com/private/...4/CONTENTS.HTM
contains partial page transcriptions.

Employing the search term "Radio Instruments and Measurements" at:
http://www.kartoo.com/
you can make use of an unique, cluster based search engine that
represents the next wave of sifting information on the Web.

You will find references to this tome (hardly a circular or bulletin)
of more than 600 pages (you will also find book venders ready to sell
this work for $20-$30). One NIST site contains a quote from Edison:
" . . . This is the greatest book on this subject that I have ever
read, and I want to congratulate you and your Bureau on its
production."

There are multiple authors. I cited one, George Clark Southworth,
another was J. Howard Dellinger.

There are hard copies available through NIST's Historical Archives
(try to get one though).

73's
Richard Clark, KB7QHC

Richard:

Could these be them; or, are these not the same?

http://www.fcc.gov/mb/audio/decdoc/r...bulletins.html

Regards
--
I would like to point out, I do appreciate the "Been there--done that!"
posts. Indeed, now your observations, comments and discourse should be
filled with wisdom--I am listening!!!
"Richard Clark" wrote in message
...
On Sat, 9 Apr 2005 23:39:15 -0500, (Richard
Harrison) wrote:

I searched the web unsuccessfully
http://www.hills2.u-net.com/private/...4/CONTENTS.HTM
contains partial page transcriptions.

Employing the search term "Radio Instruments and Measurements" at:
http://www.kartoo.com/
you can make use of an unique, cluster based search engine that
represents the next wave of sifting information on the Web.

You will find references to this tome (hardly a circular or bulletin)
of more than 600 pages (you will also find book venders ready to sell
this work for $20-$30). One NIST site contains a quote from Edison:
" . . . This is the greatest book on this subject that I have ever
read, and I want to congratulate you and your Bureau on its
production."

There are multiple authors. I cited one, George Clark Southworth,
another was J. Howard Dellinger.

There are hard copies available through NIST's Historical Archives
(try to get one though).

73's
Richard Clark, KB7QHC