"Howard Kowall" wrote in
:

Hello All

....
I guess it has it place) I have decide to try something new and
hopefully better.Here it is, the Mystery Antenna,I had all the parts
....

Now, lets see... that the "multi-band wire antenna that performs
exceptionally well even though it confounds antenna modeling software".

Yet another 'magic' antenna who's 'magic' cannot be explained!

Of course the claim is nonsense, the antenna can be modelled in NEC...
just the complication is evaluating an equivalent load in NEC terms for
the TL stubs.

You can evaluate the equivalent impedance of a s/c stub of 16.5' of RG8X
(or whatever you used) using the calculator at
http://www.vk1od.net/tl/tllc.php.

For example Z of s/c stub of 16.5' of RG8X at 7.1MHz is around 2.97
+j64.54, so it acts like a quite lossy inductor at that frequency.

Once the feedpoint impedance is found, the transmission line losses and
ATU losses can be evaluated for a system perspective.

Ask yourself why they choose to not model the antenna. Often, when people
claim that an antenna can't be modelled in reality just don't like the
answers.

Owen

Owen Duffy wrote:

...
Ask yourself why they choose to not model the antenna. Often, when people
claim that an antenna can't be modelled in reality just don't like the
answers.

Owen

I think they did model it, and compared the results against actual
hands-on observations, readings, contacts, etc.

This is why they make the claim NEC is missing something ... they simply
believe their eyes, ears and meter readings and signal reports ...

Regards,
JS

John Smith wrote:
Owen Duffy wrote:

...
Ask yourself why they choose to not model the antenna. Often, when
people claim that an antenna can't be modelled in reality just don't
like the answers.

Owen

I think they did model it, and compared the results against actual
hands-on observations, readings, contacts, etc.

This is why they make the claim NEC is missing something ... they simply
believe their eyes, ears and meter readings and signal reports ...

Let's not forget the possibility that they didn't know how to model the
thing. I'm no great shakes at modeling, and that antenna is beyond my
prowess at the present.

Of course, I'm mpore likely to assume that discrepancies between
computer world and reality are my fault. Some others might assume that
the data they input was correct, so it must be the programs fault....

And some on the fringe might say the antenna CAN't work - the computer
says it can't!

- 73 de Mike N3LI -

Michael Coslo wrote:


Let's not forget the possibility that they didn't know how to model the
thing. I'm no great shakes at modeling, and that antenna is beyond my
prowess at the present.

Of course, I'm mpore likely to assume that discrepancies between
computer world and reality are my fault. Some others might assume that
the data they input was correct, so it must be the programs fault....

And some on the fringe might say the antenna CAN't work - the computer
says it can't!

- 73 de Mike N3LI -

Absolutely, I am NOT making any statement "they" are correct (I have
never tried this antenna myself--either as a model or as an actual
antenna in reality.)

But, anyway you cut it, and on the ground floor, there ARE discrepancies
in the basic equations, formulas and assumptions being put to use in the
NEC, someday these will be fleshed out ...

Regards,
JS

John Smith wrote:
Michael Coslo wrote:


Let's not forget the possibility that they didn't know how to model
the thing. I'm no great shakes at modeling, and that antenna is beyond
my prowess at the present.

Of course, I'm mpore likely to assume that discrepancies between
computer world and reality are my fault. Some others might assume that
the data they input was correct, so it must be the programs fault....

And some on the fringe might say the antenna CAN't work - the computer
says it can't!

- 73 de Mike N3LI -

Absolutely, I am NOT making any statement "they" are correct (I have
never tried this antenna myself--either as a model or as an actual
antenna in reality.)

But, anyway you cut it, and on the ground floor, there ARE discrepancies
in the basic equations, formulas and assumptions being put to use in the
NEC, someday these will be fleshed out ...

Regards,
JS

I doubt that any antenna an amateur is likely to build has some physics
not adequately modeled by the math in NEC. Exactly what might be these
discrepancies in equations, formulae and assumptions? Considering that
NEC has had decades of validation against actual measurements and a lot
of really, really smart people looking at how it works, I'd be kind of
surprised.

However, I can also easily believe that an amateur (or professional)
could build an antenna that has measured performance different than
expected from their NEC model of that antenna. The differences would
lie, most likely, in these areas:
1) Inaccuracies in the model itself. Things like earth properties (NEC
assumes uniform dielectric, it isn't) are an important source of error
for antennas close to the ground. Most amateur models do not include a
very good model of the surroundings (supports, trees, feedlines, etc.)

2) Inaccuracies in the measurements or not measuring the right things. A
good example is using NEC to get feedpoint characteristics, then
measuring at the rig, and not properly accounting for the transmission
line, particularly if the feedpoint Z is reactive.

In the professional antenna world, if someone models an antenna, then
builds it and tests it on the range, and the measurements differ from
what the model predicted, the usual assumption is that what was built
differed from what was modeled, or the measurements were off.

Jim Lux wrote:
John Smith wrote:
[A bunch of chit Jim, obviously, will/and does differ with]
Regards,
JS



I doubt that any antenna an amateur is likely to build has some physics
not adequately modeled by the math in NEC. Exactly what might be these
discrepancies in equations, formulae and assumptions? Considering that
NEC has had decades of validation against actual measurements and a lot
of really, really smart people looking at how it works, I'd be kind of
surprised.

I don't believe the above it correct. Indeed, if you will only review
my past objections and reflections on how "the NEC engine" demonstrates
"differences" you will be focused at the "focal point" of my "inquiries" ...


However, I can also easily believe that an amateur (or professional)
could build an antenna that has measured performance different than
expected from their NEC model of that antenna. The differences would
lie, most likely, in these areas:

Look, the dipole, standard monopole (1/4, 1/2, longwire, etc.) is NOT in
debate. Indeed, it is like NEC was designed to "explain/model" these, DUH!

1) Inaccuracies in the model itself. Things like earth properties (NEC
assumes uniform dielectric, it isn't) are an important source of error
for antennas close to the ground. Most amateur models do not include a
very good model of the surroundings (supports, trees, feedlines, etc.)

2) Inaccuracies in the measurements or not measuring the right things. A
good example is using NEC to get feedpoint characteristics, then
measuring at the rig, and not properly accounting for the transmission
line, particularly if the feedpoint Z is reactive.

In the professional antenna world, if someone models an antenna, then
builds it and tests it on the range, and the measurements differ from
what the model predicted, the usual assumption is that what was built
differed from what was modeled, or the measurements were off.

I could pick apart the above, attempt to poke fun, etc. -- however, I
would much rather join forces and attempt to focus on the points which
would lead us to real answers -- i.e., the arrl and illiterates have
already done enough damage, let us pursue a more productive path?

Leave us leave our minds open, OK?

Regards,
JS

John Smith wrote:

...
Leave us leave our minds open, OK?

Regards,
JS


And damn, and DAMN, and well DAMN ...

If you want to build something from a 19?? to 1950 (or beyond?)
publications, do I stop you? Is this what "you have you back up your
ego about?" It this what threatens you? If so, go ahead, go to your
grave with your pursuits, without my critique! ...

I am here about what "I AM", about "WHAT I THINK", about "WHAT I SEE",
about "WHAT I SUSPECT", about "WHAT I WONDER", about "MY QUESTIONS TO
OTHER MEN/WOMEN", about what I simply want to think about and want
answers to ... yanno, I think you are really endangerd by those "others"
here, I find ... Cecil, where are you? evil grin

If you can't participate, if you think I am am an idiot, if you think I
am a moron ... could you do it politely until I give you reason to do
differently ... indeed, I may feel threaten my "moronic brains" and
respond ... please don't take insult, just reassure me I am not wrong ...

Regards,
JS

John Smith wrote:
I don't believe the above is correct.

Proof that NEC cannot model everything is at:

http://www.w5dxp.com/SUPRGAIN.EZ

Would you believe a vertical with
24 dBi omnidirectional gain?
--
73, Cecil http://www.w5dxp.com
"According to the general theory of relativity,
space without ether is unthinkable." Albert Einstein

Jim Lux wrote:

I doubt that any antenna an amateur is likely to build has some physics
not adequately modeled by the math in NEC. Exactly what might be these
discrepancies in equations, formulae and assumptions? Considering that
NEC has had decades of validation against actual measurements and a lot
of really, really smart people looking at how it works, I'd be kind of
surprised.

However, I can also easily believe that an amateur (or professional)
could build an antenna that has measured performance different than
expected from their NEC model of that antenna. The differences would
lie, most likely, in these areas:
1) Inaccuracies in the model itself. Things like earth properties (NEC
assumes uniform dielectric, it isn't) are an important source of error
for antennas close to the ground. Most amateur models do not include a
very good model of the surroundings (supports, trees, feedlines, etc.)

2) Inaccuracies in the measurements or not measuring the right things. A
good example is using NEC to get feedpoint characteristics, then
measuring at the rig, and not properly accounting for the transmission
line, particularly if the feedpoint Z is reactive.

In the professional antenna world, if someone models an antenna, then
builds it and tests it on the range, and the measurements differ from
what the model predicted, the usual assumption is that what was built
differed from what was modeled, or the measurements were off.

A lot of people are aware that some knowledge and skill is necessary in
order to construct a good model which will give accurate results. What's
not so widely appreciated is how difficult it is to make decent
measurements of even such seemingly simple things as impedance, let
alone gain and pattern.

Some years ago I was at what was then NOSC (Naval Ocean Systems Center)
in San Diego, where they had the very best equipment to do full 3D
pattern measurements of antennas mounted on carefully constructed and
accurate scale models of U.S. Navy ships. They were also modeling the
antennas and ship structures with NEC-4. One of the engineers confided
to me that they'd learned that when the measurement disagreed with the
model result, the model result was probably better. Of course, these
people were very highly skilled in using the modeling software and how
to avoid and detect its limitations. But they were also very highly
skilled in making the best possible measurements.

A claim by an antenna manufacturer or creator that an antenna "can't be
modeled by NEC" very often means that NEC's accurate results don't back
up the manufacturer's or creator's inflated claims. If the claim
includes a statement that some alleged physical rule or phenomenon
("critical coupling" comes to mind) isn't "accounted for" by NEC, you
can be certain that the disparity is due to inflated claims rather than
a shortcoming of NEC. There are, of course, some antennas that truly
can't be modeled with NEC, for example a patch antenna with dielectric
between the patch and ground plane. But those of NEC's limitations that
aren't apparent from the basic program structure have been pretty well
discovered and documented in the 30 years or so it's been in use.

Antennas are being designed every day with NEC and EZNEC which provide
critical communications functions for military and government agencies,
aerospace companies, space agencies, domestic and international
broadcasters, scientific researchers, and many others. Many of those
antennas have been carefully measured and verified before being put into
service, and countless of them are in current use. I personally have
designed a number of antennas with EZNEC, tested physical prototypes at
a professional range, and seen them put into daily service performing
critical functions as designed.

Roy Lewallen, W7EL

Roy Lewallen wrote:
Jim Lux wrote:

I doubt that any antenna an amateur is likely to build has some
physics not adequately modeled by the math in NEC. Exactly what might
be these discrepancies in equations, formulae and assumptions?
Considering that NEC has had decades of validation against actual
measurements and a lot of really, really smart people looking at how
it works, I'd be kind of surprised.

However, I can also easily believe that an amateur (or professional)
could build an antenna that has measured performance different than
expected from their NEC model of that antenna. The differences would
lie, most likely, in these areas:
1) Inaccuracies in the model itself. Things like earth properties (NEC
assumes uniform dielectric, it isn't) are an important source of error
for antennas close to the ground. Most amateur models do not include a
very good model of the surroundings (supports, trees, feedlines, etc.)

2) Inaccuracies in the measurements or not measuring the right things.
A good example is using NEC to get feedpoint characteristics, then
measuring at the rig, and not properly accounting for the transmission
line, particularly if the feedpoint Z is reactive.

In the professional antenna world, if someone models an antenna, then
builds it and tests it on the range, and the measurements differ from
what the model predicted, the usual assumption is that what was built
differed from what was modeled, or the measurements were off.

A lot of people are aware that some knowledge and skill is necessary in
order to construct a good model which will give accurate results. What's
not so widely appreciated is how difficult it is to make decent
measurements of even such seemingly simple things as impedance, let
alone gain and pattern.

Some years ago I was at what was then NOSC (Naval Ocean Systems Center)
in San Diego, where they had the very best equipment to do full 3D
pattern measurements of antennas mounted on carefully constructed and
accurate scale models of U.S. Navy ships. They were also modeling the
antennas and ship structures with NEC-4. One of the engineers confided
to me that they'd learned that when the measurement disagreed with the
model result, the model result was probably better. Of course, these
people were very highly skilled in using the modeling software and how
to avoid and detect its limitations. But they were also very highly
skilled in making the best possible measurements.

A claim by an antenna manufacturer or creator that an antenna "can't be
modeled by NEC" very often means that NEC's accurate results don't back
up the manufacturer's or creator's inflated claims. If the claim
includes a statement that some alleged physical rule or phenomenon
("critical coupling" comes to mind) isn't "accounted for" by NEC, you
can be certain that the disparity is due to inflated claims rather than
a shortcoming of NEC. There are, of course, some antennas that truly
can't be modeled with NEC, for example a patch antenna with dielectric
between the patch and ground plane. But those of NEC's limitations that
aren't apparent from the basic program structure have been pretty well
discovered and documented in the 30 years or so it's been in use.

Antennas are being designed every day with NEC and EZNEC which provide
critical communications functions for military and government agencies,
aerospace companies, space agencies, domestic and international
broadcasters, scientific researchers, and many others. Many of those
antennas have been carefully measured and verified before being put into
service, and countless of them are in current use. I personally have
designed a number of antennas with EZNEC, tested physical prototypes at
a professional range, and seen them put into daily service performing
critical functions as designed.

Roy Lewallen, W7EL


Oh, I C ... You will excuse me then, I have had a bit too much to drink,
to be coherent ... but then, from your response, you are in the same
shape, right? :-)

Regards,
JS