On 19 Apr 2004 05:14:44 -0700, (N2EY) wrote:

Why a stub that is excited
along its length should behave as a trap is not explained, nor how the
shortened sections act as loading coils (the entire antenna is only
112' 4" long, plus connections).

Hi Jim,

Simply because the so-called explanations are more wish than reality.
I've not slackened my study of this design. I've done thirty or forty
measurements that have interest in their own right, but show the
"theory" is sheer fantasy. These notions of tuned stubs as traps are
so far off the mark in practice that no one notices they don't make
sense electrically either.


Modeling the thing looks like a real challenge for a whole bunch of
reasons. The gaps between sections may be important, for example.

....

I suspect that a key element to the antenna's operation is the use of
the tubular Twin-Lead, with its 0.8 velocity factor. This stuff is
probably close to being unobtanium these days. Another point is the
extreme narrowness of resonance on most bands.

These apologies ring false. The issue of gaps is desperate and the
selection of tubular has no basis in special characteristics. All
such considerations MUST yield to simple scaling. For instance, if
you need 0.8 and have 0.9, there is no magic formula beyond
proportions necessary to achieve "what should be."

The difficulty lies in the supposed explanations.

The W5GI antenna seems to be a variation on the Lattin theme.

And it is even more gauche. It approaches antenna design as an allied
art of Palmistry.

73's
Richard Clark, KB7QHC

Richard Clark wrote in message . ..
On 19 Apr 2004 05:14:44 -0700, (N2EY) wrote:

Why a stub that is excited
along its length should behave as a trap is not explained, nor how the
shortened sections act as loading coils (the entire antenna is only
112' 4" long, plus connections).

Hi Jim,

Simply because the so-called explanations are more wish than reality.
I've not slackened my study of this design. I've done thirty or forty
measurements that have interest in their own right, but show the
"theory" is sheer fantasy. These notions of tuned stubs as traps are
so far off the mark in practice that no one notices they don't make
sense electrically either.
Modeling the thing looks like a real challenge for a whole bunch of
reasons. The gaps between sections may be important, for example.

...

I suspect that a key element to the antenna's operation is the use of
the tubular Twin-Lead, with its 0.8 velocity factor. This stuff is
probably close to being unobtanium these days. Another point is the
extreme narrowness of resonance on most bands.

These apologies ring false. The issue of gaps is desperate and the
selection of tubular has no basis in special characteristics. All
such considerations MUST yield to simple scaling. For instance, if
you need 0.8 and have 0.9, there is no magic formula beyond
proportions necessary to achieve "what should be."

I disagree! In the QST article, Lattin describes an 80/40 dipole using
his method. It has wires dangling from the stub junctions to get 40
meter resonance.

The difficulty lies in the supposed explanations.

Agreed. They are oversimplified at best and just plain wrong at worst.
However, I take it as a given that W4JRW got the results he claimed
from the antennas he built.

The fact that people report so much trouble duplicating and modeling
the W4JRW antennas indicates to me that there is more to it than meets
the eye - and maybe more than met W4JRW's eye, as well.

Most important to me is that the antenna offers no real advantages
over, say, a conventional trap dipole. Yet it offers many
disadvantages, such as mechanical frailty and difficulty of
duplication.


The W5GI antenna seems to be a variation on the Lattin theme.

And it is even more gauche. It approaches antenna design as an allied
art of Palmistry.

HAW!

And again - what advantages does it have over, say, a W3DZZ trap
dipole?

73 de Jim, N2EY

On 20 Apr 2004 09:06:35 -0700, (N2EY) wrote:
These apologies ring false. The issue of gaps is desperate and the
selection of tubular has no basis in special characteristics. All
such considerations MUST yield to simple scaling. For instance, if
you need 0.8 and have 0.9, there is no magic formula beyond
proportions necessary to achieve "what should be."

I disagree! In the QST article, Lattin describes an 80/40 dipole using
his method. It has wires dangling from the stub junctions to get 40
meter resonance.

Hi Jim,

OK, you disagree, but with what? Scaling will ALWAYS answer
everything but the mystical apologies.


Most important to me is that the antenna offers no real advantages
over, say, a conventional trap dipole. Yet it offers many
disadvantages, such as mechanical frailty and difficulty of
duplication.

This is more pilot error than design error (which has its own
problems, of course).

And again - what advantages does it have over, say, a W3DZZ trap
dipole?

I see no such issues if the theory were hammered out. It is plainly
these readings of tea leaves that frustrate construction, because when
a design is described, it is most clear and concise - it just doesn't
work is all.

Like I said, I've done some measures and added a dozen more since.
The results are interesting. I can come up with a four band antenna
without too much trouble; however, getting those bands into Ham
regions (all of them) is another matter. I can do this with a simple
run of twin lead, and one strategically placed short between them.

This antenna (usefully resonant or otherwise) is no worse than any
wire strung between poles - just two wires instead of one, hardly what
I would call fragile. If it has an advantage over your W3DZZ trap
dipole, I leave that strictly in the eye of the beholder as I have
full faith it won't be any worse.

Any way, such work offers a step towards an antenna with MORE gain
(and more wire, a third one) by constructing a Franklin Array style of
antenna. True, not a multi bander, but I am not particularly nailed
to the floor over that.

73's
Richard Clark, KB7QHC

Richard Clark wrote in message . ..
On 20 Apr 2004 09:06:35 -0700, (N2EY) wrote:
These apologies ring false. The issue of gaps is desperate and the
selection of tubular has no basis in special characteristics. All
such considerations MUST yield to simple scaling. For instance, if
you need 0.8 and have 0.9, there is no magic formula beyond
proportions necessary to achieve "what should be."

I disagree! In the QST article, Lattin describes an 80/40 dipole using
his method. It has wires dangling from the stub junctions to get 40
meter resonance.

Hi Jim,

OK, you disagree, but with what?

With the idea that scaling answers all questions.

Scaling will ALWAYS answer
everything but the mystical apologies.

The two-band 80/40 dipole in the QST article has extra wires at the
junctions of the 80 and 40 sections because (according to the author)
the velocity factor of the tubular Twin Lead makes it necessary. Those
wires might or might not be required with a unity velocity factor.

Most important to me is that the antenna offers no real advantages
over, say, a conventional trap dipole. Yet it offers many
disadvantages, such as mechanical frailty and difficulty of
duplication.

This is more pilot error than design error (which has its own
problems, of course).

In a perfect world, maybe. But in the real world of ham radio, most
hams have limited materials, test equipment, time and space. An
antenna made out of unobtainable materials, which requires
unobtainable tools and test equipment to build and adjust is only of
academic interest to a ham.

And again - what advantages does it have over, say, a W3DZZ trap
dipole?

I see no such issues if the theory were hammered out. It is plainly
these readings of tea leaves that frustrate construction, because when
a design is described, it is most clear and concise - it just doesn't
work is all.

Exactly! If it cannot be easily duplicated by a ham with typical
resources, what good is it?


Like I said, I've done some measures and added a dozen more since.
The results are interesting. I can come up with a four band antenna
without too much trouble; however, getting those bands into Ham
regions (all of them) is another matter. I can do this with a simple
run of twin lead, and one strategically placed short between them.

Which is not what Lattin did at all. Your design sounds far superior.
Is it on the web anywhere?

This antenna (usefully resonant or otherwise) is no worse than any
wire strung between poles - just two wires instead of one, hardly what
I would call fragile. If it has an advantage over your W3DZZ trap
dipole, I leave that strictly in the eye of the beholder as I have
full faith it won't be any worse.

All depends on the wires. I use recycled #12 house wire, which stands
up under ice loading and high winds here in EPA. Yet it is hardly
noticed by the neighbors.

Any way, such work offers a step towards an antenna with MORE gain
(and more wire, a third one) by constructing a Franklin Array style of
antenna. True, not a multi bander, but I am not particularly nailed
to the floor over that.

The main attraction of the Lattin is its claim to multiband operation.
Otherwise one might as well go with a plain dipole.

73 de Jim, N2EY

Scaling is a powerful analytical technique(*), but in some cases it can
be a little trickier than meets the eye.

Consider, for example, scaling a piece of TV twinlead to twice the
frequency so it'll behave exactly the same (both as a transmission line
and as a radiator) at the new frequency.

The wire diameters have to be reduced by a factor of two.
The spacing between the wires has to be reduced by a factor of two.

Luckily, if the scale model and the original are both in free space, then

The dielectric constant of the insulator remains unchanged.

And, almost always overlooked,

The wire conductivity has to be increased by a factor of two.
The dielectric conductivity has to be increased by a factor of two.

Fortunately, these last factors are usually unimportant. If the original
is made from copper, it isn't possible to scale to a much higher
frequency. But it's something to be kept in mind if loss is significant
and an accurate assessment of loss is necessary.

Permeability, incidentally, remains unchanged with frequency when scaling.

But even if you can neglect the conductivity scaling, you wouldn't be
able to run down to the store and buy a piece of the scaled twinlead to
use in your antenna for another band.

(*) Antennas are often scaled to higher frequencies for testing because
the scale model is a more convenient size. When I was involved in the
development of very high-speed sampling circuits, we often made scale
models of various structures (for example, coax connector to microstrip
transitions) at *lower* frequencies, so they'd be large enough to
measure and physically adjust.

Roy Lewallen, W7EL

On 22 Apr 2004 07:19:37 -0700, (N2EY) wrote:

Like I said, I've done some measures and added a dozen more since.
The results are interesting. I can come up with a four band antenna
without too much trouble; however, getting those bands into Ham
regions (all of them) is another matter. I can do this with a simple
run of twin lead, and one strategically placed short between them.

Which is not what Lattin did at all. Your design sounds far superior.
Is it on the web anywhere?

Hi Jim,

You should take care with my perverse generalizations, especially when
you follow it with:
The main attraction of the Lattin is its claim to multiband operation.
Otherwise one might as well go with a plain dipole.

A plain dipole is already mutibanded. This particular claim is easy
to achieve. It may not fall within interesting bands, but history
already suggests one dipole often serves more than one ham band if one
can accept the short comings (wrong directionality being key).

This is more a matter of the dichotomy of need: match and launch.
There may be more matching options than actual application of where it
is launched (too many lobes in the wrong directions).

In this sense, the trap serves to shorten the antenna to RESTRICT its
physical to electrical wavelength ratio to a quarter or less, thus
guaranteeing a mediocre performance from precious air space and
real-estate. If Art hadn't been nailed for a design 17dB below a
simple vertical, he would be here howling efficiency per unit length
(but, unfortunately in the wrong aspect - that's how you lose 17dB
behind the sofa).

Frankly, the Lattin has yet to prove to me that the notion of a
longitudinal stub as "trap" really holds any water. I've seen the
same "theory" applied to diametrically opposed designs. It is
pleasing to the arm-chair designer to mutter these ideas, but these
so-called streamers needed to make it work just yell foul on every
street corner. It is an ad-hoc design draped with academic mumblings
to lend it the appearance of legitimacy.

To extend my quote above, I have added yet another dozen measurements
to have nailed down patterns that emerged with the basis of a
consistent building paradigm (yeah, I know, gobbldygook). I seek to
generalize such claims as the Lattin makes and reduce them to a
practical minimum that are robust and repeatable. This is not to say
entirely useful, nor optimal.

I did the same thing with the fractal with 300 or more measurements
and reduced that junk science to a simple observation: you can push
more resonances into a length of wire, the more you kink it. Useful?
The test of time has shown that no one has made any money from those
same published 300 pages - why would I expect the Lattin to emerge
from 5 decades of neglect to eclipse that record? Frankly, the Lattin
simply confirms this simple observation, but is more controlled. It
may mature to a more repeatable design, but I doubt its inventor would
recognize it.

73's
Richard Clark, KB7QHC

Hi, all concerned:

Here's some anecdata (sic) ... :

OUAT, after reading something some where about the Lattin Labs antenna, I
put an 8-ft stub on the side of a 33-ft verticaloverlotsaradials.

I got a "new" indication of low-Z near 10M which wasn't there B4, to go
along with the 40M low-Z reading.

Received noise on 10M went up, from a well-defined nearby source, suggesting
that the el pattern might have come down some.

I moved the stub nearer the top, and found what I remember as a 3/4-wave
low-Z indication on 10M.

I think the KT-XX series of "diametrically opposed designs" use this method
of multibanding, as well.

Might even try this anecdata in Roy's Toy3, to see if its gui-ed
algorithm-ized academic mumblings prove this scandalous anecdata.

Shucks, if it can't be modeled, it can't be made to happen ;o)

Right?

73, Dave, N3HE




"Richard Clark" wrote in message
...
On 22 Apr 2004 07:19:37 -0700, (N2EY) wrote:

Like I said, I've done some measures and added a dozen more since.
The results are interesting. I can come up with a four band antenna
without too much trouble; however, getting those bands into Ham
regions (all of them) is another matter. I can do this with a simple
run of twin lead, and one strategically placed short between them.

Which is not what Lattin did at all. Your design sounds far superior.
Is it on the web anywhere?

Hi Jim,

You should take care with my perverse generalizations, especially when
you follow it with:

BIGSNIP


Frankly, the Lattin has yet to prove to me that the notion of a
longitudinal stub as "trap" really holds any water. I've seen the
same "theory" applied to diametrically opposed designs. It is
pleasing to the arm-chair designer to mutter these ideas, but these
so-called streamers needed to make it work just yell foul on every
street corner. It is an ad-hoc design draped with academic mumblings
to lend it the appearance of legitimacy.

To extend my quote above, I have added yet another dozen measurements
to have nailed down patterns that emerged with the basis of a
consistent building paradigm (yeah, I know, gobbldygook). I seek to
generalize such claims as the Lattin makes and reduce them to a
practical minimum that are robust and repeatable. This is not to say
entirely useful, nor optimal.

I did the same thing with the fractal with 300 or more measurements
and reduced that junk science to a simple observation: you can push
more resonances into a length of wire, the more you kink it. Useful?
The test of time has shown that no one has made any money from those
same published 300 pages - why would I expect the Lattin to emerge
from 5 decades of neglect to eclipse that record? Frankly, the Lattin
simply confirms this simple observation, but is more controlled. It
may mature to a more repeatable design, but I doubt its inventor would
recognize it.

73's
Richard Clark, KB7QHC

On Fri, 23 Apr 2004 06:19:29 -0400, "David J Windisch"
wrote:
Shucks, if it can't be modeled, it can't be made to happen ;o)

Right?

Hi Dave,

More the issue is if it can be made to happen, and it can't be modeled
- what happened? [After that we can then stare at our navels and ask
"what is IT?"]

73's
Richard Clark, KB7QHC