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