Linear decoupling traps
 

I am planning a two band antenna for 30 and 80m using linear traps.
The idea is to build the antenna of zip-cord type line 140ohm vf 0.73.
Trap is made using 1/4 wave shorted stub, decoupling occurs at the open end.
My question:
Is there any difference if the shorted end is pointing to the center or to
the tip of dipole.
Only the stub portion has two wires in parallell, the rest is only one wire.

----------------------------------------xxcenterxxx----
I_________

OR

----------------------------------------xxxxcenterxxx------
________I


73 Jouko OH5RM

Linear decoupling traps
 

On Apr 12, 11:54*am, "JN" wrote:
I am planning a two band antenna for 30 and 80m using linear traps.
73 Jouko OH5RM

Jouko.......you might try to GOOGLE:

"lattin antenna"

That may lead you to useful information.

Lee KA0FPJ

Linear decoupling traps
 

Jouko.......you might try to GOOGLE:

"lattin antenna"

That may lead you to useful information.

Lee KA0FPJ


Yes Lee, Google found quite a lot of hits, but they all refer to one 5band
antenna design with no much
real information. So my question still remains open. Could some modelling
program give the answer?
I think those two alternatives differ at least in how much inductive loadind
they are causing to the lower frequency
and so shortening the total length of antenna.

Jouko OH5RM

Linear decoupling traps
 

On Tue, 15 Apr 2008 11:39:04 +0300, "JN" wrote:



Jouko.......you might try to GOOGLE:

"lattin antenna"

That may lead you to useful information.

Yes Lee, Google found quite a lot of hits, but they all refer to one 5band
antenna design with no much
real information. So my question still remains open. Could some modelling
program give the answer?
I think those two alternatives differ at least in how much inductive loadind
they are causing to the lower frequency
and so shortening the total length of antenna.

Hi Jouko OH5RM

Yes modeling can give an answer:
NO

It does not work.

73's
Richard Clark, KB7QHC

Linear decoupling traps
 

Hi Jouko OH5RM

Yes modeling can give an answer:
NO

It does not work.

73's
Richard Clark, KB7QHC

Hi Richard,

Sorry I didnt quite understand your short answer.
What does not work? The whole principe of decoupling stubs?
Unfortenately I myself have no modelling program.

73 Jouko OH5RM

Linear decoupling traps
 

On Tue, 15 Apr 2008 19:48:53 +0300, "JN" wrote:

Hi Jouko OH5RM

Yes modeling can give an answer:
NO

It does not work.

73's
Richard Clark, KB7QHC

Hi Richard,

Sorry I didnt quite understand your short answer.
What does not work? The whole principe of decoupling stubs?
Unfortenately I myself have no modelling program.

Hi Jouko,

Basically, what you describe was discussed here last week as the W9INN
dipole, and recently as the Lattin dipole. Being the same thing as
your twin line (parallel line, or folded stub, or whatever); the
premise is these elements resonate and thus trap an antenna for
multiband operation. Those stubs are not oriented correctly.

Let's take this by degrees. Any dipole is a multiband antenna. Those
bands might be useful, and they might not. The point is that being
multiband is nothing remarkable in itself. What is remarkable is if
that antenna is useful in every band you want to use it in. This is
the "Holy Grail." Nearly 60 years ago, a Ham invented the Lattin
antenna. We cannot say it was designed because it never performed
according to claims (and I do mean NEVER). It was even patented.

Designs do work, inventions rarely do. We get inventors here every
week, some hang around for years. The bottom line is that if these
inventions worked, we would be using them (and that is 2% of the goal
of these inventors, the other 98% is seeking validation as being
eminent thinkers). The Lattin antenna's balance sheet shows 1PPM
usage, and no pursuit of validation (the inventor is dead, but some
still keep the vigil and change the flowers at Internet memorial
sites).

You can try your hand at modeling by visiting:
http://www.eznec.com/
The Lattin design is easily constructed by a model, I've done several
dozen variations. You can also model stubs that are oriented
correctly and that will work.

73's
Richard Clark, KB7QHC

Linear decoupling traps
 

Richard thanks for your answer and opinions.
I am not talking abt Lattin or W9INN.
These are things I hear in this thread for the first time.
I am talking abt using 1/4 wave stub as decoupling element
to make a (reduced size?) two band antenna.

This principle is used in commercial antennas like HY-GAIN AT-18
tower vertical and many others, stubs in line with element.
Orr in his antenna book is using orientation, open to center.but in line
with the element
So I am sure the principle works ok, and I was asking abt the different
orientation
alternatives. I understand that you would suggest 90 degree?
But does it really matter?

Designs do work, inventions rarely do. Yes I agree.
Therefore I am not going to build any complex mess where everything is
hanging of everything, just simple one time decoupling the element for
higher fequency.

73 Jouko OH5RM

Linear decoupling traps
 

Richard Clark wrote:
The Lattin design is easily constructed by a model, I've done several
dozen variations. You can also model stubs that are oriented
correctly and that will work.

Modeling real-world lossy stubs seems to violate
EZNEC's guidelines. How does one do it?
--
73, Cecil http://www.w5dxp.com

Linear decoupling traps
 

JN wrote:
So I am sure the principle works ok, and I was asking abt the different
orientation
alternatives. I understand that you would suggest 90 degree?
But does it really matter?

The series stub can be coiled in a circle
as a lot of commercial antennas do.
--
73, Cecil http://www.w5dxp.com

Linear decoupling traps
 

On Tue, 15 Apr 2008 21:44:02 +0300, "JN" wrote:

I understand that you would suggest 90 degree?
But does it really matter?

Hi Jouko,

At right angles, yes. Does it matter? That depends on proximity to
other conductors, including itself if you "coil" it around the
radiator, or along the radiator.

When I looked at your first posting, I was confused by the single
wire, and the text graphics should have been done in fixed font.

Keep the line conductors at least 3, preferably more, wire diameters
from the radiator or themselves. Use the largest diameter for the
multiplier of 3 (or more).

73's
Richard Clark, KB7QHC