Howdy:
In a j-pole the 1/4 wave element, and the bottom 1/4 of the 3/4
element should act as a transmission line, right? So... shouldn't these
elements be as very close to each other to cancel one another out, closer
than what I see on most j-poles? Or is this space have something to do
with the impedance of the antenna?

--
SeeYaa Harbin Osteen KG6URO

This is YOUR futu
http://halturnershow.com/aztlan_caps.wmv
http://media.putfile.com/La-Gran-Marcha
The Mexican Solution:
http://www.centerforsecuritypolicy.o...s&code=06-D_18

-

On Thu, 4 May 2006 17:20:24 -0700, "Harbin"
wrote:

Howdy:
In a j-pole the 1/4 wave element, and the bottom 1/4 of the 3/4
element should act as a transmission line, right? So... shouldn't these
elements be as very close to each other to cancel one another out, closer
than what I see on most j-poles? Or is this space have something to do
with the impedance of the antenna?

Remember you are using wavelengths as your measurement. On 160-meters
6-foot separation would be okay.

Danny



In my many years I have come to a conclusion that one
useless man is a shame, two is a law firm, and three
or more is a congress. - John Adams

email: k6mheatarrldotnet
http://www.k6mhe.com/

Hello Harbin

The bottom of the J-Pole antenna is a 1/4 wave length to transform the high impedance of the 1/2 wave length above into a lower impedance (close to 50 ohms). The impedance of that 1/4WL sould be Z = SQUARE ( Z coax X Z antenna) .... in that case Z antenna is the impedance of the 1/2 WL (usually several hundreds ohms)
That's why the space between elements as well as there diameter is important.

You certainly know the Topfkreis ... which is the same antenna ... 1/2 WL + 1/4 WL ... but with another technical realisation.

Hoping it helps.

Regards

Jean-Marc
F4DRH
www.barbaxoops.com




"Harbin" a écrit dans le message de news: ...
Howdy:
In a j-pole the 1/4 wave element, and the bottom 1/4 of the 3/4
element should act as a transmission line, right? So... shouldn't these
elements be as very close to each other to cancel one another out, closer
than what I see on most j-poles? Or is this space have something to do
with the impedance of the antenna?

--
SeeYaa Harbin Osteen KG6URO

This is YOUR futu
http://halturnershow.com/aztlan_caps.wmv
http://media.putfile.com/La-Gran-Marcha
The Mexican Solution:
http://www.centerforsecuritypolicy.o...s&code=06-D_18

-

F4DRH wrote:
Hello Harbin

The bottom of the J-Pole antenna is a 1/4 wave length to transform the
high impedance of the 1/2 wave length above into a lower impedance
(close to 50 ohms). The impedance of that 1/4WL sould be Z = SQUARE ( Z
coax X Z antenna) .... in that case Z antenna is the impedance of the
1/2 WL (usually several hundreds ohms)
That's why the space between elements as well as there diameter is
important.

You certainly know the Topfkreis ... which is the same antenna ... 1/2
WL + 1/4 WL ... but with another technical realisation.

Hoping it helps.

Regards

Jean-Marc
F4DRH

Jean-Marc

Thanks for mentioning the Topfkreis. It seems like it should work much
better, and is so obvious once you see it. I will have to make one.

tom
K0TAR

On Sun, 07 May 2006 20:05:28 -0500, Tom Ring
wrote:



Thanks for mentioning the Topfkreis. It seems like it should work much
better, and is so obvious once you see it. I will have to make one.

tom
K0TAR


OK, I did a search, unsuccessfully, on Topfkreis. What is it and
where do I find it?

thanks
Buck

--
73 for now
Buck
N4PGW

Harbin,
You seem to understand the "J-Antenna". What you really seem to be asking is how far apart is "too far" for a balanced transmission line. That's a question I can't answer and I'm sure others can, but , in the common custom of adding obtuse references which sort of seem to be relevant... what about that old one wire transmission like the "G-Line"? [no joke]

73, Steve, K9DCI


"Harbin" wrote in message ...
Howdy:
In a j-pole the 1/4 wave element, and the bottom 1/4 of the 3/4
element should act as a transmission line, right? So... shouldn't these
elements be as very close to each other to cancel one another out, closer
than what I see on most j-poles? Or is this space have something to do
with the impedance of the antenna?

--
SeeYaa Harbin Osteen KG6URO

This is YOUR futu
http://halturnershow.com/aztlan_caps.wmv
http://media.putfile.com/La-Gran-Marcha
The Mexican Solution:
http://www.centerforsecuritypolicy.o...s&code=06-D_18

-

"Steve N." wrote in message ...


Harbin,
You seem to understand the "J-Antenna". What you really seem to be asking is how far apart is "too far" for a balanced transmission line. That's a question I can't answer and I'm sure others can, but , in the common custom of adding obtuse references which sort of seem to be relevant... what about that old one wire transmission like the "G-Line"? [no joke]

73, Steve, K9DCI


Hi Steve:
I have read about the G-Line, which is very low loss (so claimed). Have
you heard of anybody that has used this line?

Nope. Only read about it and, perhaps, understand the theory.
73, Steve, K9DCI

"Harbin" wrote in message ...
"Steve N." wrote in message ...


Harbin,
You seem to understand the "J-Antenna". What you really seem to be asking is how far apart is "too far" for a balanced transmission line. That's a question I can't answer and I'm sure others can, but , in the common custom of adding obtuse references which sort of seem to be relevant... what about that old one wire transmission like the "G-Line"? [no joke]

73, Steve, K9DCI


Hi Steve:
I have read about the G-Line, which is very low loss (so claimed). Have
you heard of anybody that has used this line?