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Does an UnUn decouple an antenna from the feedline?



 
 
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  #1  
Old November 27th 07, 04:57 PM posted to rec.radio.amateur.antenna
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Posts: 26
Default Does an UnUn decouple an antenna from the feedline?

Hi,

I am trying to figure out the proper balun to use on an Off Center Fed
dipole I am going to construct. I have settled on a 6:1 UnUn design
by Jerry Sevick, W2FMI. My question is will this properly prevent
feedline radition? Is some feedline radiation always expected /
inherit in this type of antenna design?

-Scott, WU2X
  #3  
Old November 27th 07, 06:05 PM posted to rec.radio.amateur.antenna
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Posts: 26
Default Does an UnUn decouple an antenna from the feedline?

Hah, ok that will be tough because it will be used on most HF bands.
But I think I have the solution. I will cover the coax from the
antenna feedpoint to the rig with #73 beads. That ought to do it

-Scott, WU2X

On Nov 27, 12:18 pm, Richard Clark wrote:
Then add another choke a quarterwave beyond that, and
possibly a third one a quarterwave further along.

  #5  
Old November 27th 07, 06:53 PM posted to rec.radio.amateur.antenna
Highland Ham
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Posts: 250
Default Does an UnUn decouple an antenna from the feedline?

I am trying to figure out the proper balun to use on an Off Center Fed
dipole I am going to construct. I have settled on a 6:1 UnUn design
by Jerry Sevick, W2FMI. My question is will this properly prevent
feedline radition? Is some feedline radiation always expected /
inherit in this type of antenna design?

=======================
In the past I have used an off-centre dipole with wire lengths ratio 1:2
(Windom) It had a 1:4 balun meant to transform the impedance from 50
to 200 Ohms. It worked quite well on the harmonic bands 80-40-20-10 m
The balun was obviously located at the dipole Tee.

Where would you locate a 1:6 unun ? I am eager to learn.
I also have Jerry Sevick's book :'Building and Using Baluns and Ununs'.
It is a treasure.

Frank GM0CSZ / KN6WH


  #6  
Old November 27th 07, 07:32 PM posted to rec.radio.amateur.antenna
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Posts: 26
Default Does an UnUn decouple an antenna from the feedline?

On Nov 27, 1:53 pm, Highland Ham
wrote:
Where would you locate a 1:6 unun ? I am eager to learn.
I also have Jerry Sevick's book :'Building and Using Baluns and Ununs'.
It is a treasure.


The balun I am going to use is the one from the book "Transmission
Line Transformers, Fourth Edition" Section 8.2.2: 50:300- Unun.
http://www.cwsbytemark.com/ sells it 69.95$, which is pretty fair
considering it comes in an alum. enclosure. I have the Buckmaster
commercial OCF ($$$$$) and I have never really been too happy with it.
I want to build myself a new version and also I have a bunch of people
I am trying to get started in the hobby and in my opinion, this is a
good starter antenna for HF.

-Scott, WU2X
 




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