1:1 / 4:1 baluns

[bob conley]

I'm showing my ignorance again!
What determines which balun you use
RC


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[Don Wilhelm-4]

RC,

The relative impedances will determine which type is best.  If at the
connection point of the balun output is a relatively low impedance (up
to 200 ohms IMHO) the 1:1 balun will usually serve better, but at higher
impedances, the 4:1 will be best.

Measure the actual impedance at the feedpoint with an antenna analyzer.  
remember that the impedance will vary depending on the antenna and the
length of the feedline.  Just because you use a feedline of 450 ohms
characteristic impedance, that has no relationship to the feedpoint
impedance which can vary from very low to very high.

If you have no access to an antenna analyzer, try them both and use
whichever tunes the best, and if the decision is a wash, use the 1:1
because it is usually a bit more efficient.

Another point is to use only the current (or choke, or bead) type balun
with a multiband antenna system - these types minimize common mode
current on the unbalanced side.

73,
Don W3FPR

bob conley wrote:
> I'm showing my ignorance again!
> What determines which balun you use
> RC
>
>  
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[w5tvw]

Whichever impedance transformation you want.  Depends on antenna being used.

One thing.  A balun becomes lossy when used to match a very reactive load.
If you have a load of say 300 ohms, a 4: 1 balun would be most suitable even
though there would be still a slight mismatch.  (It wants to see 200 ohms
with a 50 ohm output transmitter)

Again, although it will "work", try and avoid using a balun with a highly
reactive load, especially if you are running higher power!

73,
Sandy W5TVW
----- Original Message -----
From: "bob conley" <[hidden email]>
To: <[hidden email]>
Sent: Sunday, September 09, 2007 11:30 AM
Subject: [Elecraft] 1:1 / 4:1 baluns

> I'm showing my ignorance again!
> What determines which balun you use
> RC
>
>
>
> ____________________________________________________________________________________
> Park yourself in front of a world of choices in alternative vehicles.
> Visit the Yahoo! Auto Green Center.
> http://autos.yahoo.com/green_center/
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> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
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