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Old August 15th 08, 02:01 PM posted to rec.radio.amateur.antenna
Edward Feustel Edward Feustel is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 39
Default 600 ohm balun vs 200 ohm balun

On Sun, 10 Aug 2008 11:32:24 -0500, Cecil Moore
wrote:

Edward Feustel wrote:
I am interested in opinions on whether it would be better for me
to use a 450 or 600 ohm balun that might more closely match the
transmission line (in practice).


450/50 = 9:1, 600/50 = 12:1 - Is that what you are thinking?

On a transmission line with standing waves, the impedance seen
by the balun will NEVER be the Z0 of the transmission line.

Let's say you are using Z0=600 ohm feedline with an SWR of 20:1.
Let's say a current maximum point exists at the balun. The balun
will see an impedance of 600/20 = 30 ohms.

Do you want to use a 4:1 balun and take it down to 7.5 ohms? Why?
Do you want to use a 9:1 balun and take it down to 3.3 ohms? Why?
Do you want to use a 12:1 balun and take it down to 2.5 ohms? Why?

Do you want to use a 1:1 balun and leave it at 30 ohms?

When the impedance being encountered by the balun is unknown,
a lot of experts recommend a 1:1 current-choke-balun.


Cecil,
I had never thought to try this!
I happen to have one that I was planning to use in a balanced tuner.
So I will try it and see how it wouks Practically.
Thanks.
Ed, N5EI