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Old March 30th 06, 03:11 AM posted to rec.radio.amateur.antenna
John Popelish
 
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Default what a 1:1 choke balum used for

Jerry Martes wrote:
"John Popelish" wrote in message
...

wrote:

John Popelish wrote:



SNIP

At low frequency, I understand how this is a good approach (though this
discussion was about the W2DU style choke balun). But at higher
frequencies, I am concerned that the turn to turn capacitance might
provide a low impedance path that parallels the choke. A string of beads
does not have this problem.




Hi John

"For what its worth", I have wounf the coax around a single ferrite toroid
with the exact amount of turns and spacing so the impedance along the
conductor of the coax outer shield was maximum, as in parallel resonance.
I cant claim that it does any better job than any other "1:1 balun", but it
worked for me.
My point is - The turn to turn "stray" capacitance doesnt necessarily have
to be a source of performance degradation.


I think of it as more of a upper limit. Once you are above resonance,
the choke action has to drop. And if you are using one of the low
frequency ferrites, the resonance isn't going to be anything to write
home about either. ;-)