[TowerTalk] Managing Balanced line transitions

Allan H. Kaplan w1ael at arrl.net
Fri Feb 2 16:19:28 EST 2007

I would recommend NOT using baluns in connection with open wire line.  
It's hard to guess what impedance they would see at a particular 
frequency location along the line, and they do not work well nor with 
low loss when they are mismatched.  In general, they will always be 
mismatched in your situation!  For the coaxial sections you contemplate, 
use one short coaxial cable for each side of the balanced line, tying 
the shields together at the ends.   Seal those ends against the 
weather.  These transitions maintain balance with relative immunity from 
proximity to external conductors.  You will have large mismatches at 
those junctions, which is why you use as little coax as will reach.  You 
will tune out the mismatch with a tuner in the shack anyway, so small 
consequences if any.   It's best to use a truly balanced tuner for 
balanced feedlines for the reasons mentioned above.   In such a 
well-designed setup, the necessary balun is at the INPUT of the tuner, 
contrary to manufacturers with a few exceptions.  Hope this helps and 
good hunting!  73 de Allan, W1AEL in Tennessee, USA.

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