Using any balun with an unbalanced tuner to feed balanced line can be
bad news (your mileage may vary, standard disclaimers apply). Under
highly reactive loads, a balun used like this can become quite lossy.
There's a couple articles in publications and on the Internet on this,
but Cebik's article is one that comes to mind (
http://www.cebik.com/link/l-bal.html ). It's better to run a real
balanced tuner like a Johnson Matchbox, the MFJ Balanced Line tuner, or
others, if you can.
Don Wilhelm wrote:
Curt,
There seems to be a misconception among hams that when using 450
ladder line, a 4:1 balun is the best thing to use. While that may be
true in some cases, in many other cases, a 1:1 balun will serve
better. It all depends on the feedpoint impedance of the feedline at
the shack end, and that has little relationship with the fact that 450
ohm line is being used - i.e. the feedpoint impedance is *not* the
characteristic impedance of the transmission line in most cases. The
feedpoint impedance looking into the shack end of a multiband antenna
can vary from extremely low to extremely high - it all depends on the
length of the antenna and the length of the feedline.
--
Blog: http://thek3ngreport.blogspot.com/
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