[Elecraft] Balun at input or output of tuner

[Paul Christensen]

> This is 41.2 W per foot
> and at that level the RG-213 would get very warm and could even melt,
> especially if the choke were confined in a small box with no circulation 
> of
> cooling air.

If a balun of like reactance were instead wound in bifilar fashion using two 
parallel wires, rather than coax, wouldn't "additional loss due to mismatch" 
be less when compared to coaxial-wound types, assuming that the bifilar 
winding choke offers lower matched and mis-matched loss, much like open 
lines?  However, the bifilar winding is not really like a wide 
conductor-separated transmission line so, perhaps mismatch losses are less 
than the same length of RG-213, but more than open or balanced lines.  Most 
of the coaxial-wound baluns I've seen of the W1JR type, have been designed 
where the output Z much more closely matches the characteristic Z of the 
coax used for the winding (e.g., CM chokes used as line isolators between 
the transmitter and amp, or monoband dipoles at the feed-point).

I've never seen a coaxial-wound balun at a tuner output (within the tuner), 
only bifilar types -- although I know so-called "remote baluns" exist that 
do use coaxial turns.   Your example of the "remote balun" shows some 
startling, but realistic loss when using a tuner and traditional wire 
antennas for multiband HF operation.  If the losses are really that bad, 
then it's the tuner that should be remoted, not just the output balun.  So, 
it would be an interesting exercise to look at the mis-matched losses under 
the two Z extremes when using a bifilar type and use this as a closer 
approximation of loss for current choke/baluns placed inside the tuner, at 
the output terminals.

Paul, W9AC