"johan aeq" wrote
So a simple "pi filter" withe a bulun will do the same?
I always thought that the wide impedancerange of open wire made a
currentbalun or voltagebalun unusable.
I was just gathering parts to build my own balanced tuner....
Greetings Johan PE1AEQ

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All kinds of peculiar things can happen with voltage baluns and
current baluns which have a definite impedance ratio.

But my comments apply to a CHOKE balun, the most simple form of balun.
It is a pair of wires wound together on a ferrite ring. It is just a
very short 2-wire transmission line. For longitudinal currents it is
an RF choke, the 2 wires being effectively connected in parallel.

The impedances between which it can work are indeterminate. There is
no impedance ratio.

When connected between a balanced line and an unbalanced tuner, the
tuner can be an ordinary simple L, Pi or T network.

If you happen to have a balanced tuner, lying around doing nothing,
then by all means use it without a balun. But if you don't have a
balanced tuner, as is very likely, there's no need to make one. Just
use a common or garden unbalanced tuner, which nearly everybody has
already got, with a CHOKE balun.

The hardest part of making a choke balun is obtaining the ferrite
ring. 50mm outside diameter, 30mm inside diameter, permeability
200-400, about 16 turns of twin, flexible, stranded, speaker cable,
will be OK for the HF bands. Or similar.

All the very best for 2006.
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Reg, G4FGQ.