Help...Bifiller

I need to know what a bifiller coil is...I came across it in a BALUN (Balance to unbalance coil)...It's construction...

What are it's advantages over an Inductor type coil ?


Thanks in advance...

Bifiller (bifilar) mean: two wires winding parallel. Advantage: exatly similar inductivity.

or:

wound on top of each other

When we made bifilar windings in the lab, we doubled the wire (put the two ends in a vise so there was a loop at the other end) and used a hand drill with a bent nail in it to twist the wires. Then the twisted wire was wound on the core. Then we cut the loop and used an ohmmeter to determine which ends had continuity.

Sebi said:

Bifiller (bifilar) mean: two wires winding parallel. Advantage: exatly similar inductivity.

Click to expand...

If resistance wire is used, then shorting together AB at one end and using the A and B at the other end for connections, makes a non-inductive wire-wound resistor.

It's my understanding that in a balun the pair of wires (bifilar) should have a characteristic impedance that equals the output impedance of the transformer. In books by Jerry Sevick and others, great pains are taken to design or create the pairs with the proper characteristic impedance. Quite often a pair of magnet wires isn't quite right so a layer of electrical tape (special high voltage in some applications) is added - sometimes thin plastic tubing works as well. I do not know what twisting does to the characteristic impedance. In all cases, Sevick's designs show wires layed flat, side by side, taped together - not twisted.