Highland Ham wrote:
Roy Lewallen wrote:
Good advice. In antenna applications, we need to strive to keep the
flux density low enough that ferrites behave essentially linearly. If
we don't, harmonic generation will result.
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A question : Is the above the reason why current baluns wound on a
ferrite toroid with ,say, a total of 10 windings , can be best made by
having 5 windings wound in 1 direction and the other 5 in the opposite
direction ?

No.

You probably mean "regressive" winding, where you wind half the turns,
cross the wire to the other side of the core, and wind the remaining
turns in the other direction (but the same sense) around the core. If
you wind half the turns in each sense (half where you pass the wire
downward through the center of the core each turn and half where you
pass it upward), you'll end up with nearly zero impedance and a very
poor balun.

The advantage of the "regressive" winding technique is that it reduces
the end-to-end capacitance of the winding. I've found that with high Q
inductors (but ones operating well below self resonance) it typically
improves the Q by around 10 - 15% or so, which is usually not worth the
trouble. With the sorts of ferrites commonly used for baluns, Q is
typically one or less over the operating frequency range, so
"regressive" winding makes no difference at all. In any case, it makes
no difference in core flux density.

Roy Lewallen, W7EL