Last weekend I had occasion to read some material authored by Jerry Sevick.
("Building and Using Baluns and Ununs", Jerry Sevick, W2FMI, published by CQ
Communications, Inc.) In that document he states that the bead baluns (W2DU
type) may not be as effective as people think. This is part of Chapter 1,
Section 1.3, in which he reviews the amateur literature on baluns from about
1968 until recent times. He has technical reservations about much of what
has appeared in print over the years and explains why he has those
reservations.
Sevick suggests that the same result or better results can be obtained by 10
turns of Teflon coax wound on a single toroid. He references an article by
W1JR which appeared many years ago in Ham Radio.(September 1978). Reisert
(W1JR) wound half the turns on one side of the toroid and then crossed the
coax over and wound the balance of the turns (with the same flux 'sense') on
the other side. This allows one to have the input on one side of the toroid
and the output on the other.
Such a balun is really a Guanella balun, but is often called a "choke" or
"current" balun.
What Sevick says makes sense to me (I previously have been a 'bead' person).
Others may wish to read and decide for themselves.
I am not really familiar with the W0IYH baluns so this in not intended to
comment on them, only to call attention to some easily available material
which can be studied by those interested.
Tod Olson, K0TO
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