Gene Fuller wrote:
Hi Roy,

Sorry about making such a mess. That tar is really hard to clean up.

FYI, I was referring mostly to Sevick's 4th edition of Transmission Line
Transformers, published in 2001. As you mention, he has undergone a
considerable transformation (pun intended) since his earliest books.

I'm glad to hear that. The first edition sold a lot of copies and
contained a lot of misinformation. The second was better, and hopefully
undid a little of the damage the first did. Maybe the net result was
neutral by the time the fourth was published.

Sevick does indeed recommend a two-core approach for a 4:1 Guanella
balun if the load side is not balanced.

That's one of those improvements over the first and second editions.

As you know, he generally avoids
the use of the terms "current balun" and "voltage balun".

Yes, I think that's mostly because they're the terms I coined and used.

My question still holds, however. In a typical situation the "balanced"
side, generally the antenna, is only partially unbalanced, not simply
shorted to ground on one side. In this generic case would you expect the
single core Guanella balun to perform poorly with slight or modest
imbalance?

I'm sorrry, I don't know, because I haven't looked carefully at his
"Guanella" balun to see if it's a current balun, voltage balun, or
something in between. As I pointed out in my balun article many years
ago, if an antenna is perfectly symmetrical, voltage and current baluns
perform equally. If it isn't, the voltage balun can make things even worse.

If both sides of the transformer are completely unbalanced it is not
clear why one would expect a balun of any type to be useful. What is
needed in that case is impedance transformation, not balancing.

Have you read the article at
http://eznec.com/Amateur/Articles/Baluns.pdf? If you have but still
think that, then I certainly failed to communicate.

For the benefit of readers who have read the article, I didn't mention a
second source of imbalance: mutual coupling to the antenna. This can
occur if the feedline isn't run completely symmetrically relative to the
antenna. And, interestingly, there are situations where this is
occurring that inserting a balun can actually increase the common mode
current. That's a story for another article some day. But first I've got
to somehow get people to read the first one.

Roy Lewallen, W7EL