EscapeVelocity

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Piggie

The question is how low is low? 0.5? 1.0?

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The more I understand, the less I know.

EscapeVelocity

0.2-0.5

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Don_M

As you know better than anyone, experimenting won't hurt anything.

Your main risk here is that the 4221HD may well have an impedance value that's different from the old 4221, and that CM probably designed the balun with the 4221HD's actual impedance in mind. CM probably kept the 3021/4221's impedance fairly close to 300 ohms so as to match twinlead and off-the-shelf coax transformers, but this isn't necessary when a built-in balun is part of the design. The greater the impedance mismatch, the more the antenna's gain will suffer. That's also insertion loss, at least indirectly.

EscapeVelocity

So the balun is specifically designed for the particular antenna's characteristics? Its not just a low loss 4 to 1 balun.

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Don_M

Ken Nist is a far better authority on the topic. His temporary page kinda sorta touches on this. He doesn't mention hard humbers, though, just ratios to 75 ohms.