Roy Lewallen wrote in
:


As you say, though, there are always tradeoffs. A higher magnetizing
current means a lower winding impedance. In a winding connected across
a transmission line, this means adding a relatively low shunt
impedance across the line. In a series connected winding, as in a
current balun, it means less effective choking of common mode current.
Maximizing winding impedance, which also minimizes magnetizing
current, is always beneficial. But as we've both pointed out,
sometimes we're forced to choose a material that gives us less
impedance in order to lower the loss to a level that won't cause a
problem at high power levels. The price is a smaller shunt winding
impedance or less effective common mode choke, and also typically a
narrower operating bandwidth.

Yes Roy, and none of this has visited impedance transformation... or the
departure from ideal transformation that is envisaged by many if not most
buyers. Choices for magnetising current and the TL Zo in my model of the
R balun affect transformation at the upper and lower frequencies.

I know you have pointed out many times that shunting an antenna feed
point with a resistor may improved system efficiency. At least one
antenna manufacturer uses a lossy ferrite transformer to tame system
efficiency in a wideband antenna... the CHA250 comes to mind.

Owen