I also made a mistake in that I failed to qualify my statement. I meant
only transmission line transformers. A conventionally connected
transformer will act as a current balun, and any ratio can be made with
a single core. However, it's difficult to get the extreme wide band
qualities from one that you routinely get from a transmission line
transformer. I don't agree with Trask that his design is a transmission
line transformer despite the two holes, but it does seem to have very
good bandwidth. Also, although he looked at the return loss with various
output terminals grounded, I don't see any measurements showing how well
it actually balances the output currents. But most conventional
transformers do a good job of that, so this one probably does.

Roy Lewallen, W7EL

Larry Benko wrote:
Whoops, my mistake. A single binocular core which obviously has 2
holes. Sorry

Larry, W0QE


Larry Benko wrote:

Roy,

Take a look at http://home.earthlink.net/~christras...k4to1Balun.pdf
for a supposed 4:1 current balun on a single hole torroid. I have no
first hand experience with this design.

73,
Larry, W0QE



Roy Lewallen wrote:


I don't know of any way to make a 4:1 current balun with a single
one-hole core. I think it's possible with a two-hole (binocular) core
if done right.