I have dug out of my box an old 1:1 balun I wound several years ago,
possibly to a design in to the ARRL Handbook or the Antenna Handbook neither
of which I sill have. This was wound with the main winding bifilar on one
half of the (BIG) core and the third 'magnetising' winding on the opposite
side of the core.

I can find many balun designs using just the bifilar pair and some with a
third winding trifilar with the first two but can't find reference to
separating the third winding. Can anyone shed any light on why I might have
done it this way. I'm sure it was recomended somewhere but my memory is
fading.......

I'm just curious to know why it was done as on a quick test with antenna
analyzer and 50 ohm carbon resistor as a load it seems to work well from
below 3 to 30 MHz. An oscilloscope shows the output to be well balanced.

73 de Dick G4BBH