The last chapter.

There's yet another point in favour of twin-balanced line rather than coax
for a choke balun.

As previously stated, the length of line wound on it is best not allowed to
exceed about 1/8-wavelength at the highest frequency of interest at the
line's own velocity factor.

Solid polyethylene coax has an appreciably lower velocity factor than twin
line such as figure-of-eight speaker cable. Or two separate wires wound
alongside each other.

Consequently, for the same length of balun line in wavelengths, more
twin-line turns can wound on the ferrite core than coax turns. This
increases LF inductance and extends the lower frequency downwards.

Or alternatively, with a shorter physical length of line on the balun, the
higher frequency is extended upwards.

The usable bandwidth of the twin-line version therefore increases roughly in
the ratio of the two velocity factors.

A choke balun may indeed be amongst the most simple of radio components to
construct - its true complexity being hidden.

But as always with radio, almost anything will work!
----
Reg, G4FGQ