"Reg Edwards" wrote in message
...

"Antonio Vernucci" wrote
So, I decided to instead use an RF choke that quenches the common
mode
RF. I firstly built a thick ferrite core by taping together five
3/8"OD ferrite rods, 6-inch long. I then made 10 turns of a very
thick
insulated red-black twin lead on it. The turns are widely spaced, so
as to have low capacitance between adjacent turns.
=========================================

Congratulations. You have just re-invented the choke balun. It's
what
many people use. It is the best choice. Very often it is wound on
a
ferrite ring. It has no impedance or turns ratio.

Or it may consist of a number of ferrite sleeves which slide over
the
transmission line.

It is a mistake to use a balun between tuner and transmission line
which has a definite impedance or turns ratio.
----
Reg.

======================================
A further comment -

It may not be obvious, but a number of ferrite sleeves sliding over
the transmissiom line, either coax line or twin line, corresponds to a
single turn of line passing through an elongated ferrite ring.

The formulae for calculating choking inductance, from dimensions and
number of turns, is the same for one ferrite ring and a single or a
number of sleeves.

Obviously, there is more heavy, ferrite material used for sleeves
because the number of turns is only one. But disregarding economics, a
number of sleeves will eventually provide a better very-wide-band
choke than a ferrite ring or a bundle of ferrite rods.

Rich, intelligent, technical perfectionists, using high power, with
plenty of spare time, are the most likely people to win contests.
----
Reg.