On Thu, 09 Dec 2010 11:33:27 -0800, Richard Clark wrote:

If the answer is yes, if I understand the schematic well, both of
variable capacitors are put one after the other inserted into the line.
The big question is how to make the variable inductance? Some wire wired
on a ferrite rod? (L ----------- A????) with a selector? Are the number
of half-loops means the number of turns?

Making the coil is easy. It is just bare wire. You connect leads
between various turns in the coil and a switch. A three to five
position switch will work. You can even wind separate coils and put
them on the switch so they add up in series as you turn the switch.

OK.

Even there, with a good
switching design you could use the same components to build them too.
(I am thinking of PI configuration, L, and so on).

What is the influence of these different configurations?

Some antennas (I am speaking of their wavelength, not style like
horizontal, vertical, end-fed, or other) are easier to tune with these
other styles, but the style offered in the link is fairly general
purpose.

I found a PI network tuner shematic.

Many thanks for the first steps help!

Sébastien.