Hello Sébastien,

This: http://www.tetech.nl/divers/Simple_HF_Preselector1.png will
help you. It shows the basic idea of a simple single variable
capacitor preselector.

You can use one coil and put two selectors on it, but with two
seperate coils the attenuation for out-of-band signals is much better.
This is because the individual turns of each coil have low mutual
coupling (they don't act as a transformer). As I have sufficient
antenna noise, the selectors (in my case clips) are mostly on the
lowest position (I don't need matching to get more signal and noise).

For AM BC operation you need more turns (w.r.t. the coils on the
photo).


Wim
PA3DJS
www.tetech.nl
without abc, PM will reach me in most cases.