Hello,

On Thu, 16 Dec 2010 09:40:15 -0800, Wimpie wrote:

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.

Many thanks. I will try it as soon as possible.

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).

OK.

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

As I want to use it from 0.5 to 30MHz, what would be size of both coils?
How many turns? What diameter? What would be the value of the C1
capacitor? A lot of questions....

Thanks again.

Sebastien.