HERE IS YOUR FREE ENERGY. HANDLE WITH CARE.

[Localjoe]

Hans i guess im more interested in the math or science behind what exactly makes the specific  crystal in a crystal radio optimum for that freq spread and what factors define it ...With that knowledge I would possibly pay a company to design ones to specs that would suit our needs or the freq spread i would like it to be reactive to meaning the uv or higher... So i guess thats what im hunting for.
                                                                                                                                              Joe

It doesn't Joe, the frequency is determined by the resonant circuit in front of it, the crystal is just a rectifier that blocks RF and lets LF through.



The coil and the variable condenser here make up the resonant circuit, the variable condenser allows you to tune to a specific frequency. There are other ways of doing it like with a variable coil but essentially it's as simple as this.

Hans

Alright now im confused .. lf is low freq mf is medium and hf is high freq .. doesent rf encoumpas at least one or two of those bands>?

[nightlife]

I can't think of how it can attract one and not the other unless it is created by one and not the other.

[hansvonlieven]

hansvonlieven, how does it block RF and let LF thru?

a galena crystal is a semiconductor or diode. It lets electricity flow only in one direction, so therefore blocks AC. RF is AC. The superimposed signal that is left is a DC component which passes through, hence the separation.

This is a rough and ready explanation but close enough to the mark.

Hans

@ Joe, think of the LF signal in terms of pulsed DC rather than AC

[nightlife]

hansvonlieven, well it sounds like we now have a filter we can use, are there any more like this?

[hansvonlieven]

What do you want to filter?

Hans