Hi guys,

This is the circuit:


Now my question is if i am to build that circuit, i have to take a transformer, connect one end of the primary winding to the antenna and ground the other end????? Where do i ground it ???? Do i connect the variable capacitor to the secondary of the transformer??? And is that L1 the inductance of the secondary of the transformer ?

Thanks

 

That's the schematic of a simple crystal radio. Do a search for "crystal radio" or "crystal set". You will find a huge amount of information.

 

Hi guys,

This is the circuit:


Now my question is if i am to build that circuit, i have to take a transformer, connect one end of the primary winding to the antenna and ground the other end????? Where do i ground it ????

It needs to have a signal ground, otherwise there will be no path for the RF current. You could use the ground on a wall outlet. Or even just a chunk of metal. Or you could just hold that wire in your hand. It doesn't necessarily need earth ground, but it does need somewhere to get electrons from/send electrons to.

Do i connect the variable capacitor to the secondary of the transformer???

Yes, that creates a resonant "tank" LC circuit, which will be most sensitive to one particular frequency.

And is that L1 the inductance of the secondary of the transformer ?

That's correct. The transformer is not only being used as an "impedance match" for the antenna, but the secondary winding is being used as a resonant LC tank circuit.

It's a classic crystal set, as Ron H already mentioned. My grandfather made one of those around 1907 when he was growing up in NYC. I made one as a kid, too.

They still work - no batteries needed

 

Thanks guys