crystal radio: the first real free energy device

[franco malgarini]

With speaker:







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[pomodoro]

I have just built a simple crystal radio for OU research.  Its simply a tuned 'tank' LC , a germanium diode, a capacitor (0.01 for audio  or 10uF for DC), a piezoelectric earpiece and a 56k resistor across the 0.01uF cap as a load  for audio.
I'm 25km from the AM transmitters.  Using a ferrite rod antenna as the tuning coil only doesn't work well, so an external wire antenna 20 feet long is coupled to the ferrite using the smaller winding normally found on ferrite antennas. The other end of the winding is connected to the water pipes for a good earth.
I can get 1.3V on the 10uF capacitor and no load resistor, it takes time to charge (seconds). Without the tuned circuit, and just a diode there is practically no charging of the capacitor.  Quite amazing, as you would initially think that many more radio waves would be rectified by the diode, instead of just one signal. The large Q of the tuned circuit builds up the voltage for the frequency being tuned.
Power wise only 2-4 micro watts are available at the best load of about 70k. Voltage drops way down, below 1 volt.
The reason I built this crystal set is to try doped (radioactive) galena diodes and small transistors exposed to uranium oxide.  Moray is said to have used similar diodes in a crystal set. The result, apparently, was enough power to make 2000 ohm 1920's horn speakers  usable.

The circuit you describe would only work loudly when quite close to the transmitter. Otherwise there is simply not enough signal.
My simple circuit is actually able to power an 8 ohm speaker directly, but you need to put your ear right next to speaker to hear the whisper!
An  impedance transformer, like the one in your diagram, made the volume very slightly better. 

[franco malgarini]

Good antenna for crystal radio is better:

http://www.dummies.com/how-to/content/electronics-projects-how-to-add-an-antenna-to-a-cr.html





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[TinselKoala]

I just use a Slinky spring toy strung across the ceiling of my room as an antenna. This baby picks up enough power from the radio stations to make a green LED light up on the output, at certain times of the day. Not brilliantly but surprisingly bright anyway. The fidelity of the audio is remarkably good, using a piezo element in a plastic spicecup housing or a high-impedance magnetic earphone. I have a potted chunk of lead galena, tickled by a bit of phosphor-bronze wire from an old guitar string, or optionally a 1n34a germanium diode. When you get the right spot on the galena it works better than the diode.

[pomodoro]

That's a sweet looking set! Damn clever coupling system too.   I have a slinky somewere ... I've made only two batches of synthetic galena , undoped and set in woods metal.
In the lab, using a nearby signal generator , they produced less voltage on the cap when compared to the diode. I used a very thin strand of copper as the whisker. Any pressure at all and it conducted both ways. I need to try them on a radio signal to be certain before I change the synthesis. Do you need any pressure on your galena? Also, have you measured any shorted I or open v from the galena