Resonance: TK’s Australia Radio: Variometer Galena Crystal Set
Copyright notice: Audio from AM broadcast radio stations is heard in this video as example material for _radio tuning demonstration_. This is Fair Use for educational purposes and the audio content is only incidental to the demonstration. No copyright infringement is intended nor is any occurring.
The Australia Radio is actually a very old design, but I found an excellent example at
http://crystalradioclub.co.uk/g4wpw.htm
My external antenna is just a long wire about 30 feet long strung out to the eaves of the house. The ground is a copper pipe driven about 4 feet into the ground in a damp spot under the window air conditioner.
The lead galena crystal is of very poor quality and was gotten over the internet as a “rock collection sample”. I think a better quality crystal with good cubic fracture planes would probably work much better; at least it might be easier to find a good spot.
There is nothing special about the circuit, it is a basic crystal radio circuit, except I have a Green LED across (in parallel) with the audio output earphone connection.
When there is a strong station broadcasting at “daytime power” the LED will light up, and it does this without needing the crystal; it can be shorted and will still light the LED. The audio modulation doesn’t appear to be necessary for LED lighting. I’ve had the LED glowing brilliantly but very little audio, and I’ve had, as in this video, very good loud clear audio but no LED lighting.
I played with the turn count to get the frequency in the range I wanted. Originally it was picking up a powerful station at 760 kHz that swamped everything, so I wound up taking some turns off to raise the frequency so that this station doesn’t bleed over. But now I have the 1480 kHz station, also strong and nearby, bleeding over! However, I am ready to listen to CtC on a crystal set, like it should be heard.