My Crystal Radio in Action!

What is a Crystal Radio?

A Crystal Radio is a form of AM (Amplitude Modulation) receiver, invented before the dawn of vacuum tubes or semiconductor transistors. Actually, a Crystal Radio employs a primitive semiconductor diode called a "Detector" formed at the junction of where a brass wire, called a "Cats Whisker", comes on contact with the surface of a crystalline mineral called Galena. The most basic crystal radio consists of following components;

• Antenna - converts electromagnetic waves into alternating RF (Radio Frequency) current.
• Coil - Tuned circuit consisting of a coil and capacitance of the antenna to select a specific Radio Frequency to listen on.
• Detector - A device that only allows current to flow in one director, used to strip the RF envelope from the embedded audio signal. 
• Reproducer - A device that will turn alternating AF (Audio Frequency) current into sound. I use a high impedance piezoelectric crystal earphone or audio amplifier for this purpose.
• Ground - Offers a low resistance return path for the RF current in the turned circuit. In my case it is a connection to cold water pipe that is buried in the earth.

Below is a picture of my Crystal Radio made from modern components. I used the instructions from a Poof Slinky crystal radio I purchased to determine the number of windings and diameter of the coil. 

Click on the button below to download Poof Slinky Crystal Radio Instructions

Poof Slinky Crystal Radio Instructions

Crystal Radios on Amazon

The Crystal Radio Detector

Circled below is my Detector that consists of a brass wire, call a "Whisker", touching a piece of Galena crystal. I use alligator clips to hold the assembly together as you have to be able to adjust where the brass wire contacts the Galena for optimal audio volume.
I obtained the Galena from our local Natural History museum gift shop for 25 cents! Their  gift shop contained all sorts of interesting mineral samples including Galena.

In the early days amateur radio enthusiasts used to key or switch on their own "Spark Gap" transmitter and use that signal to adjust the Galena detector for maximum audio volume.

The Amplifier

I use a simple audio amplifier, based on the LM386 audio amplifier integrated circuit, to listen to the output of my Crystal Radio. I could have just as easily used a piezoelectric crystal earphone.

Audio Amplifier Kits on Amazon

Why do most Crystal Radio builds fail?

I see a lot of negative reviews of Crystal Radio kits on Amazon. I believe most Crystal Radio kit builds are epic failures in picking up radio stations is that builders don't appreciate the importance of a good antenna and ground. I get satisfactory  reception from my Crystal Radio because I connect it to a 102 Ft long G5RV dipole Amateur Radio antenna that I have hanging outside. In addition, the Crystal Radio is grounded to the main water line in my house, which is conveniently located in my Radio Shack. Unlike modern radios, no amplification is employed in a Crystal Radio and all power is derived from the incoming electromagnetic waves! While my antenna and ground setup may be overkill for a Crystal Radio, you still need a good antenna and ground to be able to hear radio stations.

Finally, my Crystal Radio in Action!

The YouTube video below is my Crystal Radio in action. You can hear a gospel choir from a religious radio station singing, if you listen closely.