The Good Curriculum

Education for Everyone

Adventure Science: Radio & Electronics Section

Lesson 4: The Crystal Radio

Learning Objectives:

  1. Learn how radio waves carry information
  2. Learn how radio receivers and transmitters work
  3. Learn what you need to build a crystal radio

First, read this article on how radio waves carry (transmit) information.

 

Now it’s time to start planning for your radio project. I want you to build a crystal radio receiver. Here is how:

Materials:

  • Two 6×6 pieces of aluminum foil
  • Paper towel role
  • Masking tape
  • Sheet of paper (cut a 7×7 piece)
  • Insulated wire
  • Toilet paper role
  • 26 gauge copper wire or magnet wire (55 feet)
  • Scrap-wood
  • Screws and screwdriver
  • Empty metal paint can
  • Sand paper
  • 1N34 germanium diode
  • Earphone
  • Xacto or utility knife

Assignment:

Start gathering materials for your crystal radio project. Look for these parts at a local electronics store or online. Options: mouser.com, mcmelectronics.com, candhsurplus.com, and alliedelec.com.

 

Extra:

If you decide to make the crystal radio receiver above (which I highly recommend), you will have a chance to build on this project. Here is what you will need if you decide to do this:

1. Build an Amplifier (speaker): lesson 22 (optional):

  • Two 10 microfarad (uF) electrolytic capacitors
  • One 0.1 microfarad (uF) ceramic capacitor
  • Two 220 microfarad (uF) electrolytic capacitors
  • One 0.047 microfarad (uF) ceramic capacitor
  • One 10 kilo ohm potentiometer (variable resistor)
  • One 10 ohm resistor
  • Simple on/off switch
  • One 9 volt battery
  • Battery circuit attachment
  • Small speaker (8 ohms works)
  • One LM386 amplifier chip or equivalent part
  • Amplifier chip socket
  • Perfboard
  • Solder and soldering iron
  • Plastic jar

Or you can build an earpiece amplifier: lesson 22 (optional):

  • One 0.001 microfarad (MF or uF) capacitor
  • Two 1 microfarad (MF or uF) capacitors
  • One 10 microfarad (MF or uF) capacitor
  • One 82 kilo ohm resistor (82k)
  • One 100 kilo ohm resistor (100k)
  • One 10 mega ohm resistor (82M)
  • One 2N4401 transistor or equivalent part
  • One 9 volt battery
  • Breadboard (for testing)

2. Build an AM Radio Transmitter: lesson 23 (optional):

  • One small transformer (audio or doorbell transformer)
  • One oscillator chip (for AM radio frequencies – 540 kHz to 1.6 MHz)
  • Sound source (CD player, iPod, etc.)
  • One mini male phone jack (1/8″ works)
  • Four 1.5 V AA batteries
  • Battery holder case
  • Breadboard
  • 24 gauge (AWG) wire or 22 gauge also works