- Cardboard tube (about 12 inches long and 2 inches in diameter)
- Copper wire (about 30 feet of 18-gauge wire)
- Diode (1N34A or similar)
- Capacitor (0.001 microfarad)
- Earbud speaker
- 9-volt battery
- Small breadboard
- Jumper wires
Instructions:
1. Wind the copper wire around the cardboard tube in a single layer, spacing the turns about 1/4 inch apart. Leave about 6 inches of wire at both ends of the coil.
2. Connect one end of the wire to the positive terminal of the battery.
3. Connect the other end of the wire to the cathode (negative) terminal of the diode.
4. Connect the anode (positive) terminal of the diode to the center terminal of the capacitor.
5. Connect the other terminal of the capacitor to ground (the negative terminal of the battery).
6. Connect the positive terminal of the speaker to the positive terminal of the battery.
7. Connect the negative terminal of the speaker to the ground (the negative terminal of the battery).
8. Place the radio near a strong AM radio signal. You should be able to hear the radio station through the speaker.
How it works:
The radio works by converting the radio waves into electrical signals. The copper wire coil acts as an antenna, picking up the radio waves and converting them into an electrical current. The diode rectifies the current, turning it into a DC signal. The capacitor filters the DC signal to remove any noise. The speaker converts the electrical signals back into sound waves, which you can hear.