overview: We created a simple crystal radio inspired by the following website http://www.crystalradio.net/cub_scouts/index.shtm... Materials: piece of wood/cardboard
4 in piece of one inch diameter PVC pipe
large paper clip
30-100 ft of antenna wire
27 feet of copper wire, coated
drill 1 N34A signal diode
47000 ? carbon resistor
Test results - We attempted to use this radio both inside and outside, outside worked better; it allowed more white noise and almost voices to come through. The voices get louder as you silence the people around you and create a web of wire to nest yourself in. We would suggest having closer to fifty feet of antenna wire to get stations more consistently.
Radio waves alter the electric and magnetic fields around the antenna, moving electrons between it and the ground. The coil (whose length is effectively adjusted by the movement of the paper clip) acts as a capacitor which charges and discharges at a resonant frequency corresponding to the frequency to which the radio is tuned, enhancing the desired signal and discarding the others. The diode converts the signal to an intermittent direct current at the frequency of the radio waves whose average intensity over short periods of time affects the movement of the speakers, thus decoding an amplitude-modulated signal.
Step 1: 1. Drill a hole a half inch from the end on each end of the PVC pipe.
Step 2: 2. Coil the coated copper wire around the PVC pipe so that coils touch but do not overlap, leaving 2-3” of uncoiled wire threaded through the holes at each end.
Step 3: ?Using sandpaper, sand away the coating on the copper wire in a roughly inch-wide strip on one side.
Step 4: Tape the PVC pipe and coil to the wooden board
Step 5: Unwind the large paperclip and bend it into a slight S shape. Create a hook at one end and a loop at the other.
Step 6: Cut one three and six inch piece of wire from the left overs piece from step four.
Step 7: Connect one end of the three inch wire to one end of the coil.
Step 8: Connect the alligator clip to the end of the three inch wire.
Step 9: Connect the loop of the paper clip to the other end of the 3-inch wire and to a 6-inch piece of wire. Tape the wires down securely so that the end of the paper clip can move freely along the coil of copper wire.
Step 10: Connect the antenna wire to the other end of the coil.
Step 11: Connect a short wire to both the antenna wire and the end of the coil. Connect the other end of this wire to the diode.
Step 12: Use additional wire to connect the diode to one end of the ceramic earpiece- note: there is a plastic piece partway up the earpiece, the wire needs to attach to one side of this.
Step 13: Connect the wire from the paperclip to the other side of the plastic piece, putting a plastic sheet between the two.
Step 14: Connect the resistor to the ends of the wires on either side of the ceramic earpiece.