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How to Make a Portable Radio

Radio building is a popular hobbyist activity. Hobby shops usually sale radio assembly kits appropriate for all levels -- from the preassembled beginner kits to the advanced kits that require total assembly. However, there are homemade options for portable radio building that beginners can try with materials found around their homes or that can be easily purchased at a local hobby store. One of the simplest portable radio types a beginner can build is the three-penny radio. In some cases, these radios can be built in less than 10 minutes and for less than $10.

Things You'll Need

  • Three pennies
  • Tuning coil
  • MK484-1 AM Radio Integrated Circuit
  • Piezoelectric earphone
  • Tuning capacitor
  • 100,000 ohm resistor
  • 1,000 ohm resistor
  • 0.01 microfarad capacitor
  • Two 0.1 microfarad capacitors
  • 1.5 volt battery
  • 1.5 volt battery holder
  • Glue
  • Razor blade
  • Tuning knob
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Instructions

  1. Assemble the Integrated Circuit.

    • 1

      Use clean pennies. New pennies work best, however; old pennies can be cleaned with brass polish or soaked in a vinegar and salt solution for 30 minutes. Wipe them clean and allow them to air dry.

    • 2

      Place the pennies, heads-side down, in a triangular position. For example, envision a compass, the pennies should be arranged in the west, south, and east positions.

    • 3

      Bend the wires of the integrated circuit so that the two outside wires are pointed outward and the middle wire remains straight (e.g. west, south, and east). The integrated circuit has a plastic bottom with a flat-side, usually marked "MK 484", and a rounded-side; and three metal wires that stick out the top. Place the flat-side down - this arrangement is important, because the "west" wire will serve as the output, "south" as the input, and "east" as the ground.

    • 4

      Solder each of the three wires of the integrated circuit to one of the pennies. Remember to keep the circuit with the flat-side down and the pennies in a triangular position. Also, note that pennies take longer to melt than some other melts.

    • 5

      Solder the left wire of the tuning capacitor to the bottom of the "south" penny. Be sure to place the capacitor with the face-down; that is, you should be able to see the bottom of the screws that hold the capacitor casing together. Note, you will need the second (center) leg of the capacitor; however, you can cut off the third leg if you want.

    Solder Capacitors and Resistors into Place.

    • 6

      Solder the 0.01 microfarad capacitor in place. This capacitor should be marked ".01M" and only has two legs. Solder one leg to the bottom of the "east" penny and the other leg to the center leg of the tuning compactor.

    • 7

      Solder the 100,000 ohm resistor in place. The resistor has colored bands that are black yellow and brown toward the center, and a wire that sticks out from both ends. Solder one end of the wire to the bottom of the "west" penny, and the other end of the wire on the center leg of the tuning compactor. Do not allow the wires from the 100,000 ohm resistor and 0.01 microfarad capacitor to over lap when soldering to the center wire of the tuning capacitor.

    • 8

      Solder the 0.1 microfarad capacitor, usually marked "104" or "0.1M", to the "east" and "west" pennies. This is done by stretching the wires of the capacitor over the integrated capacitor and soldering each wire of the 0.1 microfarad capacitor to the appropriate penny; however, make sure the wires from the 0.1 microfarad capacitor doesn't touch the wires from the integrated capacitor.

    Build and Mount the Resistor Assembly.

    • 9

      Build the resistor assembly. This is done by connecting the wires from the piezoelectric earphone to the 1,000 ohm resistor (which has colored strips and a wire at either end) and the other 0.1 microfarad capacitor together. Uncoil the cord of the piezoelectric earphone into two separate wires. At one end of the resistor, wrap one of the wires from the capacitor -- these should form sort of a T-shape. Wrap one wire from the earphone to the other wire of the capacitor (the bottom of the "T"), and the other earphone wire to the other end of the resistor. Solder each wire where you have wrapped them together, to be sure they don't come apart.

    • 10

      Solder the bottom of the resistor assembly (the side with the 0.1 microfarad capacitor) to top of the "west" penny.

    • 11

      Wrap the red wire of the battery older to the top of the resistor assembly and solder the wire into place. Solder the black wire to the top of the "east" penny.

    • 12

      Unravel about 6-inchs of wire from your both ends of the tuning coil. Solder one piece to the center arm of the tuning capacitor and the other wire to the other arm (the arm soldered to the penny) of the tuning capacitor.

    Prepare the Radio for Use.

    • 13

      Flip your radio over, penny-side up, and insert the battery.

    • 14

      Secure the components of your radio to a steady surface - like a board or the inside of a box, with glue or push pins. You can be as creative as you want. For example, you can glue your radio into a small jewelry box or hide it inside a hollowed out book.

    • 15

      Tune your radio to the desired station by installing a tuning knob on to the tuning capacitor. Use a razor blade to cut a small rectangular hole, slightly smaller than the brass rod on the top of the tuning capacity, in the center of a plastic top - such as an old prescription bottle top. Push the plastic top onto the brass rod, so that they fit snuggly together. You can now use this as your tuning knob.


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