How to Build a Simple Wireless Transmitter

Written by bob romanov
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How to Build a Simple Wireless Transmitter
A telegraph key allows user input. (Jupiterimages/Photos.com/Getty Images)

Building a wireless transmitter is a fantastic introduction to radio electronics. It is an inexpensive project, but uses similar technology to was used in vintage Morse code transmitters. This is a satisfying project because, though it is relatively simple to build, it creates a result that affects other pieces of technology. It is not just a circuit. It generates a signal that can be received.

Skill level:
Moderate

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Things you need

  • Short length of wood board
  • Drill
  • 2 dowels, 5 inches
  • 1 yard 25 gauge magnet wire
  • Telegraph key
  • Screws
  • Screwdriver
  • 555 IC
  • Solderless breadboard
  • Jumper wires
  • 10uF capacitor
  • 2.2k Ohm resistor
  • 220uF capacitor
  • Battery
  • Battery holder

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Instructions

    Antenna and Telegraph Key

  1. 1

    Use the board as the base.

  2. 2

    Drill two holes the size of the dowels into the base about 2.5 inches apart.

  3. 3

    Insert the dowels into the holes.

  4. 4

    Wrap the wire around both the sticks together.

  5. 5

    Screw the telegraph key onto the base.

    Breadboard

  1. 1

    Place the 555 IC in the breadboard.

  2. 2

    Select one rail to be the ground rail and the other to be the power rail. This is an arbitrary choice. The rails are the long and outermost rows on the breadboard.

  3. 3

    Connect a jumper between IC Pins 2, 6 and 7.

  4. 4

    Connect a jumper between Pin 1 and the ground rail.

  5. 5

    Connect the 10uF capacitor (C1) between Pin 2 and the ground rail.

  6. 6

    Connect the resistor (R1) between Pin 7 and the power rail.

  7. 7

    Connect a jumper between Pin 4 and the power rail.

  8. 8

    Connect the 220uF capacitor (C2) between the ground rail and an empty row.

  9. 9

    Screw the breadboard onto the base.

    Final Connections

  1. 1

    Connect one end of the antenna wire to Pin 3.

  2. 2

    Screw the other end to the telegraph switch.

  3. 3

    Run a jumper between C2 and the unused telegraph switch terminal. Screw it on.

  4. 4

    Connect the red battery lead to the power rail, and the black lead to the ground rail.

  5. 5

    Put battery into the holder and screw the holder onto the base.

    Operation

  1. 1

    Place the transmitter near a radio.

  2. 2

    Turn the radio to AM.

  3. 3

    Hold down the telegraph key.

  4. 4

    Tune the radio to the signal.

  5. 5

    Tap the key to turn the transmission on and off.

Tips and warnings

  • The FCC prohibits unauthorised broadcasts. Do not allow your transmitter to interfere with anyone else's radio reception.

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