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The Challenge: Make a Transmitter and Receiver



How did we send our message?

The buzzer sparked quite a lot but it was a bright white spark: lots of heat and light but not much radio energy. The high voltage output from the transformer was blue. The radio could pick up the buzzer spark but the high voltage output spark was louder.

When the Morse key was held down the buzzer buzzed, the current pulsed to the transformer which stepped up the voltage to several hundred volts producing a nice bright spark. The radio waves created by the spark (arc) were then radiated by the antenna which was connected electrically to the arcing terminals (saw blade) of the output of the transformer. Often we found that we could not get a reliable arc (probably due to the humidity), so we wired the output from the transformer (using a common connection) onto the buzzing switch which created a lovely reliable blue arc.

Buzzer circuit