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The Challenge: Make a Transmitter and Receiver

How did we make our transmitter on the island?

The Rough Science transmitter had the following parts: 12V car battery, Morse key switch, buzzer and transformer mounted on a wooden board and an antenna.

The Morse key is a switch that connects and disconnects the 12V power to the rest of the circuit. It has a wooden knob on the top, which makes tapping out the Morse code easier.

The buzzer consists of an electromagnet (made from a nail wound with a coil of wire) with a saw blade switch forming the buzzer device. The saw blade switch has two connections: one connected at the fixed end and a second made by a screw contact on the flexible section. The screw could be adjusted to get the best contact. In a very crude way the screw also sets the buzzing speed and therefore the pulse frequency to the transformer. The interrupted current from the buzzer then went into the primary coil of the step-up transformer. The transformer was made by winding about 100 turns of thin insulated wire onto a bundle of iron nails and then the much thinner insulated secondary was wound on top of this — about 10,000 turns.

Buzzer circuit