How Does Morse Code Travel Long Distances?

Morse code first traveled as pulses of electric current along telegraph wires, then by radio, with shortwave signals bending off the upper atmosphere to reach across oceans. Its simple on/off signal is also very good at surviving long, noisy paths.

By wire

A telegraph is a battery, a key and a long wire. Pressing the key sends current down the line, and at the far end an electromagnet clicks a sounder.

Current weakens over distance, so long lines used relays: a sensitive magnet that detects the weak signal and switches a fresh local battery onto the next stretch of wire. Chain enough relays together and a message can cross a continent. The history page covers how the network grew.

By radio

On December 12, 1901, Guglielmo Marconi and George Kemp listened at Signal Hill, Newfoundland, with a wire antenna held up by a kite, and received signals sent from Cornwall, England. The signal was the Morse letter S, ....

That result showed radio could travel beyond the horizon, and it led scientists to propose the ionosphere: a layer of charged gas high above the Earth that bends shortwave signals back down. A signal can make several of these hops, which is how a small station reaches another continent.

Why Morse gets through

Narrow signal. CW takes up a tiny slice of spectrum, so the receiver can filter out most of the noise.
Concentrated power. All the transmitter's energy goes into one tone instead of a voice's spread of sound.
Easy to pick out. Your ear can find a faint, steady tone in static long after a voice has turned to mush. Hear it for yourself in the audio translator.