How to Decode a Morse Code Radiogram

What a Morse Code Radiogram Is

A radiogram is a message transmitted with Morse code over sound or radio. The operator keys letters as short and long pulses, and the receiver writes the dots and dashes down before reading them back as text.

Because the signal is a continuous stream, the only thing separating one letter from the next is timing: a short gap inside a letter, a longer gap between letters, and a longer gap still between words.

Why the Split into Letters Matters

Morse code is not a prefix-free code: one letter’s pattern can be the start of another. The signal "...." is the letter H, but the same four dots could also be read as S then E, or as five other combinations, if the gaps are lost.

This is the heart of the classic textbook task: when the split into letters is unknown, you must restore it using the pauses and the known alphabet. Get the spacing right and the message is unique; lose it and the same dots and dashes decode many ways.

Decode the Radiogram Step by Step

First mark the gaps: separate the stream into letter groups by the longer pauses, then group letters into words by the longest pauses. Write a space between letters and a slash between words.

Then map each group to a character using the Morse alphabet, and paste the spaced sequence into the decoder below to check your answer instantly.

Check Your Answer with the Decoder

Type or paste the dots and dashes, keeping one space between letters and a slash between words, and the decoder returns the text. If a group shows as unknown, the spacing is off — usually a missing or extra gap.

The iOS and Android app goes further: it plays a radiogram as audio at a set speed and can decode Morse it hears through the microphone, so you can practice receiving by ear, fully offline.

Try the Morse translator

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