What is CW?

In amateur radio, CW stands for 'Continuous Wave.' It refers to an unmodulated electromagnetic wave that is turned on and off to carry information. This simple on-off keying is the standard method used for transmitting Morse code. While the acronym might sound to a newcomer like a type of digital mode or error correction ('Code Words'), CW is strictly the emission type used for traditional Morse code communication. It remains highly popular because it requires very little bandwidth and can often be decoded by ear even when signals are extremely weak.