Bandwidth of CW modulation (morse code)?

Question

How can I relate the bandwidth required by a morse code signal over RF to:

the length of a dash, and the length of a dot
the time between dots and dashes
the speed of keying?

Are all applicable to the bandwidth of the channel? Can I model this as a function?

The OP has added that the carrier is RF, which wasn't clear before... I thought it could just be a wire. — George Herold, Jul 22 '14 at 12:44
Duplicate? Where? The related thread linked is my own thread, and it is a different question. What I'm asking here wasn't answered there. — Ken - Enough about Monica, Jul 22 '14 at 12:50

score 1 · Answer 1 · answered Jul 22 '14 at 09:05

1

On off keying of a carrier with a rectangular pulse would occupy a bandwidth (to the first sidelobe in the sinc function spectrum) of 2/T where T is the pulse width. From this you can determine the bandwidth occupied by a dot, a dash (3x dot duration) and the space between symbols (which is the same as a dot).

answered Jul 22 '14 at 09:05

John

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Why is there bandwidth occupied by the space between symbols? – Ken - Enough about Monica Jul 22 '14 at 09:37
Also, is the maximum bandwidth when a rectangular pulse is used, or will non-rectangular waveforms (as generated by humans and real radios) occupy more? – Ken - Enough about Monica Jul 22 '14 at 09:37
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Typically, real radios use RC time constants or similar to drive pulse shaping and so occupy substantially less bandwidth than "hard" keying would, but there is a tradeoff in intelligibility. – Chris Stratton Jul 22 '14 at 16:23

Bandwidth of CW modulation (morse code)?

1 Answers1