The Morse code

The easiest, and oldest, form of modulation is on-off keying. Early telegraph systems made use of direct currents which were keyed on and off, and were sent along the wires. The 1st radio transmitters employed spark generated hash signals which were keyed by using the telegraph code. The noise from sparks, like ignition noise from the car, could be heard in the crystal-set receivers many miles away. At the time when they were invented, this phenomenon was deemed miraculous.

Keying is accomplished at oscillator of a continuous-wave (CW) radio transmitter. A block diagram of the simple CW transmitter is shown in the figure given below. This is basis for the mode of communications that is, and always has been, popular among the radio amateurs and experimenters.

                                                                               Figure--A simple CW transmitter.

While the use of Morse code may seem quite old fashioned, even archaic, a CW transmitter is very simple to build. A human operator, listening Morse code and writing down characters as they are sent, is the most efficient data receivers ever devised. Until computers were built to have intuition, there was always a place for Morse code radio communications. Apart from being efficient, as any CW fanatic radio ham will tell you, it is just plain fun to send and receive signals in the Morse code.

Morse code is the form of digital communications.  It is broken down into bits, each having a length of one dot. A dash is 3 bits long. The space between dots and dashes, within the single character, is 1 bit. The space between characters in a word is 3 bits. The space between words is 7 bits. Punctuation marks are sent as characters attached to respective words. Amplitude versus time rendition of Morse word ‘eat’ is given in the figure below.Morse code is a slow way to send and receive data. Human operators use speeds ranging from around 5 words per minute to 40 or 50 wpm.