Chapter 26 - Sending Morse Code

Abstract

This chapter describes the building of an electronic keyer to simplify the task of sending Morse code. A keyer translates contact closures from a paddle into perfectly formed and spaced dots, dashes and spaces. A paddle is nothing more than a pair of single-pole, single throw switches, operated by pressing one lever or the other. Based on the status of the dot and dash levers, the keyer automatically completes the correct length dot or dash, sends alternating dots/dashes, adds the correct end-of-element space, and displays the sent letters on an liquid crystal display (LCD) display. It uses two rotary encoders to select and set important parameters, such as sending speed and the dot/dash ratio. Morse code is comprised not only of dots and dashes but also spaces. The duration of dots, dashes, and spaces are defined with respect to the duration of a single dot. Morse is a variable length code, where the most common letters are represented by the shortest combination of elements. Morse code speed is universally defined in “words per minute” and the standard word “PARIS” is comprised of 50 elements, including inter-character, inter-letter, and inter-word spaces, where an element is equal to one dot length. An algorithm that looks at the status of the opposite paddle lever beginning halfway through the current element is also elaborated in the chapter.