Microbit RRC-1258 MkII(s) Manual de usuario descargar pdf (Pagina 4)

Computers in Amateur Radio

With Morse, the dots, dashes and spaces are all intended to vary

in proportion to one another, as transmission speed varies. Depending

on the speed of transmission, it may sound like a heterodyne (steady

whistle) that is switched on and off. As Fig 2.1 shows, a dash (usually

pronounced ‘dah’) should be three times the length of a dot (pro-

nounced ‘dit’). The space between the letters of a word should be the

same length as a ‘dah’, i.e. three times the length of a ‘dit’ and the

space between words should be seven times the length of a ‘dit’.

Depending on its use and the ability of individual operators, Morse

may be sent at widely differing speeds. On VLF it may be sent extremely

slowly. This is known as QRSs operation, where a ‘dit’ may be many

seconds long. Such slow Morse would be sent by computer, because

manual operation would be too tedious. At the receive end, it would also

be detected and displayed on a computer. This is because at extremely

slow speeds a computer running a Fast Fourier Transform program can

detect and display a signal that is not audible to the human ear.

The speeds that are commonly sent and copied manually by an

operator range from about 5-40 words per minute, although speeds in

the 20s are the most common.

Prior to the development of modern datamodes, looped record-

ings of high-speed Morse (often at 80 words per minute) used to be

employed by Meteor Scatter enthusiasts. Whilst incomprehensible to

the human ear, repetitive high speed Morse messages sound slightly

rhythmic. On receive, fragments of transmission (for that is all that are

typically received in a meteor scatter contact) would be recorded on

tape and then played back at slow speed, for the receiving operator to

copy by ear.

Morse is normally transmitted by on/off keying (Amplitude Shift

Keying), although many beacon stations use Frequency Shift Keying.

Although not often referred to in such terms, Morse code is the Interna-

tional Telegraphic Alphabet No.1.

Baudot (RTTY)

The so-called International Telegraphic Alphabet No.2 was developed for

numerous reasons, not the least of which is that Morse is not easy to

Fig 2.1: An

example of two

words sent in

Morse, with

vertical lines to

show the official

timing and

spacing.

1 2 3 4 5 6 7 8 9 ... 29 30

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