The telegraphic code used for amateur radio telegraphic communication is the International Morse Code consisting of dot (.) and dashes (-). In Morse Code a dot (.) is made by pressing the telegraph key down and allowing it to spring back up again rapidly; and for making a dash (-), the key is held down for a bit longer period. It is said that a dash(-) unit is three time longer than a dot(.) unit. The Morse Code in fact consists of combinations of aurally distinguishable tones. A tone produced for short duration is a dot tone and a tone three times longer than this tone is a dash tone.
To practice Morse Code sending, a novice can use a small device called the ‘Code Practice Oscillator’ (CPO). This is a small electronic circuit capable of generating a sinusoidal audio tone when a key (or switch) is made ‘on’ or ‘off’ manually. It is advisable not to start practice sending the Morse code until the novice is proficient in receiving Morse code. For receiving practice, you have to rely on a ham radio operator who can send/generate Morse code using a CPO or you can try to find out Morse Code transmissions over your radio receiver. Morse code practice cassettes and multimedia computer software are nowadays available. Mere gaining confidence in sending does not qualify you to be an expert receiver! In fact you may not be able to receive a single letter in Morse code even if you gained a sending proficiency of 12 words Per Minute (WPM)! Remembering the Morse codes is an art by itself. It involves a rhythmic response in your mind. Try to remember the combination of dot (.) and dashes (-) by their sound and not as a group of printed symbols. For this purpose, a dot (.) is referred to as a ‘di’ and a dash (-) as a ‘dah’. A ‘di’ coming at the end of the combination is pronounced as ‘dit’
The letter ‘R’ is represented by ‘. – .’ (di dah dit) in Morse code. The time taken to produce the sound equivalent to one ‘di’ or ‘dit’ (dot) is taken as unit time and called a dot unit. A ‘dah’ is approximately of three dot units length and the space between two sound elements of a letter is one dot unit, i.e. silence period is one dot unit. The space between two letters or characters is equal to three dot units. The space between two words is equal to five dot units. The word ‘cat’ can be represented as -.-. .- – (dah di dah dit di dah dah)
The minimum speed to qualify for a Grade II licence is 5 words per minute (5 wpm). 5 letters/characters constitute a word. A message containing 125 letters when sent in 5 minutes or when received in 5 minutes makes your speed 5 wpm.
125/5=25 words in 5 minute; i.e. 5 words per minute.
In fact Morse code devised by Samuel F.B. Morse (1791-1872) is a primitive type of digital communication which still works efficiently in this era of microprocessors and computers. In a computer, all information are processed or stored in binary digits, i.e. 0 and 1s. A zero (0) means that the switch is off and a one (1) makes it on. One interesting fact is that any type of information can be converted to binary digits and later on the information stored in the form of binary digits can be decyphered (decoded).
In the Morse Code system, the encoding is done by ‘short’ and ‘long’ duration of flow of current through a circuit. This method of representing and manipulating information in electrical form is known as digital approach, because the encoded information may be visualized as a series of numerical digits. The modern day computer to computer digital communication (which is automated) can be visualised as an extension of the communication system that started with the hand key operated telegraphic communication (which is manual) back in 1837. The computer can sense the ‘long’ and ‘short’ pulses and decipher them automatically. But a ham receiving Morse code deciphers the message by listening to the ‘short’ and ‘long’ tones. Though the modern day computer communication has its roots in Morse code communication, yet it has been observed that the allocation of Morse codes to the characters has been done in a haphazard manner. It is believed that Samuel F.B. Morse did not visualised his code as a binary sequence. They also believe that Morse did not heard of his now celebrated compatriot George Boole (1854) and his famous work on binary algebra going by his name!
Morse code is also called CW, i.e. Continuous Wave, in the sense that a constant amplitude interrupted radio frequency wave is transmitted; interruption being made in conformity with the code.
The electrical telephone and telegraph are very simple examples which illustrates the difference between the analog and digital methods. In the telephone, the information is transmitted from one end to the other via a current which varies continuously as direct equivalent of sound waves striking the microphone-the analog approach. In the telegraph, the information is encoded (cyphered) and sent as a sequence of current/no current pulses illustrating the digital approach.
Despite the capability of voice communication, Morse code is still in use. One important reason is that a vast group of the radio amateurs still adore Morse code. A ham radio operator employing digital communication techniques (like Packet Radio, Radio Tele Typing-RTTY or Amateur Tele-printing Over Radio-AMTOR) in his ham radio operation treats Morse code with much the same affection he has for those modern innovations. A ham radio operator wearing his headphone and the Morse Key in hand can send message silently without disturbing family members who are in sleep!
Another reason is that short wave radio telephone (voice) signals often suffer very rapid and deep fading; two frequencies separated by only a few hertz, fade at different times. To overcome this, modulated code tones are transmitted. The situation is now that under severe conditions of fading, the carrier frequency may fade out completely but one or the other side band may remain strong as a result a continuously readable signal is received. This is the reason that we hear a band full of exotic sounding CW callsigns at any time of day or night. When the a band appears to be dead, and we can barely copy phone signals, the band remains alive with many CW signals.
(i) The answer is that to communicate human speech, a wider bandwidth is required than that of the CW signal. With a smaller bandwidth the ‘signal to noise ratio’ of the receiver is significantly improved, and the threshold at which signals can still be received above the noise level is therefore extended.
(ii) Also, it is possible for the human ear to be able to resolve CW signals which are only marginally above the noise level, whereas SSB signals of the same signal level could not be copied. It has been suggested that CW has an advantage of approximately 20dB over SSB signals. A narrow bandpass filter improves the CW reception.
Many newcomers seek exemption from ‘tiresome’ Morse test for Short wave operation. This is unfortunate as the Morse code is the key to enter into the world of ham radio with little monetary investment. A novice can assemble a simple Morse code transmitter with lesser technical hurdles than that of a SSB Voice transmitter. Morse code can be learnt easily if we use certain techniques to remember the codes. Learning the Morse code is also a personal venture embarked upon by alone.
Almost all the letters/characters and puncuation marks can be arranged in certain groups which can used to show the resemblance between/among the combination of dot and dashes. For example the letter ‘A’ (. _ ) is the opposite of ‘N’ ( _ . ) in Morse code. Similarly, the letters A, U, V and the character 4 can be made into a group which shows a definite sequence. Given below is a table of such combinations.
EISH TMO AN DU WG BV PX
After remembering the Morse code combination for the EISH combination, the following words can be formed to be sent for receiving practice.
IS HIS SHE
In a similar way, once the novice is able to remember the Morse code combinations for the rest of the combinations shown above, the number of words to be sent can be increased accordingly as shown below.
THIS TOM SOME IT MISS THE
MAN NAME TEN NET HAM
DATE MAD SAD SUN
WHAT WISH SAW WET WASH GONE GOT HUG
BOSS TOMB BOMB HAVE VOTE
PET POT SHOP TAX XEROX
A.G. Reinhold (k2pnk) has devised an innovative method of remembering the Morse Codes by the picturisation of the ‘dot’ and ‘dash’ combinations upon each alphabets.