Telegraphy

Telegraphy, also known as CW (Continuous Wave), is one of the oldest and most traditional modes of amateur radio. It is based on the transmission of Morse code, represented by short and long tone signals (dots and dashes). This method of communication is simple, efficient and has proved to be extremely robust, especially in difficult conditions.


1. basic principle of telegraphy

  • Morse code: Telegraphy uses Morse code, a system of characters in which each letter, number and special character is represented by a combination of short and long signals (dots and dashes).
  • Continuous wave (CW): During transmission, an unmodulated carrier wave is switched on and off to generate the Morse code characters. There is no modulation of the carrier frequency as in other modes, only the switching on and off of the wave, hence the term "continuous wave".


2. use in amateur radio

  • Long distance communication: CW is particularly effective for long distance communication, especially on the short wave bands. Because of its narrowband nature, CW can penetrate atmospheric interference more easily and has a better range than many other types of modulation.
  • Emergency communications: CW is often used in emergency situations because it is more reliable in extreme conditions such as weak signals and high levels of interference.
  • Contests: Many contests have special categories for CW, where contestants try to make as many contacts as possible in a given time.


3. advantages of telegraphy

  • High efficiency: CW requires a very narrow bandwidth (typically 100 to 150 Hz), which allows more users in the same frequency range and concentrates the power of the signal on a narrow frequency.
  • Robustness: CW is extremely robust to noise, interference and poor propagation conditions. Even with weak signals, CW can often be received and decoded where other modes would fail.
  • Simplicity: The equipment required for CW is relatively simple, making it attractive for home-built radios.


4. Disadvantages of telegraphy

  • Learning effort: Learning Morse code takes practice and patience. Although many radio amateurs find this rewarding, it can be a barrier for newcomers.
  • Slower transmission speed: Compared to digital modulation, CW transmission speed is slower, requiring longer times to exchange messages.


5. technical details

  • Morse key: A simple device originally used to manually switch the carrier wave on and off to produce the dots and dashes. Modern versions such as the electronic key (paddle) and the keyer make Morse code transmission easier and faster.
  • Filtering: Because CW produces a very narrow signal, radios use special CW filters to optimise reception and minimise interference from neighbouring signals.
  • Automatic decoding: While many radio amateurs transmit and receive Morse code manually, there is now software and equipment that can automatically decode and display Morse code (to a limited extent).


6. Historical significance

  • The pioneering era of radio: CW was the first and for a long time the dominant mode of radio communication, especially in maritime, military and commercial radio. It was the main method of transmitting messages over long distances until the middle of the 20th century.
  • Exam requirement: In the past, knowledge of Morse code was a prerequisite for obtaining an amateur radio licence. Although this requirement has been abolished in many countries, CW remains a popular mode of operation.


7. CW in modern amateur radio

  • Despite the availability of modern digital modes, CW remains very popular in amateur radio. Many radio amateurs appreciate the simplicity, efficiency and challenge of Morse code operation.
  • QRP operation: CW is particularly popular with low-power radio amateurs (QRP) because CW allows effective communication at very low power levels (often 5 watts or less).


In summary, telegraphy (CW) is a traditional, efficient and robust mode of operation in amateur radio that is still valued by many radio amateurs around the world. Despite technological advances, the ability to transmit and receive Morse code remains a valuable and widely used skill in amateur radio.