Morse Code Timing: The Rules for Dits, Dahs, and Spaces
Morse code is based entirely on timing. The correct time relationships between the short and long signals (Dits and Dahs), as well as the spaces between them, are crucial for ensuring the code is transmitted correctly and, most importantly, can be received and understood.
The Basic Unit: The Dit
All time units in Morse code are derived from the duration of a Dit (short signal, dot).
- A Dit is the basic unit and lasts for 1 time unit.
The Basic Rules of Timing
The relative lengths of the elements and spaces are internationally standardized:
- Dah (Dash): A Dah is 3 time units long (i.e., 3x the length of a Dit).
- Space between elements: The space within a character (between the Dits and Dahs that compose it) is 1 time unit long (the same length as a Dit).
- Space between characters: The space between two complete letters or numbers is 3 time units long (the same length as a Dah).
- Space between words: The space between two words is 7 time units long.
In Summary:
- Dit:
.(1 unit) - Dah:
-(3 units) - Space within a character:
(1 unit) - Space between characters:
(3 units) - Space between words:
(7 units)
Example: The letter "K" (-.-) would be sent as: Dah (3) + Space (1) + Dit (1) + Space (1) + Dah (3). The total duration of the character "K" would thus be 9 time units. This would be followed by the space to the next character (3 units).
Measuring Speed: WPM (Words Per Minute)
Speed in Morse code is usually specified in WPM (Words Per Minute). To standardize this, the reference words "PARIS" or "CODEX" are used internationally.
- PARIS Standard: The word "PARIS" including the subsequent word space corresponds to a total length of 50 time units (Dits).
- CODEX Standard: The word "CODEX" including the subsequent word space corresponds to a total length of 60 time units (Dits).
The PARIS standard is more common. It allows calculating the Dit duration for a specific speed:
- Dit length (in milliseconds) = 1200 / WPM
Example: At a speed of 20 WPM, a Dit lasts 1200 / 20 = 60 milliseconds. A Dah then lasts 180 ms, a character space 180 ms, and a word space 420 ms.
Farnsworth Timing
Farnsworth Timing is a method often used when learning Morse code. With this method, the characters themselves are sent at the target speed (e.g., 15 or 20 WPM), but the spaces between characters and words are artificially extended.
- Purpose: This gives the learner more time to recognize and process the character just heard, without getting used to a slow rhythm for the characters themselves.
- Example: One might send characters at a speed equivalent to 18 WPM, but extend the spaces so that the effective overall speed is only 10 WPM.
Once character recognition is solid at the target speed, the spaces can be gradually shortened until the normal (standard) timing speed is reached.
Conclusion
Adhering to the correct timing relationships is fundamental for readable Morse code. Whether sent by hand key or electronically, the rhythm is key. Understanding these rules is the first step towards successfully learning and using CW.