Morse code

Amateur Morse Code

International Morse code today is most popular among amateur radio operators, in the mode commonly referred to as “continuous wave” or “CW”. (This name was chosen to distinguish it from the damped wave emissions from spark transmitters, not because the transmission is continuous.) Other keying methods are available in radio telegraphy, such as frequency-shift keying.

The original amateur radio operators used Morse code exclusively since voice-capable radio transmitters did not become commonly available until around 1920. Until 2003, the International Telecommunication Union mandated Morse code proficiency as part of the amateur radio licensing procedure worldwide. However, the World Radiocommunication Conference of 2003 made the Morse code requirement for amateur radio licensing optional. Many countries subsequently removed the Morse requirement from their licence requirements.

Until 1991, a demonstration of the ability to send and receive Morse code at a minimum of five words per minute (wpm) was required to receive an amateur radio license for use in the United States from the Federal Communications Commission. Demonstration of this ability was still required for the privilege to use the HF bands. Until 2000, proficiency at the 20 wpm level was required to receive the highest level of amateur license (Amateur Extra Class); effective April 15, 2000, the FCC reduced the Extra Class requirement to five wpm. Finally, effective on February 23, 2007, the FCC eliminated the Morse code proficiency requirements from all amateur radio licenses.

While voice and data transmissions are limited to specific amateur radio bands under U.S. rules, Morse code is permitted on all amateur bands—LF, MF, HF, VHF, and UHF. In some countries, certain portions of the amateur radio bands are reserved for transmission of Morse code signals only.

Because Morse code transmissions employ an on-off keyed radio signal, it requires less complex transmission equipment than other forms of radio communication. Morse code also requires less signal bandwidth than voice communication, typically 100–150 Hz, compared to the roughly 2,400 Hz used by single-sideband voice, although at a lower data rate.

Morse code is usually received as a high-pitched audio tone, so transmissions are easier to copy than voice through the noise on congested frequencies, and it can be used in very high noise / low signal environments. The fact that the transmitted power is concentrated into a very limited bandwidth makes it possible to use narrow receiver filters, which suppress or eliminate interference on nearby frequencies. The narrow signal bandwidth also takes advantage of the natural aural selectivity of the human brain, further enhancing weak signal readability. This efficiency makes CW extremely useful for DX (distance) transmissions, as well as for low-power transmissions (commonly called “QRP operation“, from the Q-code for “reduce power”). There are several amateur clubs that require solid high speed copy, the highest of these has a standard of 60 WPM. The American Radio Relay League offers a code proficiency certification program that starts at 10 wpm.

The relatively limited speed at which Morse code can be sent led to the development of an extensive number of abbreviations to speed communication. These include prosigns, Q codes, and a set of Morse code abbreviations for typical message components. For example, CQ is broadcast to be interpreted as “seek you” (I’d like to converse with anyone who can hear my signal). OM (old man), YL (young lady) and XYL (“ex-YL” – wife) are common abbreviations. YL or OM is used by an operator when referring to the other operator, XYL or OM is used by an operator when referring to his or her spouse. QTH is “location” (“My QTH” is “My location”). The use of abbreviations for common terms permits conversation even when the operators speak different languages.

Although the traditional telegraph key (straight key) is still used by some amateurs, the use of mechanical semi-automatic keyers (known as “bugs”) and of fully automatic electronic keyers is prevalent today. Software is also frequently employed to produce and decode Morse code radio signals. The ARRL has a readability standard for robot encoders called ARRL Farnsworth Spacing that is supposed to have higher readability for both robot and human decoders. Some programs like WinMorse have implemented the standard.

Letters

Numbers

Special charcaters

(*) Eight or more dots.

Accented letters

General remarks

It’s common to express duration of Morse signals as a function of the length of a dot according to the following rules:

The length of a dash is three times the length of a dot.
The space between two signs of the same character is equal to the length of one dot.
The space between two characters of the same word is three times the length of a dot.
The space between two words is seven times the length of a dot (or more).

Of course those rules are not strict at all (especially when using a straight key) and some hams prefer using longer dashes of 3.5 or 4 dots long instead of 3.

Code speed

The keying speed is often expressed in words per minute (WPM), and since the length of the letters is not constant the reference word “PARIS” is commonly used:

As shown in the above diagram, considering spaces between letters after the word itself, the word “PARIS” is exactly 50 dots long, and of course is 5 letters long. Therefore a keying speed of 30 WPM (words per minute) will be equivalent to 150 LPM (letters per minute), each dot will be 40 ms long and each dash will be 120 ms long.

In order to have an idea of the speed of the code here are some examples (.wav files) of the word “PARIS” at different speeds:

The word “PARIS” at 5 WPM
The word “PARIS” at 10 WPM
The word “PARIS” at 15 WPM
The word “PARIS” at 20 WPM
The word “PARIS” at 25 WPM
The word “PARIS” at 30 WPM
The word “PARIS” at 35 WPM
The word “PARIS” at 40 WPM
The word “PARIS” at 45 WPM
The word “PARIS” at 50 WPM

Bibliography and further reading

[1]	OFCOM – Office fédéral de la communication. Prescriptions concernant les radioamateurs. Section concessions de radiocommunication, Rue de l’Avenir 44, CH-2503 Bienne, 2001, Appendice 5.
[2]	Carlo Amorati I4ALU. Manuale di radiotelegrafia. C&C – Edizioni Radioelettroniche, 1995.
[3]	The ARRL Handbook for Radio Communications 2002, Seventy-ninth edition. American Radio Relay League, 2001, Page 12.12.
[4]	Wikipedia

A		(dit daah)
B		(daah dit dit dit)
C		(daah dit daah dit)
D		(daah dit dit)
E		(dit)
F		(dit dit daah dit)
G		(daah daah dit)
H		(dit dit dit dit)
I		(dit dit)
J		(dit daah daah daah)
K		(daah dit daah)
L		(dit daah dit dit)
M		(daah daah)
N		(daah dit)
O		(daah daah daah)
P		(dit daah daah dit)
Q		(daah daah dit daah)
R		(dit daah dit)
S		(dit dit dit)
T		(daah)
U		(dit dit daah)
V		(dit dit dit daah)
W		(dit daah daah)
X		(daah dit dit daah)
Y		(daah dit daah daah)
Z		(daah daah dit dit)

1	(dit daah daah daah daah)	Sometimes abbreviated with A
2	(dit dit daah daah daah)	Sometimes abbreviated with U
3	(dit dit dit daah daah)	Sometimes abbreviated with V
4	(dit dit dit dit daah)
5	(dit dit dit dit dit)
6	(daah dit dit dit dit)
7	(daah daah dit dit dit)	Sometimes abbreviated with B
8	(daah daah daah dit dit)	Sometimes abbreviated with D
9	(daah daah daah daah dit)	Sometimes abbreviated with N
0	(daah daah daah daah daah)	Sometimes abbreviated with T

.	Period		(dit daah dit daah dit daah)
,	Comma		(daah daah dit dit daah daah)
:	Colon		(daah daah daah dit dit dit)
?	Question mark		(dit dit daah daah dit dit)
‘	Quote		(dit daah daah daah daah dit)
–	Hyphen or minus		(daah dit dit dit dit daah)
/	Slash		(daah dit dit daah dit)
(	Left bracket		(daah dit daah daah dit)
)	Right bracket		(daah dit daah daah dit daah)
“	Double quotes		(dit daah dit dit daah dit)
=	Equals		(daah dit dit dit daah)
+	Plus or end of message		(dit daah dit daah dit)
×	Cross		(daah dit dit daah)
SN	Acknowledgment		(dit dit dit daah dit)
K	Transmission request		(daah dit daah)
AS	Wait		(dit daah dit dit dit)
SK	End of transmission		(dit dit dit daah dit daah)
KA	Start of transmission		(daah dit daah dit daah)
	Error	(*)	(dit dit dit dit dit dit dit dit)

è		(dit dit daah dit dit)
à		(dit daah daah dit daah)
ä		(dit daah dit daah)
ö		(daah daah daah dit)
ü		(dit dit daah daah)
ch		(daah daah daah daah)