THE MORSE CODE
The Amateur Radio Service is the only officially
recognized service that still uses Morse code on a regular basis, although it is
still used by some military and commercial agencies throughout the world and as
a system for indicating the identity of automatic beacons and similar devices.
The use of Morse by Radio
Amateurs should not be seen as the use of an obsolete technology by a group of
individuals who have been left behind by the advance of science. Quite the
reverse, as a skilled operator using Morse code will be able to achieve reliable
contact under incredibly difficult conditions of interference and poor
propagation causing weak and variable signals, which would result in the failure
of automatic systems.
Also, the equipment required does not need to be complicated or expensive, but
the speed of Morse communication is slow and the type of data transmitted is
limited to upper case alpha-numeric text. Furthermore, the system relies
on the human brain for coding and decoding and therefore suffers from the
possibility of errors occurring, particularly when the operator is tired or
stressed. Obviously, this is not the case with machine based systems.
The various former users of Morse from commercial and military agencies have
turned to other systems, as equipment cost is relatively unimportant, whereas
reliability, accuracy, high speed, data volume and content and no necessity to
employ trained telegraphists, is of paramount importance. Also, these
links often employ
satellites, but even the terrestrial links do not suffer from weak signals and
interference, as the optimum frequency and power levels for a particular purpose
can be chosen. Additionally, excellent antenna systems and station
locations can be selected to ensure strong signals. Few, if any, of these
luxuries are available
to the Radio Amateur, who has to rely on his own skill, limited power and
whatever antenna he can erect in his own back yard.
The line telegraph was invented in the USA by Samuel Finley Breese Morse
(1791-1872) but it was Alfred Vail (1807-1859) who actually invented the coding
system that is now known as the Morse code. The Morse telegraph system
using Vail's original code was used extensively on the telegraph circuits of the
American railways. Some code groups were different to those currently forming
the International Morse Code, and thanks are due to Denzil, G3KXF, for providing
the listings of these American landline telegraph code groups which are included
below. It is interesting to note that the Amateur Radio codes "73" (best
wishes) and "88" (love and kisses), are believed to have been first used by
American railway telegraph operators during the nineteenth century and the CW
abbreviation for "and" is "es", which is actually the old American land-line
telegraphy code group for the ampersand (&).
Morse code was also ideal for use with early
radio transmitters before methods of modulating an RF carrier became available
with the invention of the radio valve. Many marine installations employed spark
transmitters which, by their very nature, could not be modulated, but they could
be easily interrupted, or keyed, to form
code groups.
Unlike the Murray Code used by teleprinters,
where the code groups always contain the same number of bits, the Morse code
uses varying length code groups. The letters occurring most frequently in
English are represented by short groups, whereas the lesser used letters are
represented by longer groups. This variable
length makes automatic error detection and correction by electronic means
virtually impossible. There are many computer programmes available to send
and receive Morse code automatically, but these are not error correcting and are
therefore prone to decoding problems if the received signal is suffering from
fading or interference or is badly spaced hand-sent Morse. However, Morse
that is hand-sent by a skilled operator is virtually indistinguishable from
machine sent Morse.
Normal practice is to refer to a Morse "dot" as "di" or "dit", depending on its
position in the group, and a Morse "dash" as "dah". When spoken, these words
give a good impression of what the Morse signal actually sounds like. An example
of actual Morse can be heard by clicking
"sound of Morse". This is an off-air recording of Morse being used by
skilled Amateur Radio operators during a contest.
The normally accepted timings for International Morse Code signals are:
dot
1 time unit
dash
3 time units
space between
elements of a letter 1 time unit
space between
letters of a word 3 time units
space between
words
5 time units
Obviously, the value of "1 time unit" depends on the overall speed of
transmission. Speeds are normally expressed in "words per minute" or "wpm".
As words can vary in length, the word "PARIS" is normally accepted as being the
standard length word used for speed calculation. This means that if the
word "PARIS" were to be sent twenty times in one minute, with spaces between the
words, the transmission speed would be 20wpm. Obviously, if shorter words
were to be sent, but the same element timings were used, the speed would still
be 20wpm but more than twenty words would be sent in one minute. The
original landline Morse code, which is described later, did not specify timings.
The International Morse Code, as defined by the ITU Radio Communication Sector
(ITU-R) Study Group 8, is shown below, together with the Russian Alphabet,
special accented letters used in languages other than English and Russian,
abbreviated codes for numbers and various procedural signals. All
characters in the Morse code are assumed to be upper case. There are no
separate codes for lower case letters.
THE INTERNATIONAL MORSE CODE
A didah .- 1 didahdahdahdah .----
B dahdididit -... 2 dididahdahdah ..---
C dahdidahdit -.-. 3 didididahdah ...--
D dahdidit -.. 4 dididididah ....-
E dit . 5 dididididit .....
F dididahdit ..-. 6 dahdidididit -....
G dahdahdit --. 7 dahdahdididit --...
H didididit .... 8 dahdahdahdidit ---..
I didit .. 9 dahdahdahdahdit ----.
J didahdahdah .--- 0 dahdahdahdahdah -----
K dahdidah -.-
L didahdidit .-.. . didahdidahdidah .-.-.-
M dahdah -- , dahdahdididahdah --..--
N dahdit -. ? dididahdahdidit ..--..
O dahdahdah --- - dahdididididah -....-
P didahdahdit .--. = dahdidididah -...-
Q dahdahdidah --.- : dahdahdahdididit ---...
R didahdit .-. ; dahdidahdidahdit -.-.-.
S dididit ... ( dahdidahdahdit -.--.
T dah - ) dahdidahdahdidah -.--.-
U dididah ..- / dahdididahdit -..-.
V didididah ...- " didahdididahdit .-..-.
W didahdah .-- $ didididahdididah ...-..-
X dahdididah -..- ' didahdahdahdahdit .----.
Y dahdidahdah -.-- ¶ didahdidahdidit .-.-..
Z dahdahdidit --.. _ dididahdahdidah ..--.-
@ didahdahdidahdit .--.-. (Note 1)
! See Note 2 below
+ See Note 3 below
Error didididididididit ........ (Note that this is sometimes abbreviated to three or four dots
sent at a much lower speed than that currently being
used in the message
Notes
1. Originally, there was no code group for the e-mail address "at" sign
(@) in the International Morse Code, but didahdahdidah .--.- (À) was often
used in French speaking countries. However, in December 2003, the
ITU recommended that didahdahdidahdit .--.-. (AC) should be adopted for
international use. With the agreement of all member states, this new code
group has now been added to the official International Morse Code character set.
2. There is no code group for the exclamation mark (!) in the
International Morse Code, but dahdahdahdit ---. (the code originally used over
landlines in the USA and Canada) is sometimes also used over radio links in
those countries. Some years ago, the Heathkit Company were
advocating the use of -.-.-- (KW) for the exclamation
mark.
3. Although not included in the official listings, didahdidahdit .-.-. is
often used to represent the plus sign (+).
4. When sending numbers having integer and fractional parts, the
fractional part is preceded and followed by hyphens. (e.g. 2½ would be
sent as 2-1/2-).
5. Amateur Radio operators often use the letter "R" (didahdit .-.) to
represent a decimal point, but this convention is not generally followed by
other Services.
LETTERS USED IN THE RUSSIAN ALPHABET (CYRILLIC)
А didah
.-
Р didahdit
.-.
Б dahdididit -...
С dididit
...
В didahdah .--
Т dah
-
Г dahdahdit --.
У dididah
..-
Д dahdidit -..
Ф dididahdit
..-.
Е dit
.
Х didididit
....
Ё dit
.
Ц dahdidahdit -.-.
Ж didididah ...-
Ч dahdahdahdit ---.
З dahdahdidit --..
Ш dahdahdahdah ----
И didit
..
Щ dahdahdidah --.-
Й ditdahdahdah .---
Ъ dahdididah
-..-
К dahdidah -.-
Ы dahdidahdah -.--
Л didahdidit .-..
Ь dahdididah
-..-
М dahdah
--
Э dididahdidit ..-..
Н dahdit
-.
Ю dididahdah
..--
О dahdahdah ---
Я didahdidah
.-.-
П didahdahdit .--.
ACCENTED LETTERS USED IN EUROPEAN LANGUAGES OTHER THAN ENGLISH AND RUSSIAN
Ä, Ą
didahdidah .-.-
Ö, Ó dahdahdahdit ---.
Â, À, Á, Å didahdahdidah .--.-
Ñ dadahdidahdah --.--
Ç, Ć dahdidahdidit
-.-.. Ü
dididahdah ..--
É, Ę dididahdidit
..-.. Ż dahdahdidit
--..
È
didahdididah .-..- Ź
dahdahdididah --..-
Ê
dahdididahdit -..-. CH, Ş
dahdahdahdah ----
ACCENTED LETTERS USED IN ESPERANTO
Ĉ
dahdidahdidit -.-..
Ĵ didahdahdahdit .---.
Ĝ
dahdahdidahdit --.-. Ŝ
didididahdit ...-.
Ĥ
dahdidahdahdit -.--. Ŭ
dididahdah ..--
PROCEDURAL SIGNALS
__
Wait (AS) __
didahdididit
.-...
Understood (SN) __
didididahdit
...-.
End of message__(AR)
didahdidahdit .-.-.
End of work (SK) __
didididahdidah ...-.-
Starting signal (KA)
dahdidahdidah -.-.-
Invitation to transmit (K)
dahdidah
-.-
Short pause (for thought?) (II)
didit didit
.. ..
General call to any station (CQ)
dahdidahdit dahdahdidah -.-. --.-
Closing down (CL)
dahdidahdit didahdidit -.-. .-..
The following procedural signals are not used by the Amateur Radio Service:-
_____
Break-in signal (TTTTT) __
dahdahdahdahdah -----
Executive message signal (IX)
dididahdididah ..-..-
Interrogatory signal (INT)__
dididahdidah
..-.-
Emergency silence signal (HM)
dididididahdah ....--
Emergency Distress signal (SOS)
didididahdahdahdididit ...---...
This signal replaced the original distress signal CQD,
which was used in the early years of the 20th century.
___
Relay of distress message (DDD)
dahdididahdididahdidit -..-..-..
An interesting point to note is that reporters, when using the American
land-line telegraph system, were in the habit of sending "30" to indicate the
end of a story. They would have been using the land-line code (see below) where
"3" is ...-. and "0" is ——— (a long dash). Therefore, "30" would be sent
as ...-.——— which becomes
...-.- when sent with standard Morse Code timing, which is the normal
"end of work" signal SK.
ABBREVIATED NUMBERS
These abbreviated numbers are not legal for use
in call signs and should only be used where there is agreement between operators
and when there is no possibility of confusion. Their main use by the
Amateur Service is as a time saver when sending reports during contest operation
or "pile-ups". For obvious reasons,
the most commonly used abbreviated numbers are those for "5" and "9".
1 didah .-
6 dahdidididit -....
2 dididah ..-
7 dahdididit -...
3 didididah ...-
8 dahdidit -..
4 dididididah ....-
9 dahdit -.
5 dit
.
0 dah
-
ORIGINAL AMERICAN LANDLINE MORSE CODE (NOW OBSOLETE)
Note that L is a long dash and T is a short dash,
while C, O, R, Y, Z, :, ;, -, ', /, (, ), " and & are composed of dots and
spaces. Zero (0) is a very long dash and was usually abbreviated to T.
As C comprises I and E it is difficult to see how words such as "FRIED" or
"FRIEND" would, or could, be sent, especially as there is
no specific timing quoted for this code. If you thought that mastering the
normal International Morse Code was difficult, try learning this!!!
A didah
.-
1 didahdahdit
.--.
B dahdididit -...
2 dididahdidit
..-..
C didit dit .. .
3 didididahdit
...-.
D dahdidit -..
4 dididididah
....-
E dit
.
5 dahdahdah
---
F didahdit .-.
6 didididididit
......
G dahdahdit --.
7 dahdahdidi
--..
H didididit ....
8 dahdidididit
-....
I didit
..
9 dahdididah
-..-
J dahdidahdit -.-.
0 daaaah
——— (very long dash)
K dahdidah
-.-
L daah
—— (long dash)
M dahdah
--
. dididahdahdidit
..--..
N dahdit
-.
, didahdidah
.-.-
O dit dit . .
? dahdididahdit
-..-.
P dididididit .....
: dahdidah dit dit -.- . .
Q dididahdit ..-.
; dididit didit
... ..
R dit didit . ..
- didididit didahdidit .... .-..
S dididit ...
! dahdahdahdit
---.
T dah
-
' dididahdit didahdidit ..-. .-..
U dididah ..-
/ dididah dah
..- -
V didididah ...-
( dididididit dahdit ..... -.
W didahdah .--
) dididididit didit didit ..... .. ..
X didahdidit .-..
“ dididahdit dahdit ..-. -.
Y didit didit .. ..
” dididahdit dahditdahdit ..-. -.-.
Z dididit dit ... .
& dit dididit
. ...
US NAVY "MORSE" CODE (NOW OBSOLETE)
According to the 1911 edition of the "Cyclopedia of Applied Electricity", the US Navy once used a rather bizarre coding system for sending messages based on "dots" and "dashes" but having different code groups from normal Morse code. This system used a limited number of code groups and some letters and numbers shared the same group. There were no punctuation signs or procedural signals, apart from "error" and "understand". The message context was supposed to indicate which letter or figure was actually being sent. This could obviously lead to ambiguities and use of this code system was eventually discontinued. A dahdah -- 1 didididit .... B, 0 dahdididah -..- 2 Shared character (see Z) C didahdit .-. 3 didididah ...- D dahdahdah --- 4 Shared character (see F) E didah .- 5 dididahdah ..-- F, 4 dahdahdahdit ---. 6 Shared character (see G) G, 6 dahdahdidit --.. 7 Shared character (see V) H didahdah .-- 8 dahdididit -... I dit . 9 Shared character (see M) J dididahdah ..-- 0 Shared character (see B) K dahdidahdit -.-. L dahdahdit --. M, 9 didahdahdit .--. N didit .. O dahdit -. Error didah didah didah .- .- .- P didahdidah .-.- Understand dahdah dahdah -- -- Q didahdidit .-.. R dahdidit -.. S dahdidah -.- T dah - U dididah ..- V, 7 didahdahdah .--- W dididahdit ..-. X dahdidahdah -.-- Y dididit ... Z, 2 dahdahdahdah ----