Modulation classification

AM modulation

This page contains an abstract of the modulation classification according to the ITU standard.

The classification is done with a three-symbol code: the first symbol (which is usually a letter) describes the modulation of the main carrier, the second symbol (which is usually a digit) describes the signal that modulates the main carrier and the third symbol (which is usually a letter) describes the transmitted information.

Extra modulations only used for a short amount of time (for example for sending the call-ID) are often not taken into account if the main bandwidth is not increased.

First symbol: modulation of the main carrier Second symbol: type of signal(s) modulating the main carrier Third symbol: type of transmitted information
N Unmodulated carrier
Amplitude modulation
A Double sideband amplitude modulated carrier.
H Single sideband, full carrier
R Single sideband, reduced (or variable) carrier.
J Single sideband, suppressed carrier
B Independent sidebands
C Vestigial sideband
Angular modulation
F Frequency modulation
G Phase modulation
Pulse modulation
D Amplitude and phase modulation
P Unmodulated pulse modulation
K Pulse amplitude modulation
L Pulse width/length modulation
M Pulse position/phase modulation
Q Phase modulation during pulses
V Other pulse modulations
Other modulations
W Other combinations of amplitude, phase and pulse modulation
X Other modulations
0 No modulation signal
1 One digital channel, no subcarrier
2 One digital channel, with subcarrier
3 One analog channel
7 Two or more digital channels
8 Two or more analog channels
9 Compound system with one or more digital channels and one or more analog channels
X Other signals
N No information
A Telegraph - manual decoding
B Telegraph - automatic decoding
C Fax
D Data transmission, remote control
E Telephone, audio
F Television, video
W Combination of the above
X Other information


N0N Unmodulated test signal:
A1A Amateur radio CW transmission:
A3E AM broadcast station:
C3F Terrestrial TV (video only):
J3E Amateur radio SSB transmission:
F3E FM broadcast station:
F3F Analog satellite TV (video only):

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, Section 53 et appendice 2.