Types of radio emissions

Designation details


The bandwidth (BBBB above) is expressed as four characters: three digits and one letter. The letter occupies the position normally used for a decimal point, and indicates what unit of frequency is used to express the bandwidth. The letter H indicates Hertz, K indicates kiloHertz, M indicates megaHertz, and G indicates gigaHertz. For instance, “500H” means 500 Hz, and “2M50” means 2.5 MHz. The first character must be a digit between 1 and 9; it may not be the digit 0 or a letter.


Type of modulation

Character Description
A Double-sideband amplitude modulation (e.g. AM broadcast radio)
B Independent sideband (two sidebands containing different signals)
C Vestigial sideband (e.g. NTSC)
D Combination of AM and FM or PM
F Frequency modulation (e.g. FM broadcast radio)
G Phase modulation
H Single-sideband with full carrier (e.g. as used by CHU)
J Single-sideband with suppressed carrier (e.g. Shortwave utility and amateur stations)
K Pulse amplitude modulation
L Pulse width modulation (e.g. as used by WWVB)
M Pulse position modulation
N Unmodulated carrier
P Sequence of pulses without modulation
Q Sequence of pulses, phase or frequency modulation within each pulse
R Single-sideband with reduced or variable carrier
V Combination of pulse modulation methods
W Combination of any of the above
X None of the above


Type of modulating signal

Character Description
0 No modulating signal
1 One channel containing digital information, no subcarrier
2 One channel containing digital information, using a subcarrier
3 One channel containing analog information
7 More than one channel containing digital information
8 More than one channel containing analog information
9 Combination of analog and digital channels
X None of the above

Types 4 and 5 were removed from use with the 1982 Radio Regulations. In previous editions, they had indicated facsimile and video, respectively.

Type of transmitted information

Character Description
A Aural telegraphy, intended to be decoded by ear, such as Morse code
B Electronic telegraphy, intended to be decoded by machine (radioteletype and digital modes)
C Facsimile (still images)
D Data transmission, telemetry or telecommand (remote control)
E Telephony (voice or music intended to be listened to by a human)
F Video (television signals)
N No transmitted information
W Combination of any of the above
X None of the above

Details of information

Character Description
A Two-condition code, elements vary in quantity and duration
B Two-condition code, elements fixed in quantity and duration
C Two-condition code, elements fixed in quantity and duration, error-correction included
D Four-condition code, one condition per “signal element”
E Multi-condition code, one condition per “signal element”
F Multi-condition code, one character represented by one or more conditions
G Monophonic broadcast-quality sound
H Stereophonic or quadraphonic broadcast-quality sound
J Commercial-quality sound (non-broadcast)
K Commercial-quality sound—frequency inversion and-or “band-splitting” employed
L Commercial-quality sound, independent FM signals, such as pilot tones, used to control the demodulated signal
M Greyscale images or video
N Full-color images or video
W Combination of two or more of the above
X None of the above



Character Description
C Code-division (excluding spread spectrum)
F Frequency-division
N None used
T Time-division
W Combination of Frequency-division and Time-division
X None of the above


Common examples


A3E or A3E G
Ordinary amplitude modulation used for low frequency and medium frequency AM broadcasting
F8E, F8E H
FM broadcasting for radio transmissions on VHF, and as the audio component of analogue television transmissions. Since there are generally pilot tones (subcarriers) for stereo and RDS the designator ‘8’ is used, to indicate multiple signals.
C3F, C3F N
Analogue PAL, SÉCAM, or NTSC television video signals (formerly type A5C, until 1982)
ATSC digital television, commonly on VHF or UHF
DVB-T, ISDB-T, or DTMB digital television, commonly on VHF or UHF

Two-way radio

AM speech communication – used for aeronautical communications
FM speech communication – often used for marine radio and many other VHF communications
20K0 F3E
Wide FM, 20.0 kHz width, ±5 kHz deviation, still widely used for Ham Radio, NOAA weather radio, marine, and aviation users and land mobile users below 50 MHz [1]
11K2 F3E
Narrow FM, 11.25 kHz bandwidth, ±2.5 kHz deviation – All Part 90 Land Mobile Radio Service (LMRS) users operating above 50 MHz were required to upgrade to narrowband equipment by 2013-01-01. [2][3] [4]
6K00 F3E
Even Narrower FM, future roadmap for Land Mobile Radio Service (LMRS), already required on 700 MHz public safety band
SSB speech communication, used on HF bands by marine, aeronautical and amateur users
SSB with reduced carrier (AME) speech communication, primarily used on HF bands by the military (a.k.a. compatible sideband)

Low-speed data

Continuous, unmodulated carrier, formerly common for radio direction finding (RDF) in marine and aeronautical navigation.
Signalling by keying the carrier directly, a.k.a. Continuous Wave (CW) or On-Off Keying (OOK), currently used in amateur radio. This is often but not necessarily Morse code.
Signalling by transmitting a modulated tone with a carrier, so that it can easily be heard using an ordinary AM receiver. It was formerly widely used for station identification of non-directional beacons, usually but not exclusively Morse code (an example of a modulated continuous wave, as opposed to A1A, above).
Frequency-shift keying (FSK) telegraphy, such as RTTY.[a]
High frequency Radiofax
Data transmission by frequency modulation of a radio frequency carrier with an audio frequency FSK subcarrier. Often called AFSK/FM.
Phase-shift keying such as PSK31 (BPSK31)

There is some overlap in signal types, so a transmission might legitimately be described by two or more designators. In such cases, there is usually a preferred conventional designator.

The designators F1B and F1D should be used for FSK radiotelegraphy and data transmissions, no matter how the radio frequency signal is generated (common examples are Audio FSK used to modulate an SSB transmitter or direct FSK modulation of an FM transmitter via varactor diode). However, occasionally the alternatives J2B and J2D are used to designate FSK signals generated by audio modulation of an SSB transmitter.