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The International Telecommunication Union uses an internationally agreed system for classifying radio frequency signals. Each type of radio emission is classified according to its bandwidth, method of modulation, nature of the modulating signal, and type of information transmitted on the carrier signal. It is based on characteristics of the signal, not on the transmitter used.
An emission designation is of the form BBBB 123 45, where BBBB is the bandwidth of the signal, 1 is a letter indicating the type of modulation used, 2 is a digit representing the type of modulating signal, 3 is a letter corresponding to the type of information transmitted, 4 is a letter indicating the practical details of the transmitted information, and 5 is a letter that represents the method of multiplexing. The 4 and 5 fields are optional.
This designation system was agreed at the 1979 World Administrative Radio Conference (WARC 79), and gave rise to the Radio Regulations that came into force on 1st January 1982.
[edit] Designation details
[edit] Bandwidth
The bandwidth is expressed as three digits and a letter that occupies the position normally used for a decimal point. The letter indicates what unit of frequency is used to express the bandwidth. 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.
[edit] Type of modulation
[edit] Type of modulating signal
| 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 analogue information |
| 7 |
More than one channel containing digital information |
| 8 |
More than one channel containing analogue information |
| 9 |
Combination of analogue and digital channels |
| X |
None of the above |
[edit] Type of transmitted information
| N |
No transmitted information |
| 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 |
Telemetry or Telecommand (Remote control or data collection) |
| E |
Telephony (voice or music intended to be listened to by a human) |
| F |
Video (television signals) |
| W |
Combination of any of the above |
| X |
None of the above |
[edit] Details of information
| 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 |
[edit] Multiplexing
[edit] Common and important examples
- N0N
- Continuous, unmodulated carrier - as previously commonly used for radio direction finding (RDF) in marine and aeronautical navigation.
- A1A
- Signalling by keying the carrier directly (aka CW or OOK) - as currently used in amateur radio. This is often but not necessarily Morse code.
- A2A
- Signalling by keying a tone modulated onto a carrier so that it can easily be heard using an ordinary AM receiver - as previously used for station idents of some RDF transmissions. This is usually but not exclusively Morse code. (An example of modulated continuous wave)
- A3E
- AM speech communication - as used for aeronautical VHF communications
- F3E
- FM speech communication - as used for marine and many other VHF communications
- J3E
- SSB speech communication - as used on HF bands by marine, aeronautical and amateur users
- A3E or A3EG
- Normal AM broadcast - as found on public LF and MF bands
- F1B
- FSK telegraphy, such as RTTY. This designator is used no matter how the signal is created (common examples are Audio FSK used to modulate a SSB transmitter or direct FSK modulation of an FM transmitter via varactor diode).
- F8E or F8EH
- Normal FM stereo broadcast - as found on public VHF band, and as the audio component of broadcast television transmissions
- C3F or C3FN
- Broadcast television video signals
Note that there is some overlap, so a signal might legitimately be described by two or more designators. In such cases, there is often a traditionally preferred designator.
[edit] References
