Emission is the generation by a radio transmitting station of a flow of energy in the form of radio waves (radio waves are electromagnetic waves with frequencies arbitrarily limited to frequencies below 3000 GHz, propagating in space without an artificial waveguide).
A set of characteristics of an emission, designated by established conventional symbols, is called an emission class. In general, an emission class is described by three symbols.
The first symbol (a letter of the Latin alphabet) indicates the type of modulation of the main radio frequency carrier,
the second symbol (a digit) — the nature of the signal modulating the main carrier, and
the third symbol (a letter of the Latin alphabet) — the type of information being transmitted.
Below are the main designations of the symbols describing the emission class.
1. First symbol — type of modulation of the main carrier:
1.1. Emissions in which the main carrier is amplitude modulated (amplitude modulation):
A — double-sideband;H — single-sideband with full carrier;
R — single-sideband with reduced carrier;
J — single-sideband with suppressed carrier;
1.2. Emissions in which the main carrier has angle modulation:
F — frequency modulation;G — phase modulation;
2. Second symbol — nature of the signal(s) modulating the main carrier:
0 — no modulating signal;1 — single channel containing quantized or digital information without the use of a modulating subcarrier;
2 — single channel containing quantized or digital information with the use of a modulating subcarrier;
3 — single channel with analog information.
3. Third symbol — type of information being transmitted:
N — no information transmitted;A — telegraphy for aural reception;
B — telegraphy for automatic reception;
C — facsimile;
E — telephony.
List of emission classes commonly used in maritime radio communication:
A3E — double-sideband telephony (broadcasting);J3E — single-sideband telephony with suppressed carrier;
H3E — single-sideband telephony with full carrier (permitted for use only at 2182 kHz);
F3E — telephony with frequency modulation;
G3E — telephony with phase modulation;
G2B — phase modulation; single channel containing discrete or digital information with the use of a modulating subcarrier;
F1B — frequency-shift telegraphy;
J2B — printing telegraphy using amplitude modulation and frequency-shift keyed subcarrier, transmission in one sideband, suppressed carrier;
A1A — continuous wave telegraphy, Morse code;
A2A — telegraphy with amplitude manipulation of a tone-modulated carrier, Morse code;
F1C — facsimile with direct frequency modulation of the carrier, black-and-white;
F3C — analog facsimile;
P0N — unmodulated pulse emission.
Detailed information on emission classes is provided in Article 4 of the Radio Regulations (RR) and Appendix 6 to the RR.
Unofficial designations of emission classes found in documentation:
F1B — TLX, J3E — SSB, A3E — AM, A1A — CW, A2A — MCW.
After the three main symbols that characterize the emission class, two additional optional characteristics may be used:
* fourth designation (letter) — detailed data on the signal(s);
* fifth designation (letter) — nature of multiplexing.
For the complete designation of emissions, before the emission class designation using four characters, it is possible to indicate the necessary emission bandwidth.
Necessary bandwidth is the bandwidth sufficient, for a given emission class, to ensure the transmission of messages at the required speed and quality under specified conditions. The values of the necessary bandwidth for various emission classes are as follows:
J3E — 2.7 kHz (commercial quality)
H3E — 3.0 kHz (commercial quality)
A3E — 6.0 kHz (commercial quality)
J2B — 304 Hz (at 100 baud)
F1B — 304 Hz (at 100 baud)
F3E — 16 kHz (commercial quality)
F1C, F3C — 1.98 kHz (at 1100 black and white elementary picture elements per second).
Examples of bandwidth designation:
304H — 304 Hz2K70 — 2.7 kHz
16K0 — 16 kHz.
In amateur radio practice, the following types of modulation designations for radio signals are used:
Analog telephonyAM — amplitude modulation
SSB — single-sideband modulation
LSB — Lower SideBand — lower sideband modulation
USB — Upper SideBand — upper sideband modulation
FM — frequency modulation
WFM — wide frequency modulation (frequency deviation = 50 kHz or more)
NFM — narrow frequency modulation (frequency deviation = 6.25–25 kHz)
PM — phase modulation
CW — Continuous Wave — amplitude manipulation of a continuous wave, or in other words, radiotelegraphy
Related articles: Polar modulation, Pilot-tone modulation, GMSK modulation, FM, FDMA, TDMA, dPMR, FM frequencies of Moscow.