The ITU uses an internationally agreed system for classifying radio frequency signals. Each type of radio emission is classified according to a number of factors which describe the characteristics of the signal – not the transmitter used
This classification, referred to as the Emission Designation, has a minimum of 3 characters, showing:
1. Type of Modulation
example: J = Single-sideband, suppressed carrier
example: F = Frequency modulation
2. Nature of modulating signal
example: 1 = One channel containing digital information, no subcarrier
example: 3 = One channel containing analogue information
3. Type of information transmitted
example: D = Data, e.g. RTTY
example: E = Telephony, e.g. voice
For purposes of the exam, these emission designations should be known:
- A1A = CW (Morse, on/off keying of the carrier)
- J3E = SSB (single sideband, suppressed carrier, speech)
- A3E = AM (amplitude modulation, speech)
- F3E = FM (frequency modulation, speech)
- F1B, F2B, J2B = RTTY / AMTOR
- F1D, F2D, J2D = Packet / Data