RECOMMENDATION 638 - TERMS AND DEFINITIONS USED IN FREQUENCY PLANNING FOR SOUND BROADCASTING **
1. Signal-to-interference ratios
2. Specific field strengths
    2.1  Minimum usable field strength (Emin)
    2.2 Usable field strength (Eu)
    2.3 Reference usable field strength (Eref )
3. Coverage area (of a broadcasting transmitter in a given broadcasting band)