1.8 Out-of-band spectrum If frequency is plotted as the abscissa in logarithmic units and if the power densities are plotted as ordinates (dB), the curve representing the out-of-band spectrum should lie below two straight lines of constant slope in decibels per octave, starting from the two points situated at the frequencies limiting the necessary bandwidth, and finishing at the level 60 dB. Thereafter, the same curve – should lie below the level 60 dB. The starting ordinates of the two straight lines and their slopes – are given in Table 4, as a function of the modulation index, m. TABLE 4 Modulation index Starting ordinates Slope (dB) (dB/octave) 1.5 6 13 1.8 m  –15  m 6 8 19 0.8 m  –18  m 8 20 19 0.8 m  –20  m The reference 0 dB, corresponds to the mean power of the emission. The permissible amounts of out-of-band power, above and below the frequency limits of the necessary bandwidth, are each approximately 0.5% of the total mean power radiated. The curve representing the out-of-band spectrum for modulation indexes 0.5 1.5 should lie m below the points with the coordinates given in Table 5. 5 Formula for calculating at levels (dB) Bx X –20 –30 –40 –50 –60 3 4.1 5.8 8.1 11 : modulation index m : modulation rate. B For each of the limiting spectrum curve, the abscissa is the relative bandwidth /2 and the Bx B, ordinate is the relative level The reference level 0 dB is the level of the unmodulated carrier. X. 2 Frequency-modulated emissions for sound broadcasting and radiocommunications 2.1 Class of emission F3E, monophonic sound broadcasting 2.1.1 Necessary bandwidth The necessary bandwidth can be calculated by the formula, provided in Recommendation ITUR SM.1138: (12) 2 2 Bn M D K where: : necessary bandwidth Bn : highest modulation frequency M : maximum deviation of the RF carrier D : factor, equals 1 if the condition  is met. K D
1.8 Out-of-band spectrum If frequency is plotted as the abscissa in logarithmic units and if the power densities are plotted as ordinates (dB), the curve representing the out-of-band spectrum should lie below two straight lines of constant slope in decibels per octave, starting from the two points situated at the frequencies limiting the necessary bandwidth, and finishing at the level – 60 dB. Thereafter, the same curve should lie below the level – 60 dB. The starting ordinates of the two straight lines and their slopes are given in Table 4, as a function of the modulation index, m. TABLE 4 Modulation index Starting ordinates (dB) Slope (dB/octave) 1.5 m  6 –15 13  1.8 m 6 m  8 –18 19  0.8 m 8 m  20 –20 19  0.8 m The reference 0 dB, corresponds to the mean power of the emission. The permissible amounts of out-of-band power, above and below the frequency limits of the necessary bandwidth, are each approximately 0.5% of the total mean power radiated. The curve representing the out-of-band spectrum for modulation indexes 0.5 m 1.5 should lie below the points with the coordinates given in Table 5. 5 Formula for calculating Bx at levels X (dB) –20 –30 –40 –50 –60 3 4.1 5.8 8.1 11 m : modulation index B : modulation rate. For each of the limiting spectrum curve, the abscissa is the relative bandwidth Bx /2 B, and the ordinate is the relative level X. The reference level 0 dB is the level of the unmodulated carrier. 2 Frequency-modulated emissions for sound broadcasting and radiocommunications 2.1 Class of emission F3E, monophonic sound broadcasting 2.1.1 Necessary bandwidth The necessary bandwidth can be calculated by the formula, provided in Recommendation ITUR SM.1138: Bn 2 M 2 D K (12) where: Bn : necessary bandwidth M : highest modulation frequency D : maximum deviation of the RF carrier K : factor, equals 1 if the condition D  is met.
R-REC-SM.328-11-200605-I!!MSW-E.docx