The TTU Radiocommunication Assembly considering: a) that the concept of “necessary bandwidth” defined in No.146 (S1.152) of the Radio Regulations, is useful for specifying the spectral properties of a given emission, or class of emission, in the simplest possible manner;b) that with regard to the efficient use of the radio-frequency (RF) spectrum, necessary bandwidths for individual classes of emission must be known, that in some cases the formulae listed in Recommendation ITU-R SM. 1138 can only be used as a guide and that the necessary bandwidth for certain classes of emissions is to be evaluated corresponding to a specified transmission standard and required quality; c) that changes in technology have resulted in additions and variations in the modulations used for radiocommunication; d) that the numerical parameters used in the necessary bandwidth formulae may change with time due to changes in signal characteristics (e.g. average talker level).