The mathematical representation for the variation of levels with small occurrence rate in radio noise

The authors' studies on radio noise in metropolitan areas has been continued, focusing on the statistical features. Recently radio noise measurement in the VHF band was carried out at a point beside a road with busy traffic, using newly developed APD measuring equipment and a spectrum analyzer. The obtained results show the time dependent variation of the statistical properties of the noise. This paper describes the mathematical representation of the variation of higher levels (the small occurrence rate part) of the radio noise. The statistical character of the variation would be important for the estimation of the EM environments.