Medium frequency atmospheric radio noise measured during periods in 1980 and 1981, and recorded on digital tape in 100-kHz bandwidth has been analyzed to model effects of bandwidth on the noise envelope voltage deviation parameter (Vd). It has been found that the magnitude of this impulsiveness parameter Vd for a given noise sample increases with increasing bandwidth at a slower rate than predicted by CCIR report 322 (International Radio Consultative Committee, Geneva, 1964). Moreover, the rate (slope) is not constant, but rather becomes steeper as the initial (narrower bandwidth) Vd increases due to the impulsive character of the noise at the time of measurement. A simple model based on multiple regression analysis of the MF data allows estimation of Vd in a new bandwidth from a measured Vde using the equation Vd = Vde + (0.4679 + 0.2111 Vde) log BWR, where BWR is the ratio of the new bandwidth to the measured bandwidth. The reason for the unexpectedly small slope lies in the fact that the average envelope voltage, formerly assumed to be independent of bandwidth, increases with increasing bandwidth, but at a slower rate than the rms envelope voltage. Preliminary analysis of a few HF (4–8 MHz) noise recordings indicates a similar behavior in bandwidth effects on Vd.