An experimental technique for the coherence-time characterization of a mobile radio envelope employing the autocorrelation co-efficient is presented. Field trials at 836 MHz in a suburban area are carried out using a spectrum analyzer as the acquisition apparatus. Autocorrelation coefficients are calculated from the acquired envelopes and the coherence time is calculated for a 0.5 correlation level. Due to the significant variation of the coherence time with the position of the mobile receiver, cumulative distribution functions of the coherence time are calculated in order to interpret the results. The coherence-time parameter is estimated from these cumulative distribution functions by computing the value above which the coherence time stays for 90% of the time. (c) 2006 Wiley Periodicals, Inc.48611371141