Dual-band frequency diversity seems to be an effective fade countermeasure to rain-induced attenuation in satellite communications above 20 GHz. This method, particularly suited for satellites operating in two frequency bands, typically K/sub a/ band and C or K/sub u/ band, achieves very low levels of outage probability especially where the rain fades are severe. A theoretical analysis of a frequency diversity system is performed to evaluate the amount of reserve capacity needed to counteract fading in a satellite network. The problems that arise in implementing adaptive fade countermeasures because of the dynamic characteristics of fading are discussed, and the results of the simulations performed using the attenuation time series at 11.6 GHz, measured with the Sirio satellite throughout four years, are presented.< >