When several communication systems share a particular frequency band, each of the systems operates subject to the interference generated by the others. Within this scenario, the importance of an accurate assessment of the effects of interference is increased. Given the complexity of the problem, the evaluation of interference is usually done by considering several worst-case situations. These worst-case situations include, for example, the hypothesis that degradation due to rain affects only the victim link and do not affect the interfering links, the hypothesis that the earth stations involved are located at the most unfavorable (in terms of interference) spots in their service area and the use of reference patterns for the radiation patterns of the antennas. obviously, these assumptions imply a conservative calculation of interference in which the obtained interference levels are higher than their actual levels. In this work, as an alternative to the use of envelopes, the earth station sidelobe antenna gains are modeled as random variables. In this case, the resulting carrier to interference ratio is also a random variable. The statistical behavior of the carrier to interference ratio is then evaluated for two different modelings of the antenna sidelobe gains: as exponential distributed random variables and as gamma distributed random variables. The results are compared to those obtained when an envelope is used to characterize the antenna radiation patterns.