[en] The PEPI rf system will consist of twelve 500-kW klystrons. Each klystron will feed two identical 5-cell cavities via a MAGIC-T power splitter. The rf system will be expanded in PEPII and will consist of twenty-four klystrons and ninety-six 5-cell cavities with each klystron feeding four cavities. Since the performance and stability of the system can be affected by the load admittance as seen by the klystron and the klystron admittance as seen by the beam, the values of the system parameters should be chosen such that the power transfer to the beam is maximized at maximum design operation and the system is stable over all possible operating conditions of the storage ring. The design parameters in the rf system considered in this study are: θ = the phase-shift between the klystron and the cavity including the phase-shift in the MAGIC-T; β/sub c/ = the coupling coefficient between the transmission line and the cavity; /phi/₁ = the phase angle of the beam-loaded cavity admittance Y/sub c/. The relevant parameters which describe the storage ring operation are: E = the beam energy; I/sub B/ = I/sub B/⁺ + I/sub B//sup /minus// the fundamental component of the total /+-/ beam current; V/sub c/ = the fundamental component of the accelerating voltage per cavity. The effects of θ, β/sub c/ and /phi//sub l/ upon the performance of the klystron and the stability of the beam-cavity interaction over a possible range of value of E, I/sub B/ and V/sub c/ have been studied and the results are described in this report. 6 refs., 5 figs