Why should effective radiated power (ERP) be limited to a satellite that uses a linear transponder?

Satellites using linear transponders have a limited amount of available DC power for their transmitters. A linear transponder translates an entire band of signals simultaneously and divides its available downlink power among all the signals present in its passband. If a station uses excessively high effective radiated power (ERP) on the uplink, their signal will dominate the transponder's receiver. The satellite's automatic gain control (AGC) will reduce the overall gain, or the transponder will allocate most of its output power to retransmitting that single loud signal. As a result, the downlink power available for all other users is drastically reduced, effectively drowning out weaker stations. Therefore, operators should use only the minimum power necessary to establish contact.