A radiofrequency circuit embedded onboard a satellite, data being transmitted on several channels by radiofrequency signals, includes a channel corresponding to a frequency band, and a succession of gains being able to be associated with a channel so as to generate the radiofrequency signal to be transmitted on the latter. The succession includes at least one variable-gain amplifier, the radiofrequency signals thus generated being multiplexed by a multiplexer composed of bandpass filters. The successions of gains comprise a power load arranged so as to dissipate the power of signals which is reflected by the filters of the multiplexer, said load including means for generating an alarm signal representative of the power level of the reflected signals, the alarm signal being used to control the gain of the variable-gain amplifier. The subject of the invention is also a power load.