An RF switch is used in the signal path to an amplifier, for example between a receiving antenna and an amplifier. The switch is used to alternately connect the amplifier between a normal signal source for the amplifier and a fixed load for calibration. The power difference between the two switch states at the output of the amplifier would then yield a calibrated measurement of a signal value, such as rise over thermal (RoT). The amount of time spent in the calibration position is maintained at a minimized level so as to reduce impact on the normal operation of the amplifier. The invention provides an ability to estimate traffic load in a repeater system based on RoT measurements of repeater reverse-link output power by determining a reverse link gain.