A method and apparatus for controlling a gain of an amplifier of a cable modem operating in a full duplex (FDX) mode. A cable modem includes an amplifier configured to amplify a received signal, a power meter configured to measure a power of the received signal on a plurality of channels, and a control unit configured to estimate a maximum expected power to receive on the plurality of channels based on the measured power and set a gain of the amplifier based on the maximum expected power. The cable modem is configured to operate in a full duplex mode. The channels include a full duplex upstream channel, a full duplex downstream channel, and a legacy downstream channel. The maximum expected power may be estimated via a sounding procedure. A power spectral density may be measured and the maximum expected power may be derived from the power spectral density.