In one embodiment, a transmitter circuit is provided for transmission of data over power distribution lines using any one of a plurality of carrier frequencies. A data signal generation circuit is configured to encode data bits using a selected carrier frequency. A signal strength module adjusts the signal strength of the data signal according to a signal strength setting, to produce an amplified data signal. A coupling circuit communicates, using a coupling capacitor, the amplified data signal. A current sensing circuit senses current provided to the power distribution lines as a function of degradation of the coupling capacitor. A signal level control circuit adjusts a signal strength setting of the signal strength module for the selected one of the plurality of carrier frequencies as a function of the sensed current and the selected one of the plurality of carrier frequencies.