This disclosure provides several mechanisms for adapting transmit power spectral density (PSD). A communications device may adapt the power spectrum utilized at the transmitter based, at least in part, on the channel conditions or PSD constraints associated with the communications medium between the transmitter and a receiver device. Additionally, the transmit PSD may be adapted based, at least in part, on a total power capability associated with a transmitter. Power is allocated to improve throughput and utilization of the communications channel. A transmission profile may be selected based, at least in part, on the notch depth. The transmission profile may be associated with symbol timing parameters. The communications device may maintain a plurality of selectable pulse shapes that are optimized for different notch depths.