A radio receiver for receiving a selected DTV signal that can be a quadrature-amplitude-modulation (QAM) signal or a vestigial sideband (VSB) signal synchrodynes the received signal to baseband and supplies the baseband signal to an adaptive equalizer. The presence of the pilot carrier accompanying a selected VSB DTV signal is detected for automatically switching the radio receiver for operation in a VSB signal reception mode, in which operating mode the adaptive equalizer is conditioned to respond to training signals included in the initial data segment of each data field of the VSB signal. The absence of pilot carrier accompanying a selected QAM DTV signal is detected for automatically switching the radio receiver for operation in a QAM signal reception mode, in which operating mode the adaptive equalizer is conditioned to operate without relying on the training signals included in the VSB signal.