In a technique for detecting single or multiple channels in a broadcast RF signal, a receiver determines a constant modulus indication value for each frequency of the receiver's local oscillator, as that oscillator is tuned across a range of possible channel frequencies. The receiver may determine this constant modulus indication value by determining the magnitudes of a constant modulus signal and a noise signal, for a signal output from a digital front end, that signal representing a mixing of the local oscillator frequency signal with the broadcast RF signal and a channelization thereof. As the local oscillator frequency signal is tuned through the range of possible channel frequencies, the receiver evaluates the constant modulus indication value course and or fine frequency increments to determine if the constant modulus indication value at any frequency rises above a threshold value, thereby indicating that the local oscillator frequency signal has locked onto an RF channel in the original RF signal.