A method and apparatus provide for monitoring radio frequency signals and, in conjunction with the monitoring, determining frequency of a received dominant radio frequency signal. Zero amplitude transitions of the signal are counted in primary and secondary sampling periods to determine frequency and frequency stability. The method and apparatus can be used to tune to radio frequency signals having frequencies in a list of frequencies to be monitored and detecting signals in the radio frequency spectrum on other frequencies. The monitoring and scanning may occur simultaneously, sequentially, or in any order or sequence. The frequencies of dominant signals received are determined and added to the list for monitoring. The receiver may be tuned to a frequency determined immediately upon determination of the frequency determined, after storage of the frequency determined, only after a signal on the currently monitored frequency terminates, or upon other conditions. A user of the apparatus can build a list of frequencies to be monitored automatically without sophisticated knowledge or equipment.