Bandspread

In a radio receiver, a bandspread control is a secondary tuning control that allows accurate tuning of closely spaced frequencies of a radio band. With a main tuning control that covered a wide range of frequencies, for example 10-14 megahertz in a few turns of the tuning knob, a very small motion might chang the tuning by tens of kilohertz and would make accurate tuning to any given frequency difficult. A calibrated bandspread tuning control would allow the main tuning to be set to a predefined spot on the control and the bandspread would allow tuning of a particular frequency within some restricted range of the main tuning control.