An IF, or intermediate frequency, is a transitional radio frequency situated between two other frequencies. It is often created by mixing two frequencies together via a signal enhancement process called heterodyning. An IF signal can be used to move information between frequency channels and to filter out unwanted signal information.
When a group of frequencies is packed too tightly together, a radio may pick up information from several frequencies and transmit sound from more than one station at a time. An IF conversion helps to filter out stray information from neighboring frequencies, allowing for more accurate tuning and improving the quality and strength of the signal.