Discrete Frequency

A discrete frequency is a radio frequency assigned by ATC specifically to one aircraft or one operation, as opposed to a common frequency shared by all aircraft in an area. Discrete frequencies allow ATC to communicate privately with one aircraft without clogging a common channel or revealing tactical information.

When Discrete Frequencies Are Used

In IFR operations, ATC routinely assigns discrete frequencies as aircraft are handed between sectors. Each sector typically uses its own discrete frequency. During initial IFR clearance delivery, the pilot may receive a discrete departure frequency. In some terminal areas, separate discrete frequencies are assigned for approach and tower.

Guard Frequency

121.5 MHz (VHF guard) is a common emergency frequency monitored by all aircraft and many ATC facilities. It is not a discrete frequency — it is a common monitoring channel. Discrete frequencies are the sector-specific working frequencies listed in the CFS and on en route charts.

Related Terms

See also: Primary Frequency, Broadcast.