Definition
The specific radio frequency assigned to the air traffic controller responsible for a defined block of airspace (a sector) within a larger ATC facility such as an Air Route Traffic Control Center (ARTCC) or TRACON. Each sector handles traffic in its own geographic and altitude boundaries, and pilots are handed off from one sector frequency to the next as they progress along their route.
Plain English
The radio channel for the controller who is currently watching your slice of the sky. As you fly across the country, you get passed from one controller's frequency to the next, and each one is a sector frequency.
Context Anchor
You may see or hear sector frequencies on instrument charts, during air traffic control handoffs, or when contacting the next controller in flight.
Derivation
Sector' comes from the Latin 'sectus,' meaning 'cut' or 'divided.' ATC airspace is literally cut up into pieces, each with its own controller and its own frequency, which is why each piece is called a sector.
Why Pilots Care
Using the correct sector frequency ensures timely receipt of vectors, altitude changes, and traffic information from the responsible controller.
Intuition Check
“Sector frequency” does not mean how often a sector is used. It means the radio channel assigned to the controller for that part of the airspace.
Example Sentence 1
After the handoff, the pilot checked in on the new sector frequency: 'Indianapolis Center, Cessna 12345, level at 8,000.'
Example Sentence 2
On the sector frequency the controller issued a heading to avoid traffic.