Definition
A standard VHF radio frequency used by pilots to transmit to a Flight Service Station (FSS) when communicating through a remote communications outlet co-located with a VOR. The pilot transmits on 122.1 MHz and listens for the FSS reply on the VOR's published voice frequency.
Plain English
A common radio channel pilots use to talk to Flight Service. You speak to them on 122.1, and you hear their answer coming back through the VOR you're tuned to.
Context Anchor
Seen in navigation and communication equipment discussions, on aviation charts, and when contacting Flight Service from the airplane.
Derivation
MHz means megahertz. Mega means million, and hertz is the unit for cycles per second, named after Heinrich Hertz. So 122.1 MHz means a radio signal cycling 122.1 million times each second.
Why Pilots Care
Provides direct access to flight services without using the emergency frequency 121.5.
Intuition Check
122.1 MHz is not a navigation course or a navigation signal. It is a voice radio frequency used for communication when it is published for that purpose.
Example Sentence 1
She tuned the VOR, identified its Morse code, then called Flight Service on 122.1 MHz to open her flight plan.
Example Sentence 2
Checking the sectional, the pilot confirmed 122.1 MHz as the transmit frequency for the nearby remote outlet.