Definition
An unmanned VHF/UHF transmitter and receiver site used to extend the air-to-ground communications coverage of a Flight Service Station (FSS). The remote site relays radio transmissions between pilots in flight and the controlling FSS specialist, who may be located far from the actual transmitter.
Plain English
A radio relay station out in the field that lets pilots talk to a Flight Service specialist who is sitting somewhere else. The pilot's radio reaches the local antenna, which passes the signal back to the specialist over a landline or network.
Context Anchor
You may encounter this term in FAA radio communication information, especially where voice coverage must reach aircraft that are far from the control facility.
Derivation
"Remote" because the antenna site is physically separated from the specialist working the radio. "Air/Ground" because the link connects aircraft in the air with personnel on the ground.
Why Pilots Care
It extends reliable radio contact with controllers into remote or mountainous areas that lack direct line-of-sight coverage, reducing communication blackouts.
Intuition Check
Remote does not mean you are talking to a different or separate kind of controller. It means the radio equipment used for the call is located away from the main control facility.
Example Sentence 1
He used a Remote Communications Air/Ground Facility to contact Flight Service and close his VFR flight plan after landing at the small airport.
Example Sentence 2
Maintenance crews inspected the Remote Communications Air/Ground Facility to confirm it was still providing clear coverage for low-altitude flights.