Definition
An electronic device that allows a single antenna to be shared between a transmitter and a receiver, automatically switching the antenna connection so that transmitted signals go out and received signals come in without the two interfering with each other.
Plain English
A small device that lets one antenna do two jobs — sending and receiving — without the sending side overloading or damaging the receiving side.
Context Anchor
Seen in aircraft radio, radar, transponder, and avionics maintenance discussions when one antenna is shared by sending and receiving equipment.
Derivation
From Latin 'duplex' meaning 'twofold' or 'double.' A duplexer handles two functions (transmit and receive) on one shared line, which is exactly what the name suggests.
Why Pilots Care
Allows efficient use of limited antenna space on the aircraft while protecting the receiver during transmission.
Analogy
Like a traffic light that keeps outgoing and incoming vehicles from colliding on a single-lane road.
Example Sentence 1
The transponder's antenna duplexer routes outgoing replies to the antenna and channels incoming interrogations to the receiver.
Example Sentence 2
A faulty antenna duplexer can cause the transmitter signal to overload the receiver.