Question T6D02
From subelement T6 - T6D
What is a relay?
Why is this correct?
A relay is an electrically-controlled switch that uses electromagnetic principles to physically open or close contacts. When current flows through the relay's coil, it creates a magnetic field that moves mechanical contacts, making or breaking connections in other circuits. This differs from amplifiers (options B and C) which modify signal strength, and pass transistors (option D) which are solid-state devices without moving parts.
Memory tip
Remember the key distinction: relays have moving mechanical parts that physically connect or disconnect circuits, while electronic components like transistors control current flow without physical movement. Listen for the characteristic 'click' sound when relays operate - that's the contacts moving.
Learn more
In amateur radio stations, relays serve critical functions including antenna switching between different bands, controlling transmit/receive sequencing, and managing high-power amplifier operations. Unlike solid-state switches, relays can handle high voltages and currents while providing complete electrical isolation between control and switched circuits. This isolation prevents ground loops and protects sensitive control circuits from high RF voltages during transmission.
Think about it
Why do you think amateur radio operators often prefer relays over electronic switches for antenna switching, despite relays being slower and having moving parts that can wear out?