📡 Receiver (RX)
The onboard unit that receives the transmitter's signal and passes it to the ESC, servos and any other channels.
What it actually does
The receiver is the small unit in the model that listens to your transmitter and passes the instructions to the ESC and servos. It is doing the job that everything else depends on, which is why its placement and its aerials matter more than its size suggests.
In practice
Receivers are described by channel count and protocol, and increasingly output a single digital bus such as SBUS or CRSF instead of separate wires per channel. Many also send telemetry back — pack voltage, temperature, signal strength.
Worth knowing
Aerial placement is the thing people get wrong. Keep aerials away from carbon fibre, metal and the main power wires, keep them straight, and where there are two, position them at right angles to each other.