RADAR, short for Radio Detection And Ranging, uses rotating antennas to emit radio pulses that echo off objects. The time delay between emission and return determines range, with 6.17 µs per nautical mile. Primary radar displays both permanent echoes (mountains, buildings) and moving targets; a moving‑target indicator removes stationary clutter but can miss aircraft at a “blind speed.”

Coverage depends on transmitter power and atmospheric conditions, and radar operates across six frequency bands (P, L, S, C, X, K). Weather radar systems combine a transmitter/receiver, phased‑array antenna, a cathode‑ray indicator, offering ground‑mapping. Transponders (Mode A/C/S) and TCAS provide identification, altitude, and collision‑avoidance data.