The five-step loop
1. The transmitter emits a microsecond-long pulse of radio waves through a directional antenna. 2. The pulse travels outward at the speed of light. 3. When it strikes something with a different electrical conductivity than air — an aircraft, a raindrop, a hillside — a tiny fraction reflects back. 4. The receiver, sharing the same antenna, listens for the echo. 5. The system measures the round-trip time and computes range as (time × speed of light) / 2.
A pulse 1 microsecond long produces a range resolution of about 150 metres. Shorter pulses give finer resolution but less energy, so radars trade pulse width against range using pulse compression — a chirped pulse that is long on transmit and short on receive.
Pulse Repetition Frequency (PRF)
A radar sends pulses many times per second. The PRF sets the maximum unambiguous range: if a pulse comes back after the next one has gone out, the system cannot tell which echo belongs to which pulse. Low PRF (a few hundred Hz) gives long range — useful for air-search radars. High PRF (tens of kilohertz) gives accurate Doppler velocity — useful for fighter intercept radars.
Direction comes from the antenna
Range comes from time. Bearing comes from where the antenna is pointed when the echo arrives. A rotating dish gives a full 360° sweep every few seconds. A phased array steers the beam electronically in microseconds — the entire array stays still and the beam moves through interference patterns between hundreds of small radiators.
Why this shows up in games
Signal//Lock's radar uses exactly this idea. A directional sweep ticks across the screen. When it crosses a signal, the signal becomes 'lockable' for a brief window — the same way a real PPI scope only shows a contact when the antenna is pointed at it. Holding the lock while the sweep moves away is the game's core challenge, and it maps directly onto the real problem an air-defence operator faced in 1942.