Cloud radars typically transmit pulsed signals (in the same way as the MST radar) and determine the range of targets from the delay between the transmission and reception of a pulse. Owing to the relatively high peak transmitted powers (~ 1 kW), they rely on expensive vacuum valves, which are prone to degradation over time scales of 1 - 2 years. An alternative technique is to "chirp" the signal, i.e. to linearly sweep the transmitter frequency, and to determine the range of a target from the frequency difference between the transmitter and receiver signals. Since signals are transmitted for a much longer period than in the case of pulsed radar (there are still gaps between chirps), detectable return signals can be achieved with a much lower peak transmitter power (200 mW in the case of the RAL radar). This means that FMCW radars can be designed around lower-cost and more-reliable solid-state components.