1. An electronic device that detects and amplifies radio signals captured by an antenna. Receivers used in radio astronomy are generally similar in principle to those used for other purposes, such as a domestic radio, although they are usually cooled to near absolute zero to reduce thermal noise and hence increase their sensitivity. On radio telescopes the incoming signal is mixed with a local oscillator to produce a lower intermediate frequency that suffers lower loss when passing from the telescope to the observing laboratories. This is sometimes termed a superheterodyne receiver. See also Dicke Radiometer.

2. The equipment used to process signals received by a radio telescope. There are three main types: line receivers are used to observe spectral lines, where high stability is required together with the ability to scan in frequency or to observe at several closely spaced frequencies; continuum receivers are used for carrying out radio source surveys at a wide band of frequencies; and timing receivers are used to measure the arrival times of the radio pulses emitted by pulsars. See also Correlation Receiver.