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receiverAn electronic device that, in radio astronomy, detects and measures the radio-frequency signals picked up by the antenna of a radio telescope. A receiver that measures the total noise power from the antenna and from itself is called a total-power receiver. This is in distinction to other types that measure, for example, the correlated power in two antennas (see correlation receiver; Dicke-switched receiver; phase-switching interferometer).
Radio-astronomy receivers usually use the superheterodyne technique: the radio-frequency signals at frequency f 1 are combined in a mixer with signals from a local oscillator at frequency f 0 to produce a combination signal whose amplitude faithfully follows that of the radio-frequency signal but whose frequency is f 1 – f 0. This is the intermediate frequency, IF , which is amplified in the IF amplifier and presented to the first detector. The output of the nonlinear detector is a voltage that depends on the input power.
In a total-power receiver the output from the detector becomes the receiver output, having first been smoothed by a low-pass filter to reduce the fluctuations due to the system noise (see sensitivity). In a switching receiver the first detector output is passed to a phase-sensitive detector before smoothing in order to pick out the component at the switching frequency that is buried in the noise. See also line receiver.
a vessel for collecting gas or vapor whose inlet and outlet are of smaller cross section than pipes employed in the whole unit. Receivers also serve to smooth variations in pressure brought about by a pulsating feed and periodic withdrawal. In compressors, receivers are also used to cool the gas and to separate drops of oil and moisture carried in the gas. In steam engines, receivers are thermally insulated pipes that connect the high- and low-pressure cylinders.
receiver(1) A device that accepts signals. Contrast with "transmitter," which sends signals. The term is used generically to refer to "the side being sent to." For example, "by the time the signal gets to the receiver..." refers to whichever hardware device is at the other end of the communication.
(2) A unit of audio or audio/video equipment that serves as the primary control for a stereo or home theater system. See stereo receiver, A/V receiver and head unit.