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What Is a Frequency Receiver?

A frequency receiver is a device that receives wave signals to be converted into audio information. The most common kind of frequency receiver is a radio receiver. Radio receivers use electronic filters to separate different radio signals, then use a series of amplifiers to boost those signals. The first radio receiver was developed in the late 19th century by Russian inventor Alexander Stepanovich Popov. Since then, several kinds of radio receivers have been developed, including low-frequency receivers.

Crystal Sets
- The earliest radio receivers were crystal sets. These used a tuning circuit to detect different frequencies. The tuner then sent an output to a detector, which was formed by placing a thin metal wire on a crystal of a semiconducting mineral. This receiver did not require external power, but because of this, it created no amplification of the signal and suffered from broad selectivity. In other words, the receiver did not precisely detect frequency signals.
Amplification
- The next stage in the development of the radio receiver was to add amplification. These amplified receivers were known as tuned radio frequency receivers and added an amplifier between the antenna and the detector. Adding amplification increased the sensitivity of the receiver over the crystal set but introduced new problems. For example, the gain of the amplifier sometimes increased as the frequency decreased, so the sensitivity of the receiver varied across the frequency range.
The Superheterodyne
- The instability of the frequency range in the tuned radio frequency receivers was solved with the superheterodyne receiver. The basic idea behind the superheterodyne is that all the frequencies coming in to the receiver are converted to a common frequency. This was accomplished by mixing the incoming signal from the antenna with the signal from another radio frequency carrier generated inside a local oscillator. The output is then the difference of the low oscillator signal and the incoming signal, which corrects for the problem of frequency instability across the frequency spectrum.
Advantages and Disadvantages of the Superheterodyne
- The superheterodyne overcomes the problems of both the crystal and tuned radio frequency receivers. This is mostly due to the fact that the superheterodyne does most of the amplification of the signal at an intermediate frequency, which is easier to control, and then mixes that signal to produce other signals. One of the problems with the superheterodyne is that there are two signals that can mix with the local oscillator to produce the desired output. This can add noise to the signal.

Astronomy