23 Facts About Radio receivers

Radio receivers are essential components of all systems that use radio.

However radio receivers are very widely used in other areas of modern technology, in televisions, cell phones, wireless modems, radio clocks and other components of communications, remote control, and wireless networking systems.

Radio receivers are essential components of all systems that use radio.

Besides the broadcast receivers described above, radio receivers are used in a huge variety of electronic systems in modern technology.

Radio receivers receiver is connected to an antenna which converts some of the energy from the incoming radio wave into a tiny radio frequency AC voltage which is applied to the receiver's input.

Practical radio receivers perform three basic functions on the signal from the antenna: filtering, amplification, and demodulation:.

Since it is easy to amplify a signal to any desired degree, the limit to the sensitivity of many modern receivers is not the degree of amplification but random electronic noise present in the circuit, which can drown out a weak radio signal.

Therefore, almost all modern receivers include a feedback control system which monitors the average level of the radio signal at the detector, and adjusts the gain of the amplifiers to give the optimum signal level for demodulation.

Radio receivers waves were first identified in German physicist Heinrich Hertz's 1887 series of experiments to prove James Clerk Maxwell's electromagnetic theory.

Therefore, the first radio receivers did not have to extract an audio signal from the radio wave like modern receivers, but just detected the presence of the radio signal, and produced a sound during the "dots" and "dashes".

The first Radio receivers had no tuned circuit, the detector was connected directly between the antenna and ground.

The form of bandpass filter that was used in the first Radio receivers, which has continued to be used in Radio receivers until recently, was the double-tuned inductively-coupled circuit, or resonant transformer.

Until recently the bandpass filters in the superheterodyne circuit used in all modern Radio receivers were made with resonant transformers, called IF transformers.

The millions of people who purchased or homemade these inexpensive reliable receivers created the mass listening audience for the first radio broadcasts, which began around 1920.

Today these simple radio receivers are constructed by students as educational science projects.

Amplifying vacuum tube used energy from a battery or electrical outlet to increase the power of the radio signal, so vacuum tube receivers could be more sensitive and have a greater reception range than the previous unamplified receivers.

Defect in many early vacuum-tube receivers was that the amplifying stages could oscillate, act as an oscillator, producing unwanted radio frequency alternating currents.

Radio receivers was the first to give a correct explanation of how De Forest's triode tube worked.

Radio receivers invented the feedback oscillator, regenerative receiver, the superregenerative receiver, the superheterodyne receiver, and modern frequency modulation.

Major problem of early TRF receivers was that they were complicated to tune, because each resonant circuit had to be adjusted to the frequency of the station before the radio would work.

In later TRF Radio receivers the tuning capacitors were linked together mechanically on a common shaft so they could be adjusted with one knob, but in early Radio receivers the frequencies of the tuned circuits could not be made to "track" well enough to allow this, and each tuned circuit had its own tuning knob.

Invention of the transistor in 1947 revolutionized radio technology, making truly portable receivers possible, beginning with transistor radios in the late 1950s.

Current trend in Radio receivers is to use digital circuitry on the chip to do functions that were formerly done by analog circuits which require passive components.