What is AFC in communication?

Automatic frequency control (AFC) is employed in radio and television receivers, FM transmitters, radar systems, satellite transceivers, and frequency synthesizers to maintain frequency stability.

What is AFC in CRT TV?

A horizontal automatic frequency control (AFC) circuit is a primary circuit for driving a cathode ray tube (CRT) display. … The horizontal deflection driver 307, in responsive to the horizontal driving pulse 313, controls horizontal deflection for the CRT 308.

What is the automatic frequency control voltage of the FM transmitter VCO?

DC voltage 2) The automatic frequency control voltage of the FM transmitter VCO is DC voltage. 2) AGC maintains a constant level of the output signal based on the received signal nature. 3) AGC adjusts the gain of RF and IF amplifiers according to need. 4) AGC can handle problems like overloading and fading in the receiver.

What is AFC wireless?

The Wi-Fi Alliance has released their first draft specification of the so-called ‘Automatic Frequency Coordination‘ (AFC) function – an online database lookup scheme required for Wi-Fi to operate at standard power. The specification is a critical step towards allowing 6 GHz Wi-Fi to operate outdoors.

Why mixing is used in communication?

Mixers are widely used to shift signals from one frequency range to another, a process known as heterodyning, for convenience in transmission or further signal processing. … Frequency mixers are also used to modulate a carrier signal in radio transmitters.

What is AFC voltage?

In radio equipment, Automatic Frequency Control (AFC), also called Automatic Fine Tuning (AFT), is a method or circuit to automatically keep a resonant circuit tuned to the frequency of an incoming radio signal. … This error voltage is then fed back to the tuning circuit in such a way that the tuning error is reduced.

What is Armstrong method of FM generation?

From Wikipedia, the free encyclopedia. In 1933, Edwin H. Armstrong patented a method for generating frequency modulation of radio signals. The Armstrong method generates a double sideband suppressed carrier signal, phase shifts this signal, and then reinserts the carrier to produce a frequency modulated signal.

What is the role of amplitude limiter in the FM receiver?

In FM receiver, role of amplitude limiter is to amplify low frequency signals. Explanation: Amplitude Limiter circuit is used in FM receiver to remove the noise or any variation in amplitude present in the received signal. Thus, the output of the amplitude limiter has a constant amplitude.

What does aft mean on a TV?

AFT means Automatic Frequency Tune, sometimes named AFC (Automatic Frequency Correction) and have the origin on the first FM radios and TV tuners. AFT use a DC feedback from the output of the detector to control the Local Oscillator. Oct 17, 2006.

What are the characteristics of radio receiver?

The basic performance characteristics of a radio receiver are sensitivity, selectivity, and stability. Sensitivity is the capability of receiving weak radio signals, where signal strength may be as low as 10–19 watt for a signal whose frequency bandwidth is approximately 1 kilohertz.

How does automatic gain control work?

The AGC circuit keeps the receiver’s output level from fluctuating too much by detecting the overall strength of the signal and automatically adjusting the gain of the receiver to maintain the output level within an acceptable range.

What is the horizontal scanning frequency of a monochrome TV receiver?

In the North American monochrome system, 525 scan lines are transmitted about 30 times per second, for a horizontal sweep frequency of 525 × 30 = 15,750 hertz.

What is fidelity in receiver?

Fidelity of a receiver is its ability to reproduce the exact replica of the transmitted signals at the receiver output. For better fidelity, the amplifier must pass high bandwidth signals to amplify the frequencies of the outermost sidebands, while for better selectivity the signal should have narrow bandwidth.

What is RF image rejection?

The image rejection ratio, or image frequency rejection ratio, is the ratio of the intermediate-frequency (IF) signal level produced by the desired input frequency to that produced by the image frequency. The image rejection ratio is usually expressed in dB.

What is double spotting?

Double spotting is a condition where the same desired signal is detected at two nearby points on the receiver tuning dial. One point is the desired point while the other is called the spurious or image point. … Poor front-end selectivity and inadequate image frequency rejection leads to double spotting.

What is the difference between TRF and superheterodyne receiver?

In a TRF receiver the high amplitude original frequency is demodulated at the detector stage. … In TRF receiver, amplification is not constant over the tuning range. In superhet receiver amplification standard is constant since all the time it amplifies a constant frequency at the IF stages.

What is if of superheterodyne FM receiver?

Figure (a) shows the block diagram of an FM receiver. The output of the IF amplifier is applied to the limiter circuit. The limiter removes the noise in the received signal and gives a constant amplitude signal. This circuit is required when a phase discriminator is used to demodulate an FM signal.

What is fidelity in analog communication?

Explanation: Fidelity is the ability of the receiver to reproduce all modulating signals, equally, without any distortion. … It is the ability to amplify weak signals.

What is RF tuning?

A tuned radio frequency receiver (or TRF receiver) is a type of radio receiver that is composed of one or more tuned radio frequency (RF) amplifier stages followed by a detector (demodulator) circuit to extract the audio signal and usually an audio frequency amplifier. This type of receiver was popular in the 1920s.

What is RF tuner?

Tuners are a primary part of receiver circuit, and they receive RF signals from the antenna and convert the selected carrier frequency and its associated bandwidth into a fixed frequency. The output of tuner is fed into RF amplifier for further processing.

Why if frequency is 455 kHz?

Uses. Perhaps the most commonly used intermediate frequencies for broadcast receivers are around 455 kHz for AM receivers and 10.7 MHz for FM receivers. … A first intermediate frequency may even be higher than the input signal, so that all undesired responses can be easily filtered out by a fixed-tuned RF stage.

Why is superheterodyne receiver used?

The superheterodyne receiver offers superior sensitivity, frequency stability and selectivity. Compared with the tuned radio frequency receiver (TRF) design, superhets offer better stability because a tuneable oscillator is more easily realized than a tuneable amplifier.

What is selectivity of receiver?

Selectivity (radio), a measure of the performance of a radio receiver to respond only to the radio signal it is tuned.