# Are You Aware Of How The Application Of Resonance In Radio Tuning Works?

###### Synopsis

This article on radio tuning explains the science behind how radio receivers filter and amplify signals using resonance in tuned circuits. It is important for precise tuning and enabling multiple stations to use the same frequency band. It is relevant for Class 12th students studying Physics as it provides a detailed explanation of the principles of radio tuning, preparing them for future studies in electrical engineering or computer science.

###### Synopsis

This article on radio tuning explains the science behind how radio receivers filter and amplify signals using resonance in tuned circuits. It is important for precise tuning and enabling multiple stations to use the same frequency band. It is relevant for Class 12th students studying Physics as it provides a detailed explanation of the principles of radio tuning, preparing them for future studies in electrical engineering or computer science.

Have you ever wondered how your radio is able to tune into your favourite station while you're on the go? The answer lies in the science of radio tuning and the crucial role of resonance in selecting a specific frequency from the many that are present in the airwaves. In this article, we will explore the mechanics of radio tuning and how resonance is used to filter out unwanted frequencies and amplify weak signals. Whether you're a student or a radio enthusiast, come along and discover the fascinating world of radio tuning and the application of resonance.

## What Are Tuned Circuits?

When you turn on a radio or TV, a lot of things happen inside the receiver before you can hear the sound or see the picture from the station that is broadcasting. There are many signals that reach the antenna of the receiver at the same time, but to pick a specific station, you adjust the tuning dial on the receiver to select the desired station and reject the unwanted signals. This selection process happens with the help of a circuit called a tuned circuit, which is made up of a coil and a capacitor that are connected together. When the circuit has the right combination of inductance and capacitance, it creates a phenomenon called resonance, which helps to pick the desired signal.

## Resonant Circuit

When a specific frequency is applied to an LCR circuit, it causes the reactance of the inductor (XL) and the reactance of the capacitor (Xc) to be equal. This is when the circuit is in a state of resonance. This only happens at one specific frequency, which is called the resonant frequency. This principle is what allows tuned circuits in radio receivers to pick a specific frequency and ignore all the others.

This is the reason XL and XC are given so much attention. It demonstrates how a coil and a capacitor are connected either in series (view (A)) or in parallel (view (B)) in a basic tuned circuit. Typically, the resistance mechanism of the components, especially the resistance of the coil, is all that the circuit's resistance (R) may be.

One of the key advantages of using a resonant circuit in radio tuning is its ability to filter out unwanted frequencies. When a radio station's frequency is received by the antenna, it induces a current in the resonant circuit that is in phase with the received frequency. At the same time, other frequencies that are not in phase with the resonant circuit are not amplified and are effectively filtered out. This allows the radio to tune into a specific station and reject other unwanted signals, leading to a clear and stable reception.

After an extensive study of resonance circuits, we will examine one of their major applications: the radio receiver. In radio and television receivers, series and parallel resonant circuits are frequently used to tune in stations and isolate the audio signal from the radio frequency carrier wave.

Working

Let's look at the Block Diagram of the Superheterodyne AM Receiver which is given below and how it works.

The incoming amplitude-modulated radio waves are received by the antenna, which contains many different frequencies from different broadcasting stations. To select just one of these incoming waves, a resonant circuit (or a bandpass filter) is used. A weak signal is chosen, and it is gradually amplified to create an audible audio-frequency wave. The audio amplifier is used to amplify the audio signal before it reaches the loudspeaker, the intermediate frequency (IF) amplifier to amplify an internally generated signal based on the radio frequency (RF) signal, and the radio frequency (RF) amplifier to amplify the chosen broadcast signal

The so-called superheterodyne receiver uses a heterodyne circuit, a frequency mixer, to maintain the audio frequencies carried by the incoming signal while producing the same IF signal (445 kHz) consistently. The local oscillator is connected to the RF amplifier to generate an RF signal that is mixed with the incoming signal by the frequency mixer, resulting in an output signal containing a combination of the two input signals' frequencies, including the sum and the difference frequencies. The original audio signal is extracted in the detector stage, where the IF signal is removed, leaving the audio signal. The audio signal is then amplified to drive the loudspeaker, which converts the electrical signal to sound. The tuning circuit for the AM radio receiver is a crucial part of the receiver, which is used to select the desired station from the many frequencies present in the airwaves.

## The History Of Radio Tuning

Recent advancements in radio tuning have focused on the use of digital technology to improve the quality and stability of radio reception. One of the most significant advancements in this area is the development of software-defined radio (SDR). SDR is a type of radio that can be configured and controlled using software, rather than traditional hardware-based components. This allows for more flexibility and a wider range of frequencies to be tuned, with higher precision and stability.

Another advancement in radio tuning is the use of digital radio technology. Digital radio, also known as digital audio broadcasting (DAB), uses digital technology to deliver radio broadcasting. This provides several benefits over traditional analog radio, including better sound quality, greater resistance to interference, and the ability to transmit additional information such as song titles and artist information.

Additionally, many new technologies are emerging like cognitive radio, which uses artificial intelligence and machine learning algorithms to improve the radio tuning process and make it more efficient. It's a software-defined radio technology that makes the radio automatically tune into the best frequency, avoiding interference and optimising communication.

Overall, recent advancements in radio tuning have greatly improved the quality and stability of radio reception and opened new possibilities for the future of radio communication.

## Real-life Applications Of Resonance In Radio Tuning

Apart from the radio receiver, here are some examples of real-life applications of resonance in radio tuning:

• Analog radio receivers: In traditional analog radio receivers, a resonant circuit is used to select a specific frequency from the many that are present in the airwaves. The circuit is designed to have a high Q factor, which means that it has a high selectivity and a high amplification factor for a specific frequency. This allows it to amplify weak signals and increase the sensitivity of the radio receiver.

• Mobile phones: Resonant circuits are used in mobile phones to select and amplify the desired frequency of the cellular signal and filter out unwanted frequencies. This allows for clear and stable communication between devices.

• WiFi routers: WiFi routers also use resonant circuits to select and amplify the desired frequency of the wireless signal and filter out unwanted frequencies, providing a stable wireless connection.

• Satellite dishes: Resonant circuits are used in satellite dishes to select and amplify the desired frequency of the satellite signal and filter out unwanted frequencies, providing a clear and stable satellite TV or radio reception.

• Remote-controlled devices: In radio-controlled devices such as remote-controlled cars and drones, resonant circuits are used to select the specific frequency of the remote control signal and filter out any interference from other signals. This ensures a stable and reliable connection between the remote control and the device it is controlling.

Resonance plays a critical role in radio tuning by allowing for the selection and amplification of a specific frequency while filtering out unwanted frequencies in various real-life applications such as analog radio receivers, mobile phones, WiFi routers, satellite dishes, and remote-controlled devices. This ensures a clear and stable connection for communication and control.

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