Guru
Introduction
In the vast landscape of technological advancements, few inventions have had as profound an impact on communication as radio. The ability to transmit and receive information wirelessly has not only revolutionized the way we access news and entertainment but has also played a pivotal role in connecting the world. This blog explores the fascinating history of radio broadcasting, delving into the principles of transmission and reception that have shaped this transformative medium.
The process of sending radio or T.V. signals by an antenna to multiple receivers which can simultaneously pick up the signal is called ‘broadcasting’.
In simple words ‘to radiate radio waves from a station into space’ is called broadcasting or, to send signal in all directions (broad) is called broadcasting.
After the waves are thrown into the space, the transmission starts and all the receivers in ‘the range’ can simultaneously pick up the signal. This is called ‘reception’. There is a little difference between broadcasting and transmission.However, the process of reception is quite different.
Important components of a typical network are under: See below Figure.
- Broadcasting
- Microphone: At the broadcasting station, the person speaks before mike. The mike is a transducer and converts sound energy into electrical energy. The speaker generates a sound of frequency between 20 Hz and 20 kHz (i.e., audio frequency).
- Amplifier: The electrical signal obtained from microphone (mike) is weak and the same is amplified through an amplifier(s) to the required strength.
- Modulator: Here the modulation of the signal occurs. A local oscillator generates high frequency waves called ‘carrier’. The signal modulates the carrier or the signal is superimposed on the carrier. The resultant waves are called radio waves or modulated waves.
- Transmitting antenna: Through the transmitting antenna, the radio waves are propagated into the space.
2. Transmission
- After broadcasting, the transmission starts. These radio waves travel in space at a speed of 3 × 108 m/s, as they are electromagnetic waves.
3. Reception
- The picking of these radio waves by radio (or T.V.) receiver is called reception. A radio receiver has the following important parts:
- Receiving antenna: The radio waves induced an e.m.f. on the antenna.
- RF amplifier: The radio waves are of radio frequency (R.F.) range. The e.m.f. induced is amplified through R.F. amplifier(s).
- Detector: Now the original signal is detected (separated) from the carrier by the detector circuit.The signal starts its forward journey while the carrier is grounded.
- A.F. amplifier: The signal is now passed through the amplifier.Note that now the signal is of audio frequency range. It should have sufficient energy to strike the loudspeaker.
- Loudspeaker (L.S.): This is the final stage. The electric signal is again converted into the original sound signal which was produced in the broadcasting station:
Note:
- Here ‘Radio’ does not mean radio receiver. The ‘radio’ means wireless.
- Radio means ‘radiations for wireless transmission’.The principle of radio broadcasting,transmission and reception described above is same for radio,T.V. signals and also for all such wireless devices.
- Radio is the abbreviated form of ‘radio telegraph or radio telephone.
- Broadcasting means to ‘send out’ in all directions. It may be:
- A.M. radio broadcast band: Its range is 540–1600 kHz. The stations are assigned every 10 Hz in the above band.
- F.M. radio broadcast band: Its range is 88–108 MHz. The stations are assigned every 200 Hz in the above band.
- T.V. broadcasting band: A T.V. channel is 6 MHz wide to include picture and sound signals for each broadcast station.
5.Analog and digital broadcast signal
- Analog form of a broadcast signal is a continuous variation as shown in Fig. 1 (a),
- Digital form of broadcast signal is shown in Fig. 1 (b).
Figure 1
REASONS OF ERRORS IN COMMUNICATION SYSTEM
When a distortion occurs in the received message, an error is said to have occurred. The distortion may be a frequency, phase or any other distortion.
There are following reasons which produce errors:
- Band Width: When the bandwidth allowed to a transmission is not sufficient it causes an error. The bandwidth allowed to the AM transmission is only 10 kHz but a human ear requires a bandwidth of 15 kHz for full satisfaction. Hence AM transmission lacks fidelity.The bandwidth allowed to F.M. transmission is 200 kHz and it can reproduce a transmitted signal to our full satisfaction.
- Noise: The unwanted sound is called noise. The noise is another reason that produces error. There are many types of noises: external or internal.The signal to noise ratio can be improved by changing the band width.
TYPES OF COMMUNICATION SYSTEMS
- The electronic communication systems according to medium are of following types:
- Wire communication: i.e., where communication is done through wires, e.g., cable T.V., wire telephony, etc.The wires may be made of galvanised steel. See Fig. 2.
- Wireless or carrier communication: i.e., where communication is done without wires. In this system, a carrier wave is used. In other words, modulation is carrier out, e.g.radio, T.V., radar, telephony, etc.A carrier is a high frequency wave which ‘carries’ the signal, i.e.,the signal is ‘superimposed’ on the carrier. See Fig. 3.
- Optical fibre communication: An optical fibre cable (OFC) consists of an inner glass core surrounded by glass cladding and then a protective covering. (Fig. 4).Digital signals are transmitted in the form of intensity modulated light signals,which are trapped in the glass core of the cable. The signal is detected on the other side, using a photo device.This communication is used above `10^{10}`Hz frequencies.
- Satellite communication: In this, the signals are transmitted and received through a satellite positioned in the space.
- Wave guide communication: In this communication, wave guides are used. These are used for frequencies of `10^{8}` to `10^{10}` Hz.
- Co-axial cables communications: The co-axial cables are used for `10^{5}` to `10^{8}` Hz.
Figure 2
Figure 3
Figure 4
- The communication may be also classified as Analog and digital communication: In the analog communication, the signal is modulated and transmitted directly.
In digital communication, the analog signal before transmission is converted into digital signal. See Fig. 5.
Figure 5
The Birth of Radio Broadcasting:
The story of radio begins with the groundbreaking work of inventors such as Guglielmo Marconi and Nikola Tesla in the late 19th and early 20th centuries. Marconi's successful demonstration of wireless telegraphy marked the birth of practical radio communication. Radio broadcasting, however, truly took off in the 1920s, as pioneers like Lee De Forest and Edwin Armstrong developed technologies that allowed for the transmission of audio signals.
Principles of Transmission
1.Electromagnetic Waves
Therefore, radio transmission utilizes electromagnetic waves. The waves propagate at the speed of light that allows to transmit information for long distances without using wires. The wavelength and the distance over which a signal can travel are determined by radio frequencies as measured in hertz, that is Hz.
2.Modulation
To modulate is the process through which radio waves transfer audio information. Two major processes are employed – amplitude modulation (AM) and frequency modulation (FM). In AM the amplitude of carrier wave is changed and in this way FM enables frequency adjustment. Amplying FM, sound-quality provider of signal is used that has overtaken the majority of music and voice communications.
3.Transmitters
Radio transmitters change audio signals into radio waves. Such doing devices, starting from broadcast posts to complete stations significantly boost and transmit signals over a cleanup frequency; all communications share the appropriate target.
Principles of Reception
1.Antennas
The reception of radio signals significantly depends on antennas. Such equipment picks up the electromagnetic waves that are reverted back to electrical signals, which can be run by this radio receiver.
2.Radio Receivers
Radio receivers used in radios and car stereos, pick specific frequencies by tuners which users can select. The demodulation of the signal by receiver results in restoration of original audio which can be reproduced through a speaker or head-phones.
3.Demodulation
The demodulation process is reciprocal to the modulation applied in transmission, hence restoring the pristine audio signal. This enables the listeners to listen clearly and in a digital form.
4.Radio's Impact on Society
The invention of radio broadcasting triggered a communication revolution radically changing the way people get and make use of information. In the golden age of radio, with magical dramas performed live by celebrities to current-day podcasts is very popular.
Conclusion
It is imperative that we recognize the significant influence of radio broadcasting on international communication as we navigate the digital era. Radio continues to be a dynamic and significant force in the rapidly shifting media and communication landscape because the transmission and reception principles that underpin this technology have not only withstood the test of time but have also undergone further development. Thus, the next time you tune into your preferred podcast or station, pause to recognize the technological marvel and rich history of radio.