Come holidays and it is difficult to stay off gadgets – mobile phones, computers, televisions, etc. But have you wondered what was the source of such entertainment when your grandparents were kids? In those times, the gadget that children and grown-ups alike used to look forward to were the radios. I am sure your exposure to radios is limited to the songs you listen to when on a drive in your car or likewise. But believe me, the radio is a very good source of information as well as entertainment. So how does a radio work? Let us explore it further.
“Radio waves” transmit information ranging from music, conversations, pictures, and data through the air, often over millions of miles. These are means of broadcasting electromagnetic signals to carry information from one place to another. Even though radio waves are invisible and completely undetectable to humans, they have been and still remain an integral part of society. Instruments like cell phones, monitoring devices, cordless phones, and many other wireless devices use radio waves to communicate. Some other technologies that you may use every day like the AM and FM radio broadcasts, automatic Garage door openers, Radio-controlled toys Television broadcasts GPS receivers Ham radios Satellite communications Police radios Wireless clocks, radar and microwave ovens all use radio waves.
Things like communication and navigation satellites, modern aviation would be impossible without radio waves. The current trend toward wireless Internet access uses radio as well!¬ The funny thing is that, at its core, radio is an incredibly 
simple technology. With just a couple of simple electronic components, you can easily build basic radio transmitters and receivers. A machine that sends out radio signals is called a transmitter while the one that picks up the signals is called a receiver. There are devices with both functions combined and they are called transceivers. When radio signals are sent out from a transmitter to many receivers simultaneously it is called a broadcast. Guglielmo Marconi is said to have invented the radio.
Simple Transmitters: Using a 9-volt battery one could create radio waves that could be received by an AM radio. In fact, if done carefully one can even see sparks along the connecting wires as they touch each other. When this setup is held near an AM radio a lot of the weird static noise can be heard. The radio transmitters during the early days were called spark coils and they created a continuous stream of sparks at voltages as high as 20,000 volts.
At these voltages, the waves could travel much farther. This method however is now replaced with continuous sine waves.
The reason that we use continuous sine waves today is that there are so many different people and devices that want to
use radio waves at the same time. There is a huge array of radio waves functional simultaneously for TV broadcasts, AM and FM radio broadcasts, police and fire radios, satellite TV transmissions, cell phone conversations, GPS signals, and so on. Each different radio signal uses a different sine wave frequency, and that is how they are all separated.
Such a sine wave and a transmitter that is transmitting the sine wave into space with an antenna make a radio station. In other words, any company that produces and broadcasts radio programs using this technology is referred to as radio stations. The only problem is that the sine wave doesn’t contain any information. You need to modulate the wave in some way to encode information on it.
There are three common ways to modulate a sine wave:
- Pulse Modulation – In PM, you simply turn the sine wave on and off like a morse code.
- Amplitude Modulation – Both AM radio stations and the picture part of a TV signal use amplitude modulation to encode information. In amplitude modulation, the amplitude of the sine wave (its peak-to-peak voltage) changes.
So, for example, the sine wave produced by a person’s voice is overlaid onto the transmitter’s sine wave to vary its amplitude. - Frequency Modulation – FM radio stations and hundreds of other wireless technologies (including the sound portion of a TV signal, cordless phones, cell phones, etc) use this mode of transmission. In this, the sound wave is converted to frequencies based on the input sound signal. The FM mode is less prone to static noise and that proves to be a great advantage in the clarity of the transmission. Since natural and artificial noise sources are less present at these frequencies, high-quality audio transmission is possible, using frequency modulation.
Radio satellites are used to receive and transmit radio waves even from space. In satellite television and satellite radio systems, the radio signal is encrypted and can only be decrypted by the receiver, which is controlled by the company and can be deactivated if the customer doesn’t pay his bill. Broadcasting uses several parts of the radio spectrum, depending on the type of signals transmitted and the desired target audience. Long-wave and medium-wave signals can give reliable coverage of areas several hundred kilometers across, but have the more limited information-carrying capacity and so work best with audio signals (speech and music), and are subject to natural and artificial sources of interfering noise. The shortwave bands have a greater potential range but are more subject to interference by distant stations and varying atmospheric conditions that affect reception.
So that’s all about Radios and the way they work. The next time you tune into your favorite radio channel or use a cordless phone, remember how these invisible waves help us in this mode of communication.
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