Radio Waves

By Bina Vekaria

What are Radio Waves and how do they work?• Radio waves are an unseen form of electromagnetic radiation

which fluctuates in wavelength from a millimetre to 100,000 km. This makes it have the widest range on the electromagnetic spectrum.

• When they are transmitted they hit the ionosphere and bounce back to a receiver.

• Marconi was the patent who first came up with the idea of wireless telegraphy.

You can see that radio waves take up quite a lot of range on the electromagnetic spectrum

Examples of Devices that use Radio Waves:

•Mobile Phones

•Television

•Satellite Navigation

•Radars

•Microwave

Mobile phones• Mobile phones do use electromagnetic radiation.

• The type they use is Microwave.

• A transmitter takes your voice and encodes it onto a sine wave

• This signal is then transmitted to an antenna which then emits it into the atmosphere

• These waves are then picked up by a mobile phone tower.

• The mobile phone network provider then sends this signal back to the mobile phone

Television• The typical television signal needs a bandwidth of 4 Hz, however

that’s just for the visual so if you include sound and some space for it to buffer it will require 6 Hz

• This is the reason there are three chunks of 6Hz bandwidths for TV on the spectrum:

• 54 to 88 MHz for channels 2 to 6 • 174 to 216 MHz for channels 7 through 13 • 470 to 890 MHz for UHF channels 14 through 83• The amalgamated video signal is then amplitude-modulated into the

appropriate frequency, and the sound signal is frequency-modulated as a separate signal

• The tuner in your TV removes the merged video and sound signal for that channel from the radio waves received by the aerial.

• These radio waves have been sent by the broadcaster and then picked up by an antenna.

Satellite Navigation• Satellite Navigation devices use the Global Positioning System

satellites to locate your position it does this through three satellites.

• Each of these satellites transmit information being received from the signal been given out by the sat nav device. It uses this information from all three to come to a conclusion as to where you are positioned.

• Once it knows where you are it then has the complex task of finding the shortest route to your destination. This is come to by a lot of different calculations by the satellites.

• The map is a large set of vectors. So the latter is used to calculate the most ideal route, using the longitude and latitude.

Radars• There are three main purposes for radars:

▫ To detect an object in the distance▫ To calculate or identify the speed of an object ▫ To map out something

• You can use an echo of a sound to perceive how far away it is and you can use the Doppler Shift to figure out how fast the echo of the sound is going which would make it possible to create a sound radar also known as a sonar.

• Sonars are used by boats and submarines but on land it is difficult to use sound through the air. Sound doesn’t travel very far and the echo of sound in air is very hard to detect because it’s quite faint.

• This is when Radio waves come in. Radio waves can travel far are easy to detect even when faint and are invisible to humans.

• This is why they are used to detect airplanes because with the long distances that the planes travel you would need to know where they are so radio waves come in handy

Microwaves

• Microwaves work from the benefit of water molecules subjected to electromagnetic waves.

• The water molecule is dipole meaning that one side is positively charged the other being negative. The electromagnetic waves in a microwave are in the frequency bandwidth of 2.5 GHz

• Since the electromagnetic waves consist of electric fields. The positive charge in the electric field pulls the positive charged side of the dipole in one direction and the negative charge of electric field pulls the negative charge of the dipole in the other direction.

• This means it has a direct effect on the water molecule forcing them to rotate quickly and uniformly. The kinetic energy from the rotation of these water molecules is then converted to heat energy in turn heating up the food.

Conclusion• In conclusion, there are many types of radio waves in devices that we use

everyday. Some times these radio waves are considered to be harmful such as in mobile phones and microwaves but other times they save lives with things such as the radars.

• Radio waves also prove to be very versatile and seem to have great uses in todays world. Satellite navigation is a great example of how it has helped make our lives easier. No more worrying about whether to keep your eyes on the road or the map.

• Microwave is the most awesome use of radio waves, especially from a student’s point of view. It means people are able to cook things quickly in today’s busy lifestyle.

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