Radios

In the works by Larissa Gartner (lgartner7)

Radios

Radios are everywhere. Between the music in a car or coded messages in a war, radios are important to life. To create a radio wave, you use electromagnetism. Circuits, resisitors and capacitors are used. With Radios people can create anything and communicate. Here is a video to watch and learn about how radios inspire those around you. Radio ad by MTN.

How it works

Radio waves are a type of electromagnetic wave. They travel through the air at the speed of light. These waves can be produced through circuits. Through the acceleration of charged particles, radiation is created. This radiation is in the form of Electromagnetic Radiation. Circuits are used with capacitors to create this accelerated particle. Mathematically you can portray these waves as sine or cosine waves. These have a fixed frequency and follow the formula Asin(w+phase). A is amplitude, w is the angular frequency and phase is the amount the wave is displaced from the origin.

In general, the more complex the circuit is, the more you can control the wave using resisters, capacitors and general sparks. See the circuit model, below, to see a basic radio circuit.

There is a difference between FM and AM radios. It depends on how the information is carried. FM uses a carrier signal, another signal that just sends the data of the songs. AM uses one sine signal.

Experiements

Here are some simple radio experiments, from this website, to help better your understanding on how radios work.

Simple Test One

Take a new 9-volt battery and a quarter.

Use an AM radio and tune it to channel with static.

Hold the battery near the antenna and tap the two terminals on the battery with the coin. Keep connecting this and un-connecting this.

The connection and disconnection of the coin onto the battery creates a crackle in the radio.

This test shows how any circuit can produce these waves, if the charged particle is accelerating.

Simple Test Two

Use a metal file and two wires.

Connect the file's handle to one terminal a 9-volt battery.

Connect the one piece wire to the other terminal, and run wire up and down the file.

In the dark, you can see a small 9-volt sparks along the file.

If you hold the file next to an AM radio you will hear static.

Connection

Signals like radio waves are used in many classes at Tech. For computer engineering students, they must take Digital Signal Processing. This teaches about the understanding of and applying sine waves. Students adjust the waves to produce sounds using Matlab. Growing up many students listened to the radio. This also has been used to broadcast important news. People use radios in everyday. Walkie-talkies use these signals to communicate with each other by setting them at the same frequency. Many computer and electrical engineers study the use and application of these electromagnetic waves. It allows people to distribute data through circuits. This helps people to better understand how computers and other data devices.

A Circuit Model

This is a basic radio wave circuit. Mathematically you can find the resistance, capacitance and current of the circuit. L is a coil. C is a capacitor. R is a resistor.The triangle in the top right corner oscillates to produce a wave.

A Computational Model

Here is a Matlab program that creates a sound out of waves. Radio waves have specific frequencies that can be heard with the human ear. This code specifically generates a siren so you can see and hear the wave. Click this link to download the Matlab code. I recommend starting the code with makesiren(250,200,.5,8000,1,10).

History

There is a lot of debate on who created the first radio. In 1894 a man named Guglielmo Marconi became interested in the work of the physicist Heinrich Hertz. Hertz discovered waves that were produced from Electromagnetic interaction. From this information, Marconi started to create wave making equipment. With this equipment, he started to send signals in a mile radius. Nikola Tesla is said to have created plans for a radio in 1892. By 1896 Tesla created a radio-controlled robotic boat. He drove this boat in the waters of Manhattan from Madison Square Garden using a remote. At the same time, Marconi was broadcasting up to a 12 mile radius, with help from the British Post Office. By 1899 his signal was sent and recieved across the English Channel. Marconi started to work towards a transatlantic radio signal. By 1901, he created such signal, as well as a long-distance wireless telegraph. Tesla claimed he created the Telegraph in 1893.

In 1909 Marconi received a noble peace prize for his work in radio.

Fun fact! (also sad fact) Marconi Company Radios were used on the Titanic in 1912. These radios helped the crew contact Carpathia, another boat, to pick up the survivors.

In 1943 the US Supreme Court discredited some of Marconi's patents because of Tesla's work.

See also

There is a lot of information on radios. Between amateur radio clubs, readings and history, you can find a lot of interesting facts about radios.

Amateur radio clubs can help you build radios. Some even send signals to space. To find one near you click here

Further reading

Carr, Joseph J. Old Time Radios!: Restoration and Repair. Blue Ridge Summit, PA: Tab, 1991. Print.

Rosenthal, Phil. "'Turnaround Year' Predicted for CBS Radio." Tribunedigital-chicagotribune. Chicago Tribune, 05 Dec. 2007. Web. link

Lazaroff, Leon. "Satellite Radio Sending out Strong Signal." Tribunedigital-chicagotribune. Chicago Tribune, 02 Oct. 2005. link

External links

Understanding Circuts

Testla Theory

History

Understanding Radio Waves

Experiments

References

References used while writing this page.