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EXPLORATIONS - The Story of Radio

时间:2006-03-15 16:00来源:互联网 提供网友:z75531   字体: [ ]
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EXPLORATIONS - The Story of Radio
By Paul Thompson

Broadcast: Wednesday, June 01, 2005

(MUSIC)

VOICE ONE:

This is Steve Ember.

VOICE TWO:

 
Satellite technology can broadcast radio anywhere. 
And this is Faith Lapidus with the VOA Special English program EXPLORATIONS. You are listening to our program today on a radio. Almost no communication would exist in the world without the electromagnetic waves that make radio possible. Today we explain the history of radio and tell how it works.

(MUSIC)

VOICE ONE:

Our story begins in Britain in eighteen seventy-three. A scientist named James Maxwell wrote a mathematical theory about a kind of energy. He called this energy electromagnetic waves. His theory said this kind of energy could pass unseen through the air. Mister Maxwell was not able to prove his idea. Other scientists could not prove it either until German scientist Heinrich Hertz tried an experiment in eighteen eighty-seven.

VOICE TWO:

Mister Hertz's experiment sounds very simple. He used two pieces of metal placed close together. He used electricity to make a spark jump between the two pieces of metal.

He also built a simple receiver made of wire that was turned many times in a circle or looped. At the ends of the loop were small pieces of metal separated by a tiny amount of space. This receiver was placed several meters from the other device.

Mister Hertz proved that Mister Maxwell's idea was correct. Electromagnetic waves or energy passed through the air from one device to the other.

VOICE ONE:

Later, Mister Hertz demonstrated the experiment to his students in a classroom. One of the students asked what use might be made of this discovery. But Mister Hertz thought his discovery was of no use. He said it was interesting but had no value. He was wrong. His experiment was the very beginning of every kind of electronic communications we use today. In recognition1 of his work, the unit of frequency of a radio wave, one cycle per second, is named the hertz.

VOICE TWO:

Radio waves became known to scientists as Hertzian Waves. But the experiment was still of no use until Guglielmo Marconi improved on the device that created Hertzian Waves. He began his experiments in Italy in eighteen ninety-four.

Mister Marconi was soon able to transmit sound across a distance of several kilometers. He tried to interest Italian government officials in his discovery, but they were not interested.

Mister Marconi traveled to Britain. His invention was well received there. In eighteen ninety-seven, he established the Wireless2 Telegraph and Signal Company. The company opened the world's first radio factory in Chelmsford, England in eighteen ninety-eight.

(MUSIC)

VOICE ONE:

Very quickly, people began sending and receiving radio messages across long distances using equipment made by Mister Marconi's company.

Ships at sea needed the device. Before Mister Marconi's invention, they had no communication until they arrived in port. With radio, ships could call for help if they had trouble. They could send and receive information.

All of Mister Marconi's radios communicated using Morse code. It sounds like this. What you will hear are three letters. V---O---A. We will repeat, or send, each group of three letters two times.

(MORSE CODE: V-O-A…V-O-A)

An expert with Morse code could send and receive thirty or forty words a minute. Mister Marconi's radio greatly increased the speed of communications.

VOICE TWO:

On December twenty-fourth, nineteen-oh-six, radio operators on ships in the Atlantic Ocean near the American coast began hearing strange things. At first it was violin music. Then they heard a human voice. The voice said "Have a Merry Christmas."

That voice belonged to a man named. He hadbeen working on producing a device

 
The voice of Reginald Fessenden was the first to be heard on Radio.
that could transmit the human voice or music using radio. He decided3 to try it for the first time on December twenty-fourth. It was the first time a human voice had been heard on radio.

VOICE ONE:

Improvements in radio technology now came more quickly. Large companies became interested. Broadcasting equipment and radio receivers were improved.

Fourteen years after Mister Fessenden's voice was heard by radio operators at sea, the first real radio broadcast was transmitted. It came from the city of Pittsburgh, Pennsylvania.

The radio program was transmitted on radio station KDKA on the evening of November second, nineteen twenty. The man speaking on the radio was Leo Rosenberg. He was announcing the early results of the presidential election between James Cox and Warren Harding.

Within a year, the little radio station employed the world's first full-time4 radio announcer. His name was Harold Arlin. KDKA in Pittsburgh is still a successful radio station today. Oh…and Mister Harding won the presidential election!

(MUSIC)

VOICE TWO:

Those first KDKA broadcasts led to the success of the radio industry. People began buying the first radios. Other companies decided radio could make a profit. Only four years after the first KDKA broadcast, there were six hundred radio stations in the United States. Radio stations also began to broadcast in other countries.

Radio stations began selling "air time" as a way to pay their workers and to pay for needed equipment. A few minutes of air time were sold to different companies so they could tell about their products to the radio station's listeners. This method of supporting radio and later television is still used today.

VOICE ONE:

Radio changed the way people thought and lived. It permitted almost everyone to hear news about important events at the same time. Political candidates could be heard by millions of listeners. The same songs were heard across the country.

The work by British scientist James Maxwell and German scientist Heinrich Hertz led to the development of modern communications technology. This includes television broadcasts, satellite use, cellular5 telephones, radio-controlled toys, and much more.

(MUSIC)

VOICE TWO:

Now we will explain electromagnetic waves. We will begin with Mister Hertz's experiment. You can also try this experiment. It is very easy to do. First, move the controls on your radio to an area where no station is being received.

Now, you will need a common nine-volt battery and a metal piece of money. Hold the battery near the radio and hit the top of the battery with the coin. You should hear a clicking noise on the radio.

Your coin and battery are a very simple radio transmitter. This radio will not transmit very far. However, if you know a little of Morse code, you could communicate with this device.

VOICE ONE:

Electromagnetic energy travels almost like an ocean wave – up and down, up and down. It also travels at the speed of light – two hundred ninety-nine million seven hundred ninety-two thousand four hundred fifty-eight meters each second.

Scientists have learned how to separate radio waves into different lengths called frequencies. This permits many radio stations to broadcast at the same time and not interfere6 with each other.

Most radio frequencies around the world are named after Heinrich Hertz. For example, one popular radio station in Washington, D.C. broadcasts on six hundred thirty kilohertz. This is called a medium wave. The kilo means thousand. The hertz means cycles or waves per second.

VOICE TWO:

You may be hearing our broadcast on what is called short wave. These are frequencies between three thousand and thirty thousand kilohertz. They are often called megahertz. Mega means a million. One megahertz is the same as one thousand kilohertz.

Short wave is good for broadcasting very long distances. The short wave signals bounce off the ionosphere that surrounds the Earth, back to the ground and then back to the ionosphere.

Short wave can be heard for very long distances, but sometimes the signal is not clear. However, radio technology continues to improve. Today, VOA broadcasts to satellites in space that send the signal back to stations on the ground that transmit programs with a clear signal.

It is even possible today to use a computer to link with thousands of radio stations around the world. We think Mister Hertz would be very proud of the little device he thought would never be of any use.

(MUSIC)

VOICE ONE:

This program was written by Paul Thompson. It was produced by Mario Ritter. This is Steve Ember.

VOICE TWO:

And this is Faith Lapidus. Join us again next week for another EXPLORATIONS program in Special English on the Voice of America.


点击收听单词发音收听单词发音  

1 recognition zUYxm     
n.承认,认可,认出,认识
参考例句:
  • The place has changed beyond recognition.这地方变得认不出来了。
  • A sudden smile of recognition flashed across his face.他脸上掠过一丝笑意,表示认识对方。
2 wireless Rfwww     
adj.无线的;n.无线电
参考例句:
  • There are a lot of wireless links in a radio.收音机里有许多无线电线路。
  • Wireless messages tell us that the ship was sinking.无线电报告知我们那艘船正在下沉。
3 decided lvqzZd     
adj.决定了的,坚决的;明显的,明确的
参考例句:
  • This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
  • There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。
4 full-time SsBz42     
adj.满工作日的或工作周的,全时间的
参考例句:
  • A full-time job may be too much for her.全天工作她恐怕吃不消。
  • I don't know how she copes with looking after her family and doing a full-time job.既要照顾家庭又要全天工作,我不知道她是如何对付的。
5 cellular aU1yo     
adj.移动的;细胞的,由细胞组成的
参考例句:
  • She has a cellular telephone in her car.她的汽车里有一部无线通讯电话机。
  • Many people use cellular materials as sensitive elements in hygrometers.很多人用蜂窝状的材料作为测量温度的传感元件。
6 interfere b5lx0     
v.(in)干涉,干预;(with)妨碍,打扰
参考例句:
  • If we interfere, it may do more harm than good.如果我们干预的话,可能弊多利少。
  • When others interfere in the affair,it always makes troubles. 别人一卷入这一事件,棘手的事情就来了。
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TAG标签:   exploration  story  radio  exploration  story  radio
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