Amplitude modulation or AM as it is often called, is a form of modulation used for radio transmissions for broadcasting and two way radio communication applications. Although one of the earliest used forms of modulation it is still in widespread use today. The first amplitude modulated signal was transmitted in 1901 by a Canadian engineer named Reginald Fessenden. He took a continuous spark transmission and placed a carbon microphone in the antenna lead. The sound waves impacting on the microphone varied its resistance and in turn this varied the intensity of the transmission. Although very crude, signals were audible over a distance of a few hundred metres, although there was a rasping sound caused by the spark. With the introduction of …show more content…
The resistor is used to enable the capacitor to discharge. If it were not there and no other load was present, then the charge on the capacitor would not leak away, and the circuit would reach a peak and remain there. Advantages of Amplitude Modulation, AM There are several advantages of amplitude modulation, and some of these reasons have meant that it is still in widespread use today: * It is simple to implement * it can be demodulated using a circuit consisting of very few components * AM receivers are very cheap as no specialised components are needed. Disadvantages of amplitude modulation Amplitude modulation is a very basic form of modulation, and although its simplicity is one of its major advantages, other more sophisticated systems provide a number of advantages. Accordingly it is worth looking at some of the disadvantages of amplitude modulation. * It is not efficient in terms of its power usage * It is not efficient in terms of its use of bandwidth, requiring a bandwidth equal to twice that of the highest audio frequency * It is prone to high levels of noise because most noise is amplitude based and obviously AM detectors are sensitive to it. Summary AM has advantages of simplicity, but it is not the most efficient mode to use, both in terms of the amount of space or spectrum it takes up, and the way in which it uses the power that is transmitted. This is the reason why it is not widely used these days both for
Moving beyond the modern day technology that aides the common citizens, there is also an abundant amount of technology that aides in police work such as facial recognition, iris scans and mobile data terminals. Many people don’t understand how simple, yet beneficial facial recognition is in the police work. When first hearing facial recognition many minds may jump to some complex idea but the process is quite easy in fact even simple social networking
Transmission interferences: Weather, terrain, and the range from the nearest signal point can all interfere with signal reception. Reception in tunnels, some buildings, and rural areas is often poor.
Because the voltage used to transmit data needs only be high enough for the receiver to detect it. Making the voltage higher would make the receiver electronics more difficult.
Health professionals are more involved in the assessment of the child’s development, these include health visitors, GP and specialist nurses.
The personal frequency modulation system consists of a transmitter microphone used by the speaker and a receiver used by the person needing assistants as the listener.
During World War II the navy had developed highly intelligent radio communications. The navy began using both telegraph,telephone(loud voice amplifiers)
On old radios the antenna was detrimental to the radio’s operation. Today, the antenna is not necessary. AM radio does not have as good of quality as FM but it can travel farther distances. FM signals can be interfered by things such as mountains or other barrier
1. In your opinion, what is the purpose of our dropping the transmit power to such a low level?
One monumental advancement was launched on November 2nd 1920 when “The first Commercial radio station was born, and a new era had dawned”(Radio). The radio became the fastest way to share important information and connected
When radio first arrived to the scene, it was not automatically made available to consumers. Initially, the United States Navy had control of the wireless telegraph communication during World War I. All of amateur and commercial usage stopped when the United States participated in the war; instead, stations were taken over by government control. Radio developed gradually during the first decade of the twentieth century. It was not until 1920 when conglomerates owned radio stations. Even at that point, many people did not predict radio to have the power it did later on. Without knowing it, radio would soon permanently change the lives of individuals around the world.
and difficult to intercept also this transmission can share a frequency band with many types
The radio was never used more—or for a much more important reason—than during World War I and World War II. Prior to the first world war war, many ships used the radio for communication. In the early part of the 20th Century, amplification was one of the top concerns of the development of the radio. Of course people were able to communicate with others hundreds of miles away, but the clarity and amplification of the messages weren’t necessarily as good as many had expected and counted on. Often times, other means of communication—like the telegraph—were better off being used instead of the radio. Because of that, Lee De Forest invented the Audion vacuum tube in 1906, and followed that up one year later by adding his triode tube. According to
“In 1913, Edwin Armstrong invented a special circuit that made long-range radio transmission of voice and music practical” (American). This technological advancement made it convenient to use the radio as means of delivering the news. Whether you lived in a rural countryside or in a packed city, you were able to get the news. Able to broadcast weather reports, sports news, and entertainment to thousands of Americans, the radio proved to be an invaluable resource.
Some sources state that Leon Scott had the first device known as the Phonoautograph in 1857. However the feeling in most research is that because no proof of any recording can be found he was not listed as the first to succeed. Almost all research that I have done and any readings state that Thomas Edison was the first to make the first recording of the human voice in 1877. The recording was of a human voice reciting “Mary had a little lamb”. This was
a much deeper sound and have a much lower frequency than what you are used to hearing. When