By Armitha Raras.D
FACULTY OF SOCIAL AND POLITICAL SCIENCES
UNIVERSITY OF PELITA HARAPAN
The person who introduced the electromagnetic waves for the first time is James Clerk Maxwell at London University. Then in 1879 George F. FritzGerald proposed the oscillatory currents produced by capacitor charging through inductor might generate Maxwell's waves. Radio waves are one from of electromagnetic radiation. This is the other forms of infrared radiation, light, ultraviolet radiation, X-rays, and Gamma rays. In each forms of electromagnetic radiation consists of oscillatory electric and magnetic filed transverse wave that travel through space at a speed of about 300.000 km per second (180.000 miles per second). Information, which sends through radio wave, will face interference. To overcome the interference then the standard technique is to combine the signal containing the information with a much higher frequency carrier wave in a process called modulation. Pulse modulation and single side band is usually used for radiotelephony, radiotelegraphy telemetry and other services. The pulse modulation is divided into pulse-amplitude modulation (PAM), pulse-position modulation (PPM), and pulse-duration modulation (PCM). Single side band (SSB) is divided into lower side band and upper side band. The components of radio technology consists of:
a.Power supply is a direct current power supplying the radio frequency oscillator. b.Radio frequency oscillator it converts the power to determine by its dimensions. c. Frequency multiplier.
d.Radio frequency amplifier.
e.Modulator combines the amplified radio-frequency signal.
f.Audio frequency multiplier
g.Transmission line electrical transmission line connects the transmitter to the transmitting antenna. h.Antenna is designed to launch to an electromagnetic wave or to intercept a fraction of a transmitted wave for reception.
The main point is that the role of vibration. Every voice and sound can be heard because there are vibrations from 20 kHz up to 20.000 kHz. This vibration then manipulated the magnetic produced by electricity and then becomes the electromagnetic. The electromagnetic becomes wave through the air and may reach everywhere to a far distance. The principle of radio waves makes possible to other media electronic communication such as television, radio astronomy, radar, and etc. Later development then the electromagnetic can be replaced by light wave as it called laser i.e. light amplification by emission radiation. The audio movie film had been fantastic developed without realizing by the spectators or audience. There are so many experiments had been made to improve the audio movie film technology by using digital, subwoofer speaker, Dolby system, time code, etc. the sound of movie film is not producing one audio channel but it has developed into multi audio channel.
Since 1939 the audio film technology showed slowly progress. But until the 1950's it was found a magnetic strip for 35 and 70 mm. In 35-mm film cinemascope as 20th Century Fox product equipped by four magnetic tracks each for left and right and its surroundings. Since 1950 till 70s decade the audio of film movie is still progressing in static, in form of mono optical or two-channel stereo. Then in 1970 Dolby began to use matrix technique which change medium of 2 tracks optic stereo became 4 channel audio front left, front center and front right and it's surroundings with mono audio systems. The Cinema Digital Sound (CDS) is the first medium digital audio in 1990 using for film bioscope, produced in cooperation with Optical Radiation Corporation (ORC) with Eastman Kodak Company. Mr. Dick Tracy produced for the first time using 70-mm film accompanied by using audio CDS. The CDS is the first sophisticated digital technique recorded in form of bitmap without data compression. The pattern of bitmap has lots of small pixels. The Kodak...