Development of Communication Technology

Buni Yani

Group 3: MKT 11 – 3C

Ananda Zata
Arimbi Lestari
Chandra Wibowo

Julius Sasmita
Sunshza Wilhelmina
Talita

RADIO FREQUENCES

A radio wave is an electromagnetic wave propagated by antenna. Radio waves have different frequencies, and by tuning radio receiver to a specific frequency you can pick up a specific signal.

All FM radio station transmits in a band of frequencies between 88 megahertz and 108 megahertz. Megahertz mean "millions of cycles per second," example "91,5 megahertz" means that the transmitter at the radio station is oscillating at a frequency of 91.500.000 cycles per second. So, you can tune your radio on that specific frequency and it will give u clear reception of that station. Same way with AM radio, it is confined to a band from 535 kilohertz to 1.700 kilohertz (kilohertz meaning "thousands," so 535.000 to 1.700.000 cycles per second).

Common Frequency bands include the following:
    -AM radio - 535 kilohertz to 1.7 megahertz.
    -Short Wave Radio - Bands from 5.9 megahertz to 27.41 megahertz.
    -Citizens Band (CB) radio - 26.96 megahertz for channels 2 trough 6.
    -FM Radio - 88 megahertz to 108 megahertz.
    -Television Stations - 174 to 220 megahertz for channels 7 through 13.

Why is AM radio in a band at 550 kilohertz to 1.700 kilohertz, while FM radio is in a band at 88 to 108 megahertz? It is completely arbitrary, and a lot of it has to do with history.

AM radio has been around a lot longer than FM radio. The first radio broadcasts occurred in 1906 or so, and frequency allocation for AM radio occurred during the 1920s (the predecessor to the FCC was establishing by congress in 1927). In 1920s, radio and electronic capabilities were fairly limited, hence the relatively low frequencies for AM radio.

FM radio was invented by a man named Edwin Armstrong in order to make high-fidelity (and static-free) music broadcasting possible. He built the first station in 1939, but FM did not become really popular until the 1960s

television stations were pretty much non-existent until 1946 or so, which is when the FCC allocated commercial broadcast bands for TV. By 1949, a million people owned TV sets, and by 1951 there were 10 million TVs in

America

Radio frequency (RF) is a frequency, or rate of oscillation, of electromagnet radiation within the range of about 3 Hz to 300 GHz. This range corresponds to the frequency of alternating current electrical signals used to produce and detect radio waves. Since most of this range is beyond the vibration rate that most mechanical systems can respond to, RF usually refers to oscillations in electrical circuits (An electrical circuit is a network that has a closed loop, giving a return path for the current. A network is a connection of two or more components, and may not necessarily be a circuit).

Radio communication

In order to receive radio signals, for instance from AM/FM radio stations, a radio antenna must be used. However, since the antenna will pick up thousands of sine waves (The sine wave or sinusoid is a function that occurs often in mathematics, music, physics, signal processing, audition, electrical engineering, and many other fields) at a time, The sine wave is important in physics because it retains its wave shape when added to another sine wave of the same frequency and arbitrary phase. It is the only periodic waveform that has this property. This property leads to its importance in Fourier analysis and makes it acoustically unique. radio tuner is necessary as well to tune in to a particular frequency (or frequency range). This is typically done via a resonator (in its simplest form, a circuit with a capacitor and an inductor). The resonator is configured to resonate at a particular frequency (or frequency band), thus amplifying sine waves at that radio frequency, while ignoring other sine waves. Usually, either the inductor or the capacitor of the resonator is adjustable, allowing the user to change the frequency it resonates at.

XM Radio

While XM Radio and Sirius have merged into a single company, the two services aren't fully integrated yet. Part of the reason for this is due to differences in hardware and software.

XM Radio uses two Boeing HS 702 satellites, appropriately nicknamed "Rock" and "Roll," and two BSS 702 satellites it calls "Rhythm" and "Blues," placed in parallel geostationary orbit, two at 85 degrees west longitude and the other two at 115 degrees west longitude. Geostationary Earth orbit (GEO) is about 22,223 miles (35,764 km) above Earth, and is the type of orbit most commonly used for communications satellites. The first XM satellite, "Rock," was launched on March 18, 2001, with "Roll" following on May 8 of the same year. A design flaw in the HS 702 satellite caused its solar panels to function inefficiently. XM launched "Rhythm" on February 28, 2005, and "Blues" on October 30, 2006, to replace the older satellites. Then XM Radio powered down "Rock" and "Roll." The older satellites remain in orbit and can serve as backups, if necessary.