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Radio, and Wireless Internet Technology
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LOOK INSIDE! books above and read the pages indicated. Starting 2014, I will assign reading from the books that provide free readings in LOOK INSIDE! readings that are relevant to current topic..
AM Receivers and RF spectrum
"The term Radio Frequency (RF or rf) refers to the electromagnetic field that is generated when an alternating current is input to an antenna. This field, also called an RF field or radio wave, can be used for wireless broadcasting and communications over a significant portion of the electromagnetic radiation spectrum -- from about 9 kilohertz (kHz) to thousands of gigahertz (GHz). This portion is referred to as the RF Spectrum. As the frequency is increased beyond the RF spectrum, electromagnetic energy takes the form of infrared (IR), visible light, ultraviolet (UV), X rays, and gamma rays." from Spread Spectrum Scene
Antennas, Decibels, and Space flight Telecommunications
"The antenna is the most visible part of the satellite communication system. The antenna transmits and receives the modulated carrier signal at the radio frequency (RF) portion of the electromagnetic spectrum. For satellite communication, the frequencies range from about 0.3 GHz (VHF) to 30 GHz (Ka-band) and beyond. These frequencies represent microwaves, with wavelengths on the order of one meter down to below one centimeter. High frequencies, and the corresponding small wavelengths, permit the use of antennas having practical dimensions for commercial use. This article summarizes the basic properties of antennas used in satellite communication and derives several fundamental relations used in antenna design and RF link analysis." from Antennas:The Interface with Space
Network and the Internet
The infrastructure that supports all these layers was in place prior to the explosion in the use of the Internet. The telephone companies provided connectivity over the entire World. By 1960 It was recognized circuit connectivity could not support data transfer between computers all of the World, and the concept of packet switching was agreed upon. Right Click Here and in New Tab read about Networks!
Internet Network Infrastructure:
Dialup: Twisted pair telephone
line transfer data at audio frequency
DSL: The same twisted pair telephone lines are use to transfer Data at much higher than audio frequency range, taking advantage of the fact that twisted pairs have natural band pass of approximately 1.0 MHZ.
Four types of physical Networks
"A LAN (local area network) is a group of computers and network devices connected together, usually within the same building. By definition, the connections must be high speed and relatively inexpensive (e.g., token ring or Ethernet). Most Indiana University Bloomington departments are on LANs.
A LAN connection is a high-speed connection to a LAN. On the IUB campus, most connections are either Ethernet (10Mbps) or Fast Ethernet (100Mbps), and a few locations have Gigabit Ethernet (1000Mbps) connections.
A MAN (metropolitan area network) is a larger network that usually spans several buildings in the same city or town. The IUB network is an example of a MAN.
A WAN (wide area network), in comparison to a MAN, is not restricted to a geographical location, although it might be confined within the bounds of a state or country. A WAN connects several LANs, and may be limited to an enterprise (a corporation or an organization) or accessible to the public. The technology is high speed and relatively expensive. The Internet is an example of a worldwide public WAN. " Quote from Indiana University Site."
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