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Coax cables traditionally consist of a single, two-conductor wire, with a center conductor and an outer shield/conductor, which is of solid metal. Sometimes braided or stranded metal is used. Twinaxial cables contain two such configurations within a single cable sheath. As the center conductor carries the carrier signal and the outer conductor generally is used for electrical grounding and is maintained at 0 volts, coax is described as an unbalanced medium. Coax connectivity can be extended through the use of twisted pair, with a BALUN (BALanced/UNbalanced) connector serving to accomplish the interface.
The gauge of coax is thicker than twisted pair. While this increases the available bandwidth and increases the distance of transmission (less resistance), it also increases the cost. Traditional coax is quite thick, heavy and bulky of which Ethernet LAN coax (10Base5) is an example. ThinNet, or CheaperNet, (10Base2) coax is of much lesser dimensions, but offers less in terms of performance.
The effective capacity of coaxial cable depends on several factors, including the gauge of the center conductor, the length of the circuit, and the spacing of amplifiers and other intermediate devices. The available bandwidth over coax is very significant, hence its use in high capacity applications, such as data and image transmission. As examples, the following are coax standards for Ethernet LANs, with 10Base5 involving more substantial cable, with a thicker center conductor than is the case with 10Base2:
As in the case of UTP, 100 Mbps is possible over coax, and over longer distances with better error performance. In CATV and other applications, coax routinely supports transmission of multiple channels at an aggregate rate of 500 MHz.
Coax performs exceptionally well, due to the outer shielding. As a result, it is often used in data applications.
Coax is not so limited as UTP, although amplifiers or other intermediate devices must be used to extend high frequency transmissions over distances of any significance.
Coax is inherently quite secure. It is relatively difficult to place physical taps on coax. Additionally, little energy is radiated.
The acquisition, deployment, and rearrangement costs of coax are very high, compared with UTP. In high capacity data applications, however, that cost is often outweighed by its positive performance characteristics.
Historically, coax was often used in telephone company interoffice trunking applications, as a superior option to twisted pair cables. However, that is no longer the case as satellite, microwave, and fiber optic cable are the media of contemporary choice in such applications. Yet, coaxs superior performance characteristics make it the favored medium in many short haul, bandwidth-intensive data applications. Current and continuing applications include LAN backbone, host-to-host, cabinet-to-cabinet (PBX & computer), host-to-peripheral (e.g., host-to-Front End Processor), and CATV.
Ah, heres the problemthe keyboard and hard drive are fine. The trouble seems to be that your monitor is a microwave.
From the comic strip Bizarro by Dan Piraro
Microwave radio, a form of radio transmission which uses ultra-high frequencies, developed out of experiments with radar (radio detecting and ranging) during the period preceding World War II. The first primitive systems, used in military applications in the European and Pacific theaters, could handle up to 2,400 voice conversations over 5 channels. Developed by Harold T. Friis and his associates at Bell Laboratories, the first public demonstration was conducted between the West Street lab and Neshanic, New Jersey in October 1945 [3-6].
There are several frequency ranges assigned to microwave systems, all of which are in the GigaHertz (GHz) range; in other words, billions of cycles per second. The wavelength is in the millimeter range; that is to say that each cycle or wave is in the range of a millimeter, with billions of such cycles generated during a second of transmission. This very short wavelength gives rise to the term microwave. Such high frequency signals are especially susceptible to attenuation and, therefore must be amplified (analog) or repeated (digital) frequently. Therefore, if the transmit and receive microwave radio antennae are separated by a considerable distance, there must be intermediate antennae at periodic intervals in order to boost the signal.
In order to maximize the strength of such a high frequency signal and, therefore, to increase the distance of transmission at acceptable levels, the radio beams are highly focused. The transmit antenna is centered in a concave, reflective metal dish which serves to focus the radio beam with maximum effect on the receiving antenna, as illustrated in Figure 3.4. The receiving antenna, similarly, is centered in a concave metal dish, which serves to collect the maximum amount of incoming signal.
Figure 3.4 Point-to-point microwave.
The requirement to so tightly focus the signal clearly limits the application of microwave. It is a point-to-point, rather than a broadcast, transmission system. Additionally, each antenna must be within line of sight of the next antenna, as such high frequency radio waves will not pass through solid objects of any significance (buildings, mountains, or airplanes). Given the curvature of the earth, and the obvious problems of transmitting through it, microwave hops generally are limited to 50 miles (80 km.).
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