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58 Cards in this Set
- Front
- Back
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_________ results from the fact that the speed of a signal through a medium is diffrent for diffrent frequencies.
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delay distortion
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_______ occurs when the signal meets an obstical and some of the signal reflects.
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Return loss
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In this technique the sender generates a pseudorandom sequence of numbers that dictate which frequencies will be used and the order in which they are used.
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Frequency Hopping Spread Spectrum.
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Why is fiber immune to noise.
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because it uses light instead of electrical current
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________ when signals travel through multiple pairs of wire and the speed varies from wire to wire.
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Delay skew
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BNC T-connector is used for _____?
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coax
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High frequency radio transmissions can do what?
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carry a higher data rate than low frequency
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____ is only suitable for low speeds because the receiver must re-tune itself every time the frequency changes.
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FHSS
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The ___ regulates the wireless frequency spectrum in the United States.
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FCC
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__________ frequency can go through walls easy.
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Low
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When a wireless signal reflects off an object and multiple copies of the same signal arive at the receiver it is called ___________?
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multipath
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Approxmatily there are _______ frequencies in the radio spectrum but not all are usable for communication.
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300 million
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Name the 3 types of wired media.
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1 Coax
2 Twisted pair 3 Fiber optics |
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Compents in the atmoshpere like water and oxygen absorb wireless signals, this is called _______?
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atmospereric absorption
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Wireless transmission can suffer from five main impairments.
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1 free-space loss
2 atmosphere absorption 3 multipath 4 refraction 5 thermal noise |
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Is higher or lower frequencies effected more by atmospheric absorption?
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high
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This impairment deals with wireless signals dispersing over distance.
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Free-space loss
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Name some disadvanteages of coax cable.
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1 more expensive and thicker than twisted pair
2 stiff and hard to work with 3connectors are more prone to failure |
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Plastic fibers can be used for ________ ________ only.
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short distances
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Fiber is made of ________ or _________.
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glass or plastic
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The more twists in a twisted pair means it is more immune from ______.
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noise
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name the two damaging effects caused by multipath.
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1 Since the receiver will receive to copies of the same signal they will interfere with each other
2 receiver might get multiple copies of the same signal |
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Fiber can send transmission in haow many directions?
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one
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Name five major transmission impairments for copper and fiber optic media.
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1 Attebuation
2 Delay distortion 3 noise 4 return loss 5 delay skew |
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Multipath is a big problem with _______.
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cell phones
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What are the two types of light sources used with fiber.
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LED and laser
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_________ is a problem with satelite signals due to their weak signals.
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Thermal noise
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The __connector is the most common type of fiber connector used today.
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ST
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Are short wave or long wave lasers more common.
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Shortwave lasers are more common...the are similar to those in cd players
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LEDs are used for _____.
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low speed applications (10-100Mbps).
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SC and ST connectors are used for?
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fiber
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Excessive bending and pulling and compression can increase _________.
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crosstalk
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___________ works by combining the signal with a pseudo-random sequence that serves to spread the signal accross the entire spectrum at once.
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Direct Sequence Spread Spectrum
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Thermal noise is also called _______ noise.
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white.
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______________ is used when wire media will not work. ie across cities or a nation via satelites.
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microwave
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Name the three bands used for commercial satelites.
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C
Ku Ka |
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_________ results from the thermal agitation of electrons.
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Thermal noise
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_______ is the result of unwanted electrical signals.
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Noise
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Electromagnetic interference or radio frequency interference causes _____ noise?
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impulse
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_______ is the bending of radio waves due to atmospheric conditions.
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refraction
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_____ is caused by signals in adjacent wires.
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Crosstalk
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RJ-45 connectors are used with ____?
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UTP
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What causes impulse noise?
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Electromagnetic interference or radio frequency interference.
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On the surface of the earth maximum distance between microwave antennas is ________ because of the curvature of the earth.
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30 miles
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Lightning causes _____ noise.
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impulse
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An ___________ signal spreads out in all directions and can be received by many antennas spread around the transmitting antenna.
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omnidirectional
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Wire spices, imperfections in the cable and the cable connectors are examples of what causes _________.
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return loss
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Describe Geostationary eath orbit (GEO)
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orbits at 22,300 miles above earth. Matches the rotation on earth and appears to be statioanry in the sky.
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Name the three main types of wireless media.
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1 Microwave
2 Radio 3 Infrared |
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Medium earth orbit (MEO)
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orbits 6K - 12K miles up. only "visible" for 2-4 hours each orbit.
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Microwaves uses frequencies between ____ and _____GHz.
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2 and 40
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Name the four parts to a coax cable
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1 Outer jacket
2 sheilding 3 dielectric insulation 4 conductor |
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Current minimum standard for twisted pair is __________.
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Cat5E
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Two techniques to implement spread spectrum.
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DSSS and FHSS
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Long wavelengths =
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Long distances
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How are wireless transmissions and receptions accomplished?
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With antennas
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Low earth orbit (LEO).
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Orbits 500-1000 miles up and is the fastest of the three categories. Only visible for 15 minutes each orbit.
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A ___________ signal is a narrow focused bean that requires the sending and receiving antennas to be carefully aligned.
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directional
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