Term
| State the purpose of a transmission line. |
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Definition
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The purpose of a transmission line is transfer energy from a source to a load by electronic means.
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Term
| What are the two basic types of transmission lines? |
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Definition
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The two basic types of transmission lines are balanced and unbalanced lines.
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Term
| Define balanced and unbalanced lines. |
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Definition
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Balanced – Both wires carry RF, but voltage and current are 180 degrees out of phase. Unbalanced – One conductor is carrying the RF, the other conductor is at a different potential.
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Term
| Define balanced and unbalanced lines. |
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Definition
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Balanced – Both wires carry RF, but voltage and current are 180 degrees out of phase. Unbalanced – One conductor is carrying the RF, the other conductor is at a different potential.
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Term
| Calculate the wavelengths for lines 1 km long operated at (a) 1 kHz, (b) 50 kHz, and (c) 7.5 MHz. |
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Definition
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a. 300,000 meters. b. 6,000 meters. c. 40 meters.
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Term
| Explain the concepts of source and load. |
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Definition
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Source is anything that generates energy. Referred to as a repeater or transmitter. A load is anything that consumes energy.
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Term
| Explain the concept of traveling waves. |
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Definition
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Traveling waves are any RF that is connected or applied to a transmission line.
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Term
| What is meant by a properly terminated line? |
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Definition
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A properly terminated line is all of the energy from a source is absorbed by the load. All the energy is transferred by the transmission line.
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Term
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Definition
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Resonant line – A transmission line that is not properly terminated.
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Term
| Explain how standing waves are formed. |
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Definition
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Standing waves are formed by any RF energy that is not consumed by the load will return to the source.
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Term
| Explain how standing waves are formed. |
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Definition
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Standing waves are formed by any RF energy that is not consumed by the load will return to the source.
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Term
| What device is used to measure SWR on a coaxial cable? |
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Definition
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To measure SWR on a coaxial cable, a Wattmeter is used.
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Term
| Define characteristic impedance. |
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Definition
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The amount of inductance, capacitance, and resistance in a transmission line is characteristic impedance. It is determined by the diameter of the conductors or the spacing of the wire.
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Term
| List and describe the three major types of losses for transmission lines. |
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Definition
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The three major types of losses for transmission lines are copper losses, dielectric losses, and radiation losses.
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Term
| Briefly describe the three classifications of radio wave propagation. |
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Definition
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1. Ground wave – RF travels along surface of earth. Direct wave – RF travels from transmitter to receiver. Sky wave – RF sent from earth, reflects of atmosphere, and back to earth to the receiver.
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Term
| How can ground wave coverage by increased? |
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Definition
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Ground wave coverage can be increased by using vertical polarization.
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Term
| How can the range of space wave transmissions be increased? |
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Definition
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The range of space (direct) wave transmissions can be increased by increasing the height of either the transmission or receiving antennas.
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Term
| Define radio horizon and explain how it occurs. |
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Definition
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Radio horizon – Any RF that travels further than your visible horizon. It occurs because the RF curves along with the surface of the earth.
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Term
| For long distance communications, which of the wave propagation classifications is used most? |
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Definition
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For long distance communications, sky wave propagation is used most.
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Term
| Define (a) critical frequency (b) critical angle. |
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Definition
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a. Critical frequency – Highest frequency of the RF that will still reflect off the atmosphere. MUF b. Critical angle – Highest angle that can still be reflected back to earth.
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Term
| Explain the concept of multiple-hop transmission. |
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Definition
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Multiple hop transmission is when the RF reflects off the atmosphere and back to earth multiple times. Six times to make one complete revolution around earth.
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Term
| How can skip distance be maximized? |
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Definition
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Skip distance can be maximized by increasing the frequency and decreasing the angle.
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Term
| Describe the effects of multipath reception. |
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Definition
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The effects of multipath reception are fading and interference.
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Term
| Describe the four categories of variations that affect the ionosphere. |
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Definition
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The four categories of variations that affect the ionosphere are diurnal, geographical, cyclical, and seasonal.
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Term
| How can the range of communications in the VHF, UHF, and higher frequencies be extended? |
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Definition
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A satellite and tropospheric scatter can extend the range of communications in the VHF, UHF, and higher frequencies.
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Term
| Explain the concept of tropospheric scatter. |
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Definition
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Tropospheric scatter is the use of RF that reflects off the troposphere, but most of the energy is scattered in other directions.
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