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57 Cards in this Set
- Front
- Back
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What connecting link is used to transfer energy from a radio transmitter to its antenna located on the mast of a ship?
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Transmission Line
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What terms are used for the end of the transmission line that is connected to a transmitter? (5)
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a) input end
b) generator end c) transmitter end d) sending end e) source |
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What terms are used for the end of the transmission line that is connected to an antenna? (4)
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a) output end
b) receiving end c) load end d) sink |
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Name the five types of transmission lines in use today.
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1) parallel two-wire
2) twisted pair 3) shielded pair 4) coaxial line 5) waveguide |
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Name the three main uses of a two-wire open line.
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Power lines
Rural telephone lines Telegraph lines |
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What are the two primary disadvantages of a two-wire open line?
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High Radiation Losses
Noise Pickup |
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What type of transmission line is often used to connect a television set to its antenna?
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Twin lead
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What is the primary advantage of the shielded pair?
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The conductors are balanced to ground
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What are the two types of coaxial lines in use today?
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Air Coaxial (rigid)
Solid Coaxial (flexible) |
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What is the chief advantage of the air coaxial line?
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The ability to minimize radiation losses
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List the three disadvantages of the air coaxial line.
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a) Epensive to construct
b) Must be kept dry c) High frequency losses limit the practical length of the line |
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List the two common types of waveguides in use today.
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Cylindrical
Rectangular |
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What are the three types of line losses associated with transmission lines?
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Copper
Dielectric Radiation |
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Losses caused by skin effect and the I2(sqrd)R (power) loss are classified as what type of loss?
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Copper losses
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What types of losses cause the dielectric material between the conductors to be heated?
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Dielectric losses
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What must the physical length of a transmission line be if it will be operated 15,000 Hz?
Use the formula λ=V/f |
λ=20 meters
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List three physical factors that determine the values of capacitance and inductance of a transmission line?
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(1) Type of line used
(2) Dielectric in the line (3) Length of line |
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A transmission line is said to have distributed constants of inductance, capacitance, and resistance along the line. What units of measurement are used to express these constants?
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Inductance- in microhenrys per unit length
Capacitance- in picofarads per unit length, Resistance- in ohms per unit length |
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Describe the leakage current in a transmission line and in what unit it is expressed.
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Leakage Current: the small amount of current that flows through the dielectric between two wires of a transmission line.
Expressed in= Microhms per unit length |
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All the power sent down a transmission line from a transmitter can be transferred to an antenna under what optimum conditions?
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When the characteristic impedance of the transmission line and the load impedance are equal.
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What symbol is used to designate the characteristic impedance of a line, and what two variables does it compare?
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Z₀
and it is the ratio of E to I at every point along the line |
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What is the range of the characteristic impedance of lines used in actual practice?
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Between 50 and 600 ohms
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Two types of waves are formed on a transmission line. What names are given to these waves and how do they flow?
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INCIDENT WAVES from generator to load.
REFLECTED WAVES from load back to generator. |
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On an open-ended transmission line, the voltage is always zero at what distance from each end of the line?
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One-fourth the distance from each end of the line
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A nonresonant line is a line that has no standing waves of current and voltage on it and is considered to be flat. Why is this true?
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The load impedance of such a line is equal to Z₀
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On an open line, the voltage and impedance are maximum at what points on the line?
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Even quarter-wave points (1/2λ, λ, 3/2λ, etc.)
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At what point on an open-circuited rf line do voltage peaks occur?
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At 1/2 wavelength from the end and at every 1/2 wavelength along the line.
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What is the square of the voltage standing-wave ratio called?
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Power standing-wave ratio (pswr)
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What does vswr measure?
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The existance of voltage variations on a line
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_______ _______ are devices for guiding electical energy from one point to another.
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Transmission Lines
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_______ _______ is the ratio of voltage to current at the input end of a transmission line.
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Input Impedance
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What type of parallel line is used for power lines, rural telephone lines, and telegraph lines?
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Two-Wire Open Lines
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What type of line is normally used to connect televisions to their antennas?
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Twin Lead
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What type of line consists of two insulated wires twisted together?
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Twisted Pair
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What type of line has parallel conductors seperated by a solid dielectric and surrounded by copper braided tubing?
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Shielded Pair
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What type of line has high radiation losses and is subject to noise pickup?
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Two-Wire Open Lines
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What type of line has conductors that are balanced to ground?
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Shielded Pair
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What type of line has high insulation loss?
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Twisted Pair
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What type of line contains two concentric conducors insulated from each other by spacers?
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Rigid Coaxial Line
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What type of line consists of a flexible inner conductor and a concentric outer conductor of metal braid which are seperated by a continuous insulating material?
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Flexible Coaxial Lines
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_______ are hollow metal tubes used to transfer energy from one point to another?
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Waveguides
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What type of line is pressurized with an inert gas to prevent moisture from entering?
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Rigid Coaxial Line
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What type of losses can result from (IxIxR) loss, in the form of heat, or skin effect?
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Copper Losses
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What type of line has the lowest amount of high frequency losses?
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Rigid Coaxial Line
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What type of loss decreases the conductivity of a line?
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Copper Loss
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Does the energy in waveguides travel FASTER or SLOWER than in free space?
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Slower
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Dielectric Losses are caused by......
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The heating of the dielectric material between conductors.
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Radiation and Induction Losses are caused by......
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Part of the electromagnetic fields of a conductor being dissipated into SPACE or NEARBY OBJECTS.
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What kind of loss takes power away from the source?
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Dielectric Losses
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A transmission line is either electrically LONG or SHORT if its physical length is not equal to ____λ
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1/4λ
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Theoretical properties (inductance, resistance, capacitance) of a transmission line that are combined into a single component are known as _______ _______.
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Lumped Constants
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Constants of inductance, resistance, and capacitance that are spread along the transmission line are known as _______ _______.
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Distributed Constants
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Where does LEAKAGE CURRENT flow?
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Between the wires of a transmission line through the dielectric.
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In Leakage Current, what type of component does the dielectric act as?
A capacitor, inductor, resistor, or transistor? |
Resistor
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What type of FIELD exists along a transmission line when current flows through it?
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Electromagnetic
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For maximum transfer, the CHARACTERISTIC IMPEDANCE and the _______ IMPEDANCE must be matched.
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Load
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A transmission line that is not terminated in its characteristic impedance is said to be _______.
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Finite
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