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effective 7/01/2016 thru 6/29/2020

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2016-E9F: Transmission lines: characteristics of open and shorted feed lines; 1/8 wavelength; 1/4 wavelength; 1/2 wavelength; feed lines: coax versus open-wire; velocity factor; electrical length; coaxial cable dielectrics; velocity factor

2016-E9F01: What is the velocity factor of a transmission line?

The velocity of the wave in the transmission line divided by the velocity of light in a vacuum

The ratio of the characteristic impedance of the line to the terminating impedance

The index of shielding for coaxial cable

The velocity of the wave in the transmission line multiplied by the velocity of light in a vacuum



2016-E9F02: Which of the following determines the velocity factor of a transmission line?

Dielectric materials used in the line

The termination impedance

The line length

The center conductor resistivity



2016-E9F03: Why is the physical length of a coaxial cable transmission line shorter than its electrical length?

Electrical signals move more slowly in a coaxial cable than in air

Skin effect is less pronounced in the coaxial cable

The characteristic impedance is higher in a parallel feed line

The surge impedance is higher in a parallel feed line



2016-E9F04: What is the typical velocity factor for a coaxial cable with solid polyethylene dielectric?

0.66

2.70

0.30

0.10



2016-E9F05: What is the approximate physical length of a solid polyethylene dielectric coaxial transmission line that is electrically one-quarter wavelength long at 14.1 MHz?

3.5 meters

20 meters

2.3 meters

0.2 meters



2016-E9F06: What is the approximate physical length of an air-insulated, parallel conductor transmission line that is electrically one-half wavelength long at 14.10 MHz?

10 meters

15 meters

20 meters

71 meters



2016-E9F07: How does ladder line compare to small-diameter coaxial cable such as RG-58 at 50 MHz?

Lower loss

Higher SWR

Smaller reflection coefficient

Lower velocity factor



2016-E9F08: What is the term for the ratio of the actual speed at which a signal travels through a transmission line to the speed of light in a vacuum?

Velocity factor

Characteristic impedance

Surge impedance

Standing wave ratio



2016-E9F09: What is the approximate physical length of a solid polyethylene dielectric coaxial transmission line that is electrically one-quarter wavelength long at 7.2 MHz?

6.9 meters

10 meters

24 meters

50 meters



2016-E9F10: What impedance does a 1/8 wavelength transmission line present to a generator when the line is shorted at the far end?

An inductive reactance

A capacitive reactance

The same as the characteristic impedance of the line

The same as the input impedance to the final generator stage



2016-E9F11: What impedance does a 1/8 wavelength transmission line present to a generator when the line is open at the far end?

A capacitive reactance

The same as the characteristic impedance of the line

An inductive reactance

The same as the input impedance of the final generator stage



2016-E9F12: What impedance does a 1/4 wavelength transmission line present to a generator when the line is open at the far end?

Very low impedance

The same as the characteristic impedance of the line

The same as the input impedance to the generator

Very high impedance



2016-E9F13: What impedance does a 1/4 wavelength transmission line present to a generator when the line is shorted at the far end?

Very high impedance

Very low impedance

The same as the characteristic impedance of the transmission line

The same as the generator output impedance



2016-E9F14: What impedance does a 1/2 wavelength transmission line present to a generator when the line is shorted at the far end?

Very low impedance

Very high impedance

The same as the characteristic impedance of the line

The same as the output impedance of the generator



2016-E9F15: What impedance does a 1/2 wavelength transmission line present to a generator when the line is open at the far end?

Very high impedance

Very low impedance

The same as the characteristic impedance of the line

The same as the output impedance of the generator



2016-E9F16: Which of the following is a significant difference between foam dielectric coaxial cable and solid dielectric cable, assuming all other parameters are the same?

All of these choices are correct

Foam dielectric has lower safe operating voltage limits

Foam dielectric has lower loss per unit of length

Foam dielectric has higher velocity factor





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2016-E9E: Matching: matching antennas to feed lines; phasing lines; power dividers
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