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; transformation characteristics of line terminated in impedance not equal to characteristic impedance
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
E9F02:
What determines the velocity factor in a transmission line?
Dielectric materials used in the line
The termination impedance
The line length
The center conductor resistivity
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
E9F04:
What is the typical velocity factor for a coaxial cable with solid polyethylene dielectric?
0.66
2.70
0.30
0.10
E9F05:
What is the physical length of a coaxial transmission line that is electrically one-quarter wavelength long at 14.1 MHz? (Assume a velocity factor of 0.66.)
3.5 meters
20 meters
2.3 meters
0.2 meters
E9F06:
What is the physical length of a parallel conductor feed line that is electrically one-half wavelength long at 14.10 MHz? (Assume a velocity factor of 0.95.)
10 meters
15 meters
20 meters
71 meters
E9F07:
What characteristic will 450-ohm ladder line have at 50 MHz, as compared to 0.195-inch-diameter coaxial cable (such as RG-58)?
Lower loss
Higher SWR
Smaller reflection coefficient
Lower velocity factor
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
E9F09:
What would be the physical length of a typical coaxial transmission line that is electrically one-quarter wavelength long at 7.2 MHz? (Assume a velocity factor of 0.66)
6.9 meters
10 meters
24 meters
50 meters
E9F10:
What kind of 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
E9F11:
What kind of 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
E9F12:
What kind of impedance does a 1/4-wavelength transmission line present to a generator when the line is open at the far end?
A very low impedance
A very high impedance
The same as the characteristic impedance of the line
The same as the input impedance to the final generator stage
E9F13:
What kind of impedance does a 1/4-wavelength transmission line present to a generator when the line is shorted at the far end?
A very high impedance
A very low impedance
The same as the characteristic impedance of the transmission line
The same as the generator output impedance
E9F14:
What kind of impedance does a 1/2-wavelength transmission line present to a generator when the line is shorted at the far end?
A very low impedance
A very high impedance
The same as the characteristic impedance of the line
The same as the output impedance of the generator
E9F15:
What kind of impedance does a 1/2-wavelength transmission line present to a generator when the line is open at the far end?
A very high impedance
A very low impedance
The same as the characteristic impedance of the line
The same as the output impedance of the generator
E9F16:
What is the primary difference between foam-dielectric coaxial cable as opposed to solid-dielectric cable, assuming all other parameters are the same?
All of these answers are correct
Reduced safe operating voltage limits
Reduced losses per unit of length
Higher velocity factor
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