# Extra Class Exam Question Pool

effective 7/01/2008 thru 6/30/2012

 Show: Unseen questions Weak questions Review questions Learned questions Incorrect answer choices

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

 Color key: ● = Unseen ● = Weak ● = Review ● = Learned ● = Incorrect answer
 Previous group:E9E: Matching: matching antennas to feed lines; power dividers Back to index:Extra Class Exam Question Pool Next group:E9G: The Smith chart
Home     What is ham radio?     Which exam to take?     Study tips     Where to take the exam?     Frequently Asked Questions (FAQ)     How to     How much math?     Trouble with practice exams     Feedback     Prices     Free Extra course for active volunteer examiners     Refund policy     Terms and conditions     Bumper sticker     Advertise with us     The Ham band     Rate us     Question pools     Course structure     Survivalists     Documents     facebook     Google+     Contact us     May Day Ham Radio!     Christina's story     TestOnline     Links