HAM FREE HAM Radio Extra Class Test Antennas and Feed Lines Questions and Answers 3

Question 1

What is the effect of ground conductivity on the radiation pattern of a vertically polarized antenna?

Accepted Answer

Better ground conductivity improves low-angle radiation

Answer

Better ground conductivity raises the takeoff angle

Answer

Ground conductivity has no effect on vertical antennas

Answer

Poor ground conductivity improves low-angle radiation

Question 2

What is the characteristic impedance of standard window line (twin-lead) commonly used in amateur radio?

Accepted Answer

300 ohms

Answer

75 ohms

Answer

50 ohms

Answer

450 ohms

Question 3

Which of the following best describes the radiation pattern of a two-element Yagi antenna?

Accepted Answer

A cardioid pattern with maximum radiation toward the director

Answer

An omnidirectional pattern in the horizontal plane

Answer

A figure-eight pattern broadside to the elements

Answer

Equal radiation in all directions including vertical

Question 4

What is the total loss in a feed line system if the matched-line loss is 2 dB and the SWR at the load is 3:1?

Accepted Answer

Greater than 2 dB due to additional SWR-related loss

Answer

Exactly 2 dB regardless of SWR

Answer

Less than 2 dB because SWR reduces loss

Answer

Zero because the SWR cancels the matched loss

Question 5

What is the approximate gain of a five-element Yagi antenna over a dipole?

Accepted Answer

Approximately 10 dBd

Answer

Approximately 3 dBd

Answer

Approximately 20 dBd

Answer

Approximately 1 dBd

Question 6

Why is it important to seal the end of coaxial cable exposed to weather?

Accepted Answer

To prevent moisture ingress that increases line loss

Answer

To increase the velocity factor of the cable

Answer

To prevent RF leakage from the open end

Answer

To maintain the cable's characteristic impedance at DC