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

Higher ground conductivity enhances low-angle radiation from vertical antennas, which is desirable for DX communications.

Question 2

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

Accepted Answer

300 ohms

Answer

Standard TV-type window line (twin-lead) has a characteristic impedance of 300 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

A two-element Yagi produces a cardioid-shaped pattern with the main lobe directed from the reflector toward the director.

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

When SWR is greater than 1:1, the total feed line loss exceeds the matched-line loss because reflected power traverses the lossy line multiple times.

Question 5

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

Accepted Answer

Approximately 10 dBd

Answer

A well-designed five-element Yagi typically provides about 10 dBd of gain over a reference dipole.

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