Ham Radio General Class Test FREE Ham Radio General Class Test Antennas and Feed Lines Questions and Answers 2

Question 1

What is the approximate length of a quarter-wave vertical antenna for 14.2 MHz?

Accepted Answer

16.5 feet

Answer

A quarter-wave antenna length is calculated as 234 divided by the frequency in MHz, giving approximately 16.5 feet for 14.2 MHz.

Question 2

What type of feed line loss increases significantly when the line is operated with high SWR?

Accepted Answer

Coaxial cable

Answer

Coaxial cable losses increase dramatically under high SWR conditions compared to open-wire feed lines.

Question 3

What is the primary advantage of a log-periodic dipole array (LPDA) antenna?

Accepted Answer

Wide bandwidth with consistent gain and impedance

Answer

An LPDA provides relatively constant gain and impedance characteristics across a wide frequency range.

Question 4

What happens to the feed point impedance of a half-wave dipole as it is raised from near ground level to a height of one wavelength?

Accepted Answer

It fluctuates between approximately 50 and 90 ohms

Answer

The feed point impedance of a dipole oscillates as height changes due to ground reflection effects, varying roughly between 50 and 90 ohms.

Question 5

Which of the following describes the velocity factor of a feed line?

Accepted Answer

The speed at which a signal travels through the line compared to the speed of light

Answer

Velocity factor is the ratio of signal propagation speed in the feed line to the speed of light in free space.

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