HAM HAM Radio Extra Class Test Antenna Theory and Design Questions and Answers 2

Question 1

What is the approximate radiation resistance of a half-wave dipole antenna in free space?

Accepted Answer

73 ohms

Answer

A half-wave dipole in free space has a theoretical radiation resistance of approximately 73 ohms.

Question 2

What type of antenna pattern does a collinear array produce?

Accepted Answer

Omnidirectional with gain concentrated at low elevation angles

Answer

A collinear array stacks radiating elements vertically to compress radiation toward the horizon, producing omnidirectional coverage with low-angle gain.

Question 3

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

Accepted Answer

Wide bandwidth with relatively constant gain and impedance

Answer

The LPDA provides consistent gain and impedance characteristics across a wide frequency range due to its scaled element design.

Question 4

How does the beamwidth of a parabolic dish antenna change as the dish diameter increases relative to wavelength?

Accepted Answer

Beamwidth decreases

Answer

A larger dish diameter relative to wavelength produces a narrower beamwidth and higher gain.

Question 5

What is the effect of adding a reflector element to a Yagi-Uda antenna?

Accepted Answer

It increases forward gain and improves the front-to-back ratio

Answer

A reflector element directs energy forward, increasing gain and reducing radiation off the back of the antenna.

HAM - Radio Extra Class Test Practice Test

HAM - Radio Extra Class Test Practice Test

HAM HAM Radio Extra Class Test Antenna Theory and Design Questions and Answers 2