HAM Antenna Theory and Design 3

Question 1

What is the purpose of a loading coil in an electrically short antenna?

Accepted Answer

To resonate the antenna by canceling the capacitive reactance

Answer

A loading coil adds inductive reactance to cancel the capacitive reactance of an electrically short antenna, bringing it to resonance.

Question 2

What is the gain of a large parabolic dish antenna primarily determined by?

Accepted Answer

The diameter of the dish relative to the wavelength

Answer

The gain of a parabolic dish is primarily determined by the ratio of the dish diameter to the operating wavelength.

Question 3

What is an NVIS (Near Vertical Incidence Skywave) antenna optimized for?

Accepted Answer

Local and regional communications within about 300 miles

Answer

An NVIS antenna radiates at very high angles (near vertical) to use the ionosphere for regional communications within approximately 300 miles.

Question 4

What is the characteristic of an antenna with a very high Q factor?

Accepted Answer

Narrow bandwidth and high efficiency for a resonant antenna

Answer

A high-Q antenna has a narrow bandwidth, meaning it is very frequency-selective and operates efficiently only over a small frequency range.

Question 5

Which of the following describes an end-fire antenna array?

Accepted Answer

Maximum radiation is along the axis of the array

Answer

An end-fire array produces maximum radiation along the axis of the array, like a Yagi antenna.

HAM - Radio Extra Class Test Practice Test