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

Question 1

A Yagi antenna is designed for the 2-meter band.
If the director elements are slightly shorter than the driven element, and the reflector is slightly longer, what is the primary effect of these length differences?

Accepted Answer

To create a directional radiation pattern with forward gain.

Answer

To increase the antenna's bandwidth.

Answer

To decrease the SWR on the feed line.

Answer

To enable multi-band operation.

Question 2

An amateur radio operator is setting up a satellite communication link. Which type of antenna polarization is most advantageous to mitigate signal fading due to the satellite's rotation and changing orientation?

Accepted Answer

Circular polarization

Answer

Horizontal polarization

Answer

Vertical polarization

Answer

Slant polarization

Question 3

What is the theoretical free-space radiation resistance at the feed point of a center-fed half-wave dipole antenna?

Accepted Answer

73 ohms

Answer

50 ohms

Answer

300 ohms

Answer

600 ohms

Question 4

In antenna theory, what distinguishes the far-field region from the near-field region?

Accepted Answer

The antenna's radiation pattern is independent of distance in the far-field region.

Answer

The far-field is where the E and H fields are in phase, while in the near-field they are 180 degrees out of phase.

Answer

The near-field region is dominated by radiated power, while the far-field is dominated by reactive power.

Answer

Impedance measurements are only valid in the near-field region.

Question 5

A radio operator uses an antenna tuner to match a non-resonant antenna to a 50-ohm transmitter. Which statement accurately describes the effect of the tuner?

Accepted Answer

The tuner presents a 50-ohm load to the transmitter, improving power transfer from the radio.

Answer

The tuner physically alters the antenna's length to make it resonant.

Answer

The tuner eliminates all power loss in the feed line.

Answer

The tuner corrects the SWR on the feed line between the tuner and the antenna.

Question 6

If a 100-foot length of coaxial cable with a velocity factor of 0.66 is used to construct a quarter-wave matching stub at 14.1 MHz, what is its approximate physical length?

Accepted Answer

The type of dielectric material used between the conductors

Answer

The conductivity of the center conductor and shield

Answer

The overall diameter of the cable

Answer

The frequency of the signal being transmitted

A Yagi antenna is designed for the 2-meter band.If the director elements are slightly shorter than the driven element, and the reflector is slightly longer, what is the primary effect of these length differences?

A Yagi antenna is designed for the 2-meter band.
If the director elements are slightly shorter than the driven element, and the reflector is slightly longer, what is the primary effect of these length differences?