HAM Antennas and Feed Lines 5

Question 1

What is the radiation pattern of an isotropic antenna?

Accepted Answer

A perfect sphere — equal radiation in all directions

Answer

An isotropic antenna is a theoretical point source that radiates equally in all directions, forming a perfect sphere.

Question 2

What is the significance of the 1:1 SWR condition on a transmission line?

Accepted Answer

Maximum power transfer occurs with no reflected wave

Answer

A 1:1 SWR means the line is perfectly matched — all forward power is absorbed by the load with no reflection.

Question 3

A log-periodic dipole array (LPDA) antenna is best described as:

Accepted Answer

A broadband directional antenna with moderate gain across a wide frequency range

Answer

An LPDA is a broadband directional antenna providing consistent moderate gain across a wide frequency range, widely used for HF communication.

Question 4

What is the effect of ground conductivity on the performance of a quarter-wave vertical antenna with radials?

Accepted Answer

Higher conductivity reduces ground losses and improves radiation efficiency

Answer

Higher ground conductivity reduces the resistive loss in the ground return current path, improving the efficiency and gain of a vertical antenna.

Question 5

What is the advantage of using a terminated folded dipole (T2FD) antenna?

Accepted Answer

Broadband operation with low SWR across a wide frequency range due to the terminating resistor

Answer

The T2FD uses a terminating resistor to achieve a broad, low-SWR frequency range at the expense of efficiency, making it useful for wideband receive or transmit applications.

HAM - Radio Extra Class Test Practice Test

HAM - Radio Extra Class Test Practice Test

HAM Antennas and Feed Lines 5