GROL Antennas and Transmission Lines 2

Question 1

What does a standing wave ratio (SWR) of 1:1 indicate on a transmission line?

Accepted Answer

Perfect impedance match with maximum power transfer and no reflected power

Answer

Total reflection of power at the antenna feedpoint

Answer

Half of the transmitted power is reflected back to the transmitter

Answer

The transmission line is open-circuited at the antenna end

Question 2

What is the characteristic impedance of coaxial cable most commonly used in commercial radio transmitter installations?

Accepted Answer

50 ohms

Answer

25 ohms

Answer

300 ohms

Answer

600 ohms

Question 3

What happens to RF power when there is an impedance mismatch between a transmission line and an antenna?

Accepted Answer

Standing waves are created and some power is reflected back toward the transmitter

Answer

All power is dissipated as heat in the cable dielectric

Answer

The antenna radiates more power than was delivered to the feedline

Answer

The operating frequency shifts to compensate for the mismatch

Question 4

What is the velocity factor of a transmission line?

Accepted Answer

The ratio of signal propagation speed in the line to the speed of light in free space

Answer

The ratio of transmitted power to reflected power on the line

Answer

The frequency at which the transmission line is exactly one wavelength long

Answer

The maximum RF current the line can safely carry

Question 5

What is the primary risk of operating a transmitter into a high SWR load?

Accepted Answer

Excessive reflected power can overheat and damage the transmitter's final amplifier

Answer

The output frequency increases beyond the licensed bandwidth

Answer

The transmission line radiates RF energy, causing interference

Answer

The antenna gain doubles, causing overmodulation

Question 6

An antenna tuner (matching network) is primarily used to:

Accepted Answer

Transform the antenna impedance to match the transmission line and transmitter output

Answer

Change the resonant frequency of the antenna element

Answer

Amplify the RF signal before it reaches the antenna

Answer

Suppress harmonics radiated by the antenna

Question 7

Which transmission line type generally offers the lowest attenuation per unit length at UHF frequencies for high-power commercial use?

Accepted Answer

Rigid coaxial line or waveguide

Answer

RG-58/U flexible coaxial cable

Answer

RG-8/U coaxial cable

Answer

Open-wire parallel feedline (ladder line)