GROL - General Radiotelephone Operator License Antennas and Transmission Lines Questions and Answers

Question 1

A technician measures a Standing Wave Ratio (SWR) of 1:1 at the transmitter end of a transmission line. What does this measurement indicate?

Accepted Answer

The impedance of the antenna and transmission line are perfectly matched.

Answer

The transmission line is short-circuited.

Answer

The antenna is not radiating any power.

Answer

The transmission line is acting as an open circuit.

Question 2

Which of the following best describes the polarization of an electromagnetic wave?

Accepted Answer

The orientation of the electric field vector with respect to the Earth's surface.

Answer

The direction of the magnetic field relative to the antenna.

Answer

The ratio of forward power to reflected power.

Answer

The physical length of the antenna's radiating element.

Question 3

What is the approximate theoretical feed-point impedance of a quarter-wavelength vertical antenna (Marconi) when installed with a perfect ground plane system?

Accepted Answer

36 ohms

Answer

50 ohms

Answer

73 ohms

Answer

300 ohms

Question 4

A coaxial cable is specified as having a velocity factor of 0.66. What does this signify?

Accepted Answer

The signal travels through the cable at 66% of the speed of light in a vacuum.

Answer

The cable can only handle 66% of its rated power before overheating.

Answer

The characteristic impedance of the cable is 66 ohms.

Answer

The signal will lose 34% of its strength over 100 feet.

Question 5

What is the primary function of a balun in an RF antenna system?

Accepted Answer

To interface between a balanced system and an unbalanced system.

Answer

To filter out unwanted harmonic frequencies from the transmitter.

Answer

To provide a DC path to ground for static discharge.

Answer

To increase the overall gain of the antenna by focusing the beam.

Question 6

An antenna is specified as having a gain of 3 dBd. What does this mean?

Accepted Answer

The antenna has twice the power gain in its favored direction compared to a half-wave dipole antenna.

Answer

The antenna concentrates its radiated power by a factor of 3 compared to a half-wave dipole antenna.

Answer

The antenna's signal strength is 3 decibels below that of a reference isotropic source.

Answer

The antenna has three times the power gain of an isotropic radiator.