What describes an isotropic antenna?
- A grounded antenna used to measure earth conductivity
- A horizontally polarized antenna used to compare Yagi antennas
- A theoretical antenna used as a reference for antenna gain
- A spacecraft antenna used to direct signals toward the earth
What antenna has no gain in any direction?
- Quarter-wave vertical
- Half-wave dipole
- Isotropic antenna
Why would one need to know the feed point impedance of an antenna?
- To match impedances in order to minimize standing wave ratio on the transmission line
- To measure the near-field radiation density from a transmitting antenna
- To calculate the front-to-side ratio of the antenna
- To calculate the front-to-back ratio of the antenna
Which of the following factors may affect the feed point impedance of an antenna?
- Transmission-line length
- Antenna height, conductor length/diameter ratio and location of nearby conductive objects
- The settings of an antenna tuner at the transmitter
- Sunspot activity and time of day
What is included in the total resistance of an antenna system?
- Radiation resistance plus space impedance
- Radiation resistance plus transmission resistance
- Transmission-line resistance plus radiation resistance
- Radiation resistance plus ohmic resistance
How does the beamwidth of an antenna vary as the gain is increased?
- It increases geometrically
- It increases arithmetically
- It is essentially unaffected
- It decreases
What is meant by antenna gain?
- The ratio of the radiated signal strength of an antenna in the direction of maximum radiation to that of a reference antenna
- The ratio of the signal in the forward direction to that in the opposite direction
- The ratio of the amount of power radiated by an antenna compared to the transmitter output power
- The final amplifier gain minus the transmission line losses
What is meant by antenna bandwidth?
- Antenna length divided by the number of elements
- The frequency range over which an antenna satisfies a performance requirement
- The angle between the half-power radiation points
- The angle formed between two imaginary lines drawn through the element ends
How is antenna efficiency calculated?
- (radiation resistance / transmission resistance) x 100 percent
- (radiation resistance / total resistance) x 100 percent
- (total resistance / radiation resistance) x 100 percent
- (effective radiated power / transmitter output) x 100 percent
Which of the following choices is a way to improve the efficiency of a ground-mounted quarter-wave vertical antenna?
- Install a good radial system
- Isolate the coax shield from ground
- Shorten the radiating element
- Reduce the diameter of the radiating element
Which of the following factors determines ground losses for a ground-mounted vertical antenna operating in the 3 MHz to 30 MHz range?
- The standing wave ratio
- Distance from the transmitter
- Soil conductivity
- Take-off angle
How much gain does an antenna have compared to a 1/2-wavelength dipole when it has 6 dB gain over an isotropic antenna?
- 3.85 dB
- 6.0 dB
- 8.15 dB
- 2.79 dB
How much gain does an antenna have compared to a 1/2-wavelength dipole when it has 12 dB gain over an isotropic antenna?
- 6.17 dB
- 9.85 dB
- 12.5 dB
- 14.15 dB
What is meant by the radiation resistance of an antenna?
- The combined losses of the antenna elements and feed line
- The specific impedance of the antenna
- The value of a resistance that would dissipate the same amount of power as that radiated from an antenna
- The resistance in the atmosphere that an antenna must overcome to be able to radiate a signal
What is the effective radiated power relative to a dipole of a repeater station with 150 watts transmitter power output, 2 dB feed line loss, 2.2 dB duplexer loss, and 7 dBd antenna gain?
- 1977 watts
- 78.7 watts
- 420 watts
- 286 watts
What is the effective radiated power relative to a dipole of a repeater station with 200 watts transmitter power output, 4 dB feed line loss, 3.2 dB duplexer loss, 0.8 dB circulator loss, and 10 dBd antenna gain?
- 317 watts
- 2000 watts
- 126 watts
- 300 watts
What is the effective radiated power of a repeater station with 200 watts transmitter power output, 2 dB feed line loss, 2.8 dB duplexer loss, 1.2 dB circulator loss, and 7 dBi antenna gain?
- 159 watts
- 252 watts
- 632 watts
- 63.2 watts
What term describes station output, taking into account all gains and losses?
- Power factor
- Half-power bandwidth
- Effective radiated power
- Apparent power