2016-E9A: Basic Antenna parameters: radiation resistance, gain, beamwidth, efficiency, beamwidth; effective radiated power, polarization
What describes an isotropic antenna?
A theoretical antenna used as a reference for antenna gain
A grounded antenna used to measure earth conductivity
A horizontally polarized antenna used to compare Yagi antennas
A spacecraft antenna used to direct signals toward the earth
What antenna has no gain in any direction?
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?
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 ohmic resistance
Radiation resistance plus space impedance
Radiation resistance plus transmission resistance
Transmission-line resistance plus radiation resistance
How does the beamwidth of an antenna vary as the gain is increased?
It increases geometrically
It increases arithmetically
It is essentially unaffected
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?
The frequency range over which an antenna satisfies a performance requirement
Antenna length divided by the number of elements
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 / total resistance) x 100 per cent
(radiation resistance / transmission resistance) x 100 per cent
(total resistance / radiation resistance) x 100 per cent
(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
How much gain does an antenna have compared to a 1/2-wavelength dipole when it has 6 dB gain over an isotropic antenna?
How much gain does an antenna have compared to a 1/2-wavelength dipole when it has 12 dB gain over an isotropic antenna?
What is meant by the radiation resistance of an antenna?
The value of a resistance that would dissipate the same amount of power as that radiated from an antenna
The combined losses of the antenna elements and feed line
The specific impedance of the 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?
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?
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?
What term describes station output, taking into account all gains and losses?
Effective radiated power
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