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2016-E9A: Basic Antenna parameters: radiation resistance, gain, beamwidth, efficiency, beamwidth; effective radiated power, polarization

2016-E9A01: 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



2016-E9A02: What antenna has no gain in any direction?

Isotropic antenna

Quarter-wave vertical

Yagi

Half-wave dipole



2016-E9A03: 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



2016-E9A04: 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

Transmission-line length

The settings of an antenna tuner at the transmitter

Sunspot activity and time of day



2016-E9A05: 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



2016-E9A06: How does the beamwidth of an antenna vary as the gain is increased?

It decreases

It increases geometrically

It increases arithmetically

It is essentially unaffected



2016-E9A07: 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



2016-E9A08: 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



2016-E9A09: 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



2016-E9A10: 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



2016-E9A11: Which of the following factors determines ground losses for a ground-mounted vertical antenna operating in the 3 MHz to 30 MHz range?

Soil conductivity

The standing wave ratio

Distance from the transmitter

Take-off angle



2016-E9A12: 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



2016-E9A13: How much gain does an antenna have compared to a 1/2-wavelength dipole when it has 12 dB gain over an isotropic antenna?

9.85 dB

6.17 dB

12.5 dB

14.15 dB



2016-E9A14: 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



2016-E9A15: 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?

286 watts

1977 watts

78.7 watts

420 watts



2016-E9A16: 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



2016-E9A17: 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?

252 watts

159 watts

632 watts

63.2 watts



2016-E9A18: What term describes station output, taking into account all gains and losses?

Effective radiated power

Power factor

Half-power bandwidth

Apparent power





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