This is the Multiple Choice Questions in Chapter 16: Antenna from the book Electronic Communication Systems by Roy Blake
Start Practice Exam Test Questions
Choose the letter of the best answer in each questions.
MULTIPLE CHOICE
1. The real part of an antenna's input impedance is due to:
- a. the radiated signal
- b. the reflected signal
- c. the SWR
- d. all of the above
ANS: A
2. A half-wave dipole is sometimes called:
- a. a Marconi antenna
- b. a Hertz antenna
- c. a Yagi antenna
- d. none of the above
ANS: B
3. The end-to-end length of a half-wave dipole antenna is actually:
- a. one wavelength
- b. one half-wavelength
- c. slightly longer than a half-wavelength
- d. slightly shorter than a half-wavelength
ANS: D
4. The radiation of energy from an antenna can be seen in the:
- a. standing wave pattern around the antenna
- b. SWR along the feed cable
- c. radiation resistance of the antenna
- d. I2R loss of the antenna
ANS: C
5. Measured on the ground, the field strength of a horizontally polarized half-wave dipole antenna is
strongest:
- a. in one direction
- b. in two directions
- c. in all directions
- d. depends on the number of elements
ANS: B
6. The ability of an antenna to radiate more energy in one direction than in other directions is called:
- a. directivity
- b. selectivity
- c. active antenna
- d. resonance
ANS: A
7. The front-to-back ratio of a half-wave dipole antenna is:
- a. 0 dB
- b. 3 dB
- c. 10 dB
- d. infinite
ANS: A
8. An antenna's beamwidth is measured:
- a. from +90° to –90°
- b. from front to back
- c. between half-power points
- d. between the minor side-lobes
ANS: C
9. ERP stands for:
- a. Equivalent Radiation Pattern
- b. Effective Radiation Pattern
- c. Equivalent Radiated Power
- d. Effective Radiated Power
ANS: D
10. "Ground Effects" refers to the effects on an antenna's radiation pattern caused by:
- a. radio signals reflecting off the ground
- b. buildings and other structures on the ground
- c. fading
- d. faulty connection of the feed cable ground
ANS: A
11. A 1-MHz monopole antenna must be:
- a. mounted vertically
- b. mounted horizontally
- c. at least one half-wavelength long
- d. at least one wavelength long
ANS: A
12. The typical antenna in an AM radio is a:
- a. dipole
- b. folded dipole
- c. ferrite "loop-stick"
- d. none of the above
ANS: C
13. The polarization of plane waves received from a satellite is changed by:
- a. gamma rays
- b. Faraday Rotation
- c. helical rotation
- d. the distance traveled
ANS: B
14. A nonresonant antenna:
- a. will not transmit
- b. will not receive
- c. will cause SWR on the feed cable
- d. all of the above
ANS: C
15. At resonance, the input impedance to a lossless antenna should be:
- a. resistive
- b. inductive
- c. capacitive
- d. infinite
ANS: A
16. An antenna can be matched to a feed line using:
- a. a shorted stub
- b. a loading coil
- c. an LC network
- d. all of the above
ANS: D
17. As the length of a "long-wire" antenna is increased:
- a. the number of lobes increases
- b. the number of nodes decreases
- c. efficiency decreases
- d. none of the above
ANS: A
18. Arrays can be:
- a. phased
- b. driven
- c. parasitic
- d. all of the above
ANS: D
19. An array with one driven element, a reflector, and one or more directors is called a:
- a. Marconi
- b. Yagi
- c. Log-Periodic Dipole
- d. stacked array
ANS: B
20. LPDA stands for:
- a. Low-Power Dipole Array
- b. Low-Power Directed Array
- c. Log-Periodic Dipole Array
- d. Log Power Dipole Array
ANS: C
21. The radiated beam from a parabolic "dish" transmitting antenna is:
- a. collimated
- b. phased
- c. dispersed
- d. none of the above
ANS: A
22. The energy picked up by a parabolic antenna is concentrated at the:
- a. center
- b. edges
- c. focus
- d. horn
ANS: C
23. Antennas are often tested in:
- a. an echo chamber
- b. an anechoic chamber
- c. a vacuum chamber
- d. an RF reflective chamber
ANS: B
24. Field strength at a distance from an antenna is measured with:
- a. a slotted line
- b. a dipole
- c. an EIRP meter
- d. a field-strength meter
ANS: D
COMPLETION
1. An antenna is the interface between the transmission line and ____________________.
ANS: space
2. Hertz antenna is another name for a half-wave ____________________.
ANS: dipole
3. The length of a half-wave dipole is about ____________________ % of a half-wave in free space.
ANS: 95
4. The ____________________ resistance is the portion of an antenna's input impedance due to transmitted radio waves leaving the antenna.
ANS: radiation
5. Input impedance at the center feed point of a resonant half-wave dipole is about ____________________ W.
ANS: 70
6. Input impedance at the center feed point of a resonant folded dipole is about ____________________ W.
ANS: 280 – 300
7. The vertical angle of radiation is called the angle of ____________________.
ANS: elevation
8. Antenna radiation patterns are typically drawn on graphs with ____________________ coordinates.
ANS: polar
9. As compared to a ____________________ source, a half-wave dipole has a gain of about 2 dBi.
ANS:
point
isotropic
10. Antenna gain measured in ____________________ is with reference to a half-wave dipole.
ANS: dBd
11. ____________________ is the same as the gain for a lossless antenna.
ANS: Directivity
12. The front-to-back ratio of a half-wave dipole is ____________________ dB.
ANS: 0
13. The ____________________ of a directional antenna is the angle between its half-power points.
ANS: beamwidth
14. ERP stands for ____________________ radiated power.
ANS: effective
15. ERP is the power input to the antenna multiplied by the antenna's ____________________.
ANS: gain
16. A ____________________ is required to connect a coaxial cable to a center-fed dipole antenna.
ANS: balun
17. A horizontally mounted dipole will radiate waves with ____________________ polarization.
ANS: horizontal
18. A folded dipole has ____________________ bandwidth than a standard dipole.
ANS:
wider
greater
more
19. A monopole antenna is typically mounted in the ____________________ direction.
ANS: vertical
20. The length of a typical monopole antenna is ____________________ wavelength.
ANS:
one-quarter
1/4
21. A monopole antenna mounted high on a tower typically uses a ____________________ plane.
ANS: ground
22. A vertical antenna has an _________________________ radiation pattern for ground-based receivers.
ANS: omnidirectional
23. The number of driven elements in a Yagi antenna is typically ____________________.
ANS: one
24. The reflector on a Yagi antenna is called a ____________________ element.
ANS: parasitic
25. An LPDA is a ____________________ dipole array.
ANS: log-periodic
26. If an LPDA had five elements, the number of driven elements it had would be ____________________.
ANS: five
27. All the waves that hit the surface of a parabolic antenna merge at the ____________________.
ANS: focus
28. A ____________________ beam has all its individual rays parallel to each other.
ANS: collimated
29. A microwave ____________________ antenna is essentially an extension of a waveguide.
ANS: horn
30. An ____________________ chamber is often used to test microwave antennas.
ANS: anechoic
SHORT ANSWER
1. Calculate the physical length of a half-wave dipole for use at 300 MHz.
ANS:
475 millimeters
2. How much power will a 95% efficient antenna radiate if driven with 100 watts?
ANS:
95 watts
3. If an antenna has 10.14 dB of gain compared to a point source, how much gain does it have compared to a half-wave dipole?
ANS:
8 dB
4. What is the ERP of an antenna with 10 dBd of gain and driven by one watt?
ANS:
10 watts
5. A resonant antenna has an input impedance of 100 ohms and is driven by 100 watts. What is the RMS current in the antenna?
ANS:
1 ampere
6. A resonant antenna has an input impedance of 100 ohms and is driven by 100 watts. What is the RMS voltage at the feed-point of the antenna?
ANS:
100 volts
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