RF Cafe Quiz #16

All RF Cafe quizzes would make perfect fodder for employment interviews for technicians or engineers - particularly those who are fresh out of school or are relatively new to the work world. Come to think of it, they would make equally excellent study material for the same persons who are going to be interviewed for a job.

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Note: Many answers contain passages quoted in whole or in part from the text.

1. What does dBi, the most often used unit for antenna gain (or directivity), stand for?

a) Decibels of isolation
b) Isometric radiation in decibels
c) Decibels of gain relative to an isotropic radiator
d) Intrinsic gain in decibels

2. For which region of space does antenna gain normally apply?

a) Near field
b) Far field
c) At the feed point
d) Everywhere

antenna coordinates and radiation pattern  antenna coordinates and radiation pattern
  Elevation Pattern         Azimuth Pattern
3. For which type of antenna does the pattern to the right describe?

a) Parabolic
b) Yagi
c) 1/2-wave dipole
d) 1/4-wave vertical whip

4. What is the free space impedance that an antenna "sees?"

a) 50 Ω
b) 75 Ω
c) 16p Ω (≈50 Ω)
d) 120p Ω (≈377 Ω)

5. What is the name given to the point where the RF input signal interfaces to the antenna?

a) ICP (input connection point)
b) Feed-point
c) BNC connector
d) N connector

6. Where is the approximate transition point between near field and far field?

a) λ / (2p)
b) λ
c) 5λ
d) 10λ

7. What is an isotropic radiator?

a) An antenna that radiates equally in all directions
b) An antenna with equal dimensions
c) An antenna designed to broadcast in the troposphere
d) None of the above

8. Which type of antenna would typically have the highest directivity?

a) 1/4-wave whip
b) Folded dipole
c) Yagi
d) Parabolic

9. On a center-fed 1/2-wave dipole, where is the voltage potential the highest?

a) In the center
b) At the tips
c) Equal everywhere
d) Nowhere - dipoles operate on current

10. Yagi antennas are constructed of which three types of elements?

a) Transmitter, receiver, and transceiver
b) Underdriven, driven, and overdriven
c) Reflector, driven, and director
d) Aluminum, iron, and magnesium

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