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Answers for RF Cafe Quiz #51
All RF Cafe Quizzes make great 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. Bonne chance, Viel Glück, がんばろう,
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Return to RF Cafe Quiz #51
This quiz is based on the information presented in
Antennas and Site Engineering for Mobile Radio Networks, by Bruno Delorme.
House graciously provided this book.
The book is divided into
three sections: the first section describes the functioning of all types of antennas used in mobile phone networks
and provides examples of each; the second part delves into the engineering of antenna sites, which is crucial to
the quality of mobile networks; the third part of the book includes refresher information on the mathematics and
physics necessary to understand the content of the book and put it to practical use in actual applications. The
book is packed with clear explanations and recommendations for avoiding problems and making the best antenna and
site decisions. Show more Show less
1. In Coulomb's Law, F =
m x m'
/ 4πεr2, what are
c) Two electric charges
Two electric charges. Two electric charges,
exert on each other a force directed along a straight line that joins them and is equal to F. (see page 203)
2. With what phenomenon did James Clerk Maxwell compare electromagnetic wave
a) A stone dropped into a pond
Maxwell compared it with a stone tossed into a pond.
At the point of impact, the stone produces water oscillations, propagating on the surface of the water as waves.
(see page 3)
3. What did Edouard Branly use as the amplification element
of his 'radio conductor' detection device?
c) Iron filings
Branly developed his 'radio conductor'
as a more sensitive detection device. It consisted of a closed circuit that contained a battery, a galvanometer,
and a glass tube containing two pistons face-to-face with iron filings between them. The reception of an electromagnetic
wave decreases the electrical resistance of the filings considerably, causing about a 10x higher current than a
simple resonator. (see page 6)
4. What is the Poynting Vector?
(Wikipedia page for
Poynting Vector animation)
d) The vectorial product of the electric (E)
and magnetic (H) fields at a given point
Poynting vector represents the directional energy flux density (the rate of energy transfer per unit area, in watts
per square meter (W·m-2) of an electromagnetic field.
(see page 13)
5. What is the defining feature of a panel antenna?
a) A conductive panel behind the antenna array for providing directivity
The panel antenna consists
of dipoles aligned vertically according to the same principle as the omnidirectional vertical wire antennas. However,
the dipoles as placed in front of a conductive plane serving as a screen, so as to produce a directive antenna.
(see page 55).
6. Which of the following factors affect the radiation
pattern of an antenna mounted on a pylon or mast?
d) All the above
Directivity is affected by all
three factors. (see page 97)
7. In order to isolate co-located antennas
with vertical polarization, which of the two minimum separation distances are required.
in the vertical, 3λ in the horizontal
Based on mutual impedance calculations, antenna separations of λ in the
vertical and 3λ in the horizontal produces negligible interaction. (see page 93)
8. What are the main sources of noise from transmitter?
a) Harmonic distortion
and oscillator phase noise
The other three choices are not generated from within the transmitter. (see
9. What type of illumination must a parabolic reflector utilize
for proper operation?
c) Spherical wave
The parabolic antenna is illuminated by a spherical wave
provided by a horn placed in the focus of the paraboloid. It provides a plane wave thanks to the property of the
paraboloid. (see page 170)
10. Which governing body is responsible
for worldwide frequency coordination?
d) The International Telecommunications Union
Located in Geneva,
Switzerland, the International Telecommunications Union (ITU) is responsible for worldwide telecommunication activities
(wired and wireless). (see page 189)
Posted July 21, 2013