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# Antennas and Site Engineering for Mobile Radio NetworksAnswers 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, buena suerte, удачи, in bocca al lupo, 행운을 빕니다, ádh mór, בהצלחה, lykke til, 祝你好運. Well, you know what I mean: Good luck!

Note: Some material based on books have quoted passages.

This quiz is based on the information presented in Antennas and Site Engineering for Mobile Radio Networks, by Bruno Delorme.

rtech 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 m and m'?

c)  Two electric charges

Two electric charges.  Two electric charges, m and m', 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 propagation?

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

The 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.

b)  λ 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 page 155)

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