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Return to RF Cafe Quiz #40
quiz is based on the information presented in Introduction to Antenna Analysis Using EM Simulation, by
Hiroaki Kogure, Yoshie Kogure, and James C. Rautio. This book is also a great source of antenna fundamentals and a
little communications history.
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1. What was the
James C. Ratio's first antenna design program?
"The programs I wrote for those QST articles,
called "Annie," is what got my company started. (see page xiii)
2. Just exactly
is an antenna?
c) Any structure that performs the function of transmitting and receiving electromagnetic
An antenna is usually made from metal pipe, conducting wire, or metal traces on a PCB. (see page 3)
3. Where is the approximate location of the near field / far field transition?
c) λ from the
Up to about one wavelength around the antenna is called the near field. (see page 29)
4. What does a time-varying magnetic field generate?
a) An electric field
Faraday's law of induction, described in Chapter 1, states that "a time varying
magnetic field generates an electric field." (see page 53)
5. What is the
impedance of a minimum-loss coaxial cable with an air dielectric?
c) 75 Ω
When coax uses an air
dielectric, we see minimum loss in the cable when we choose its dimensions so that the characteristic impedance (Z0)
is about 75 ohms. When the coax is filled with a dielectric of relative permittivity of 2.55 (say, polyethylene),
the minimum loss dimensions give a Z0 of about 50 ohms. (see page 88)
6. How is dielectric material modeled in an EM simulator?
b) Parallel RC
Dielectric material can be represented as an equivalent parallel RC circuit. The capacitor represents a lossless
dielectric and the resistor represents dielectric loss. (see page 131)
happens to magnetic flux if current through the loop is doubled?
a) It also doubles
Φ (flux) = L
(inductance) * I (current). (see page 165)
8. For an input power of 1 W, what is
the output power of a lossless passive antenna with a specified gain of 3 dB or 6 dB?
b) 1 W for
An antenna with gain outputs more power in one direction and less power in another. If we look at
the total power radiated in all directions, no extra power is created. (see page 200)
Where does a log-periodic antenna get its name?
d) From the logarithmic spacing and length ratios of its
A log-periodic antenna has different length dipoles whose spacings and lengths are determined by means
of the logarithmic function. (see page 229)
10. Proper test environments are
crucial to reliable EM field measurements as evidenced by what factor in Heinrich Hertz's early experiments?
d) A nearby pot-bellied stove
Hertz initially measured a wildly incorrect value for the speed of light in
one of his early experiments. It turns out that the problem was a large cast iron stove located nearby in his
laboratory. Effects of objects of any kind, including walls, earth, concrete, people, and so forth, can seriously
disrupt measurements. (see page 203)
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