E9C Phased vertical antennas; radiation
patterns; beverage antennas;
rhombic antennas: resonant; nonresonant; radiation pattern; antenna
patterns: elevation above real ground, ground effects as related to
polarization, take-off angles as a function of height above ground
E9C01
(D)
What is
the radiation pattern of two 1/4-wavelength vertical antennas spaced
1/2-wavelength apart and fed 180 degrees out of phase?
A. Unidirectional cardioid
B. Omnidirectional
C. Figure-8 broadside to the antennas
D. Figure-8 end-fire in line
with the antennas
E9C02
(A)
What is
the radiation pattern of two 1/4-wavelength vertical antennas spaced
1/4-wavelength apart and fed 90 degrees out of phase?
A. Unidirectional cardioid
B. Figure-8 end-fire
C. Figure-8 broadside
D. Omnidirectional
E9C03
(C)
What is
the radiation pattern of two 1/4-wavelength vertical antennas spaced
1/2-wavelength apart and fed in phase?
A. Omnidirectional
B. Cardioid unidirectional
C. Figure-8 broadside to the
antennas
D. Figure-8 end-fire in line with the antennas
E9C04
(D)
What is
the radiation pattern of two 1/4-wavelength vertical antennas spaced
1/4-wavelength apart and fed 180 degrees out of phase?
A. Omnidirectional
B. Cardioid unidirectional
C. Figure-8 broadside to the antennas
D. Figure-8 end-fire in line
with the antennas
E9C05
(D)
What is
the radiation pattern for two 1/4-wavelength vertical antennas spaced
1/8-wavelength apart and fed 180 degrees out of phase?
A. Omnidirectional
B. Cardioid unidirectional
C. Figure-8 broadside to the antennas
D. Figure-8 end-fire in line
with the antennas
E9C06
(B)
What is
the radiation pattern for two 1/4-wavelength vertical antennas spaced
1/4-wavelength apart and fed in phase?
A. Substantially unidirectional
B. Elliptical
C. Cardioid unidirectional
D. Figure-8 end-fire in line with the antennas
E9C07
(B)
Which
of the following is the best description of a resonant rhombic antenna?
A. Unidirectional; four-sided, each side a
half-wavelength long; terminated in a resistance equal to its characteristic
impedance
B. Bidirectional;
four-sided, each side approximately one wavelength long; open at the end
opposite the transmission line connection
C. Four-sided; an LC network at each vertex
except for the transmission connection; tuned to resonate at the operating
frequency
D. Four-sided, each side of a different
physical length; traps at each vertex for changing resonance according to band
usage
E9C08
(A)
What
are the advantages of a nonresonant rhombic antenna?
A. Wide frequency range,
high gain and high front-to-back ratio
B. High front-to-back ratio, compact size and
high gain
C. Unidirectional radiation pattern, high gain
and compact size
D. Bidirectional radiation pattern, high gain
and wide frequency range
E9C09
(C)
What
are the disadvantages of a nonresonant rhombic antenna?
A. A large area for proper installation and a
narrow bandwidth
B. A large area for proper installation and a
low front-to-back ratio
C. A large area and four
sturdy supports for proper installation
D. A large amount of aluminum tubing and a low
front-to-back ratio
E9C10
(B)
What is
the effect of a terminating resistor on a rhombic antenna?
A. It reflects the standing waves on the
antenna elements back to the transmitter
B. It changes the radiation
pattern from essentially bidirectional to essentially unidirectional
C. It changes the radiation pattern from
horizontal to vertical polarization
D. It decreases the ground loss
E9C11
(A)
What
type of antenna pattern over real ground is shown in Figure A9-2?
A. Elevation pattern
B. Azimuth pattern
C. E-Plane pattern
D. Polarization pattern
E9C12
(D)
How is
the far-field elevation pattern of a vertically polarized antenna affected by
being mounted over seawater versus rocky ground?
A. The low-angle radiation decreases
B. The high-angle radiation increases
C. Both the high- and low-angle radiation
decrease
D. The low-angle radiation
increases
E9C13
(C)
If only
a modest on-ground radial system can be used with an eighth-wavelength-high,
inductively loaded vertical antenna, what would be the best compromise to
minimize near-field losses?
A. 4 radial wires, 1 wavelength long
B. 8 radial wires, a half-wavelength long
C. A wire-mesh screen at the
antenna base, an eighth-wavelength square
D. 4 radial wires, 2 wavelengths long
E9C14
(C)
In the
antenna radiation pattern shown in Figure A9-2, what is the elevation angle of
the peak response?
A. 45 degrees
B. 75 degrees
C. 7.5 degrees
D. 25 degrees
E9C15
(B)
In the
antenna radiation pattern shown in Figure A9-2, what is the front-to-back
ratio?
A. 15 dB
B. 28 dB
C. 3 dB
D. 24 dB
E9C16
(D)
What is
one characteristic of a Beverage antenna?
A. For best performance it must not exceed 1/4
wavelength in length at the desired frequency
B. For best performance it must be mounted more
than 1 wavelength above ground at the desired frequency
C. For best performance it should be configured
as four-sided loop
D. For best performance it
should be as long as possible