Libris Britannia 4/science library(b).zip/science library(b)/HAMRADIO/EXT21.ZIP/EXT9.DAT

Text File | 1993-03-09 | 17KB | 444 lines

392I-1A1 A 9-1  Omnidirectional antenna
What is an isotropic radiator?
A. A hypothetical, omnidirectional antenna
B. In the northern hemisphere, an antenna whose directive
   pattern is constant in southern directions
C. An antenna high enough in the air that its directive
   pattern is substantially unaffected by the ground
   beneath it
D. An antenna whose directive pattern is substantially
   unaffected by the spacing of the elements
*
393I-1B1 A 9-1  Comparing gains
When is it useful to refer to an isotropic radiator?
A. When comparing the gains of directional antennas
B. When testing a transmission line for for standing wave ratio
C. When (in the northern hemisphere) directing the transmission
   in a southerly direction
D. When using a dummy load to tune a transmitter
*
394I-1B2 D 9-1  Isotropic
What theoretical reference antenna provides a comparison for
antenna measurements?
A. Quarter-wave vertical
B. Yagi
C. Bobtail curtain
D. Isotropic radiator
*
395I-1B3 B 9-1  Reference for antenna gain
What purpose does an isotropic radiator serve?
A. It is used to compare signal strengths (at a distant
   point) of different transmitters
B. It is used as a reference for antenna gain measurements
C. It is used as a dummy load for tuning transmitters
D. It is used to measure the standing wave-wave-ratio
   on a transmission line
*
396I-1B4 B 9-2  2.1 dB
How much gain does a 1/2-wavelength dipole have over an
isotropic radiator?
A. About 1.5 dB
B. About 2.1 dB
C. About 3.0 dB
D. About 6.0 dB
*
397I-1B5 A 9-2  6 dB - 2.1 dB = 3.9 dB
How much gain does an antenna have over a 1/2-wavelength
dipole when it has 6 dB gain over an isotropic radiator?
A. About 3.9 dB
B. About 6.0 dB
C. About 8.1 dB
D. About 10.0 dB
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398I-1B6 B 9-2  12 dB - 2.1 dB = 9.9 dB
How much gain does an antenna have over a 1/2-wavelength
dipole when it has 12 dB gain over an isotropic radiator?
A. About 6.1 dB
B. About 9.9 dB
C. About 12.0 dB
D. About 14.1 dB
*
399I-1C1 D 9-2  Omnidirectional
What is the antenna pattern for an isotropic radiator?
A. A figure-8
B. A unidirectional cardioid
C. A parabola
D. A sphere
*
400I-1C2 D 9-2  Omnidirectional
What type of directivity pattern does an isotropic radiator
have?
A. A figure-8
B. A unidirectional cardioid
C. A parabola
D. A sphere
*
401I-2A1 D 9-5  Figure-8 end-fire
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
*
402I-2A2 A 9-4  Cardioid
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
*
403I-2A3 C 9-5  Figure-8 broadside
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
*
404I-2A4 C 9-5  1/2 wavelength
How far apart should two 1/4 wavelength vertical antennas
be spaced in order to produce a figure-8 pattern that is
broadside to the plane of the verticals when fed in phase?
A. 1/8 wavelength
B. 1/4 wavelength
C. 1/2 wavelength
D. 1 wavelength
*
405I-2A5 A 9-5  One half wavelength apart
How many 1/2 wavelengths apart should two 1/4 wavelength vertical
antennas be spaced to produce a figure-8 pattern that is in line
with the vertical antennas when they are fed 180 degrees out of
phase?
A. One half wavelength apart
B. Two half wavelengths apart
C. Three half wavelengths apart
D. Four half wavelengths apart
*
406I-2A6 D 9-4  Figure-8 end-fire
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
*
407I-2A7 D 9-4  Figure-8 end-fire
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
*
408I-2A8 A 9-4  Omnidirectional
What is the radiation pattern for two 1/4-wavelength vertical
antennas spaced 1/8 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
*
409I-2A9 B 9-4  Elliptical
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
*
410I-3A1 B 9-6  Bidirectional antenna
What is a resonant rhombic antenna?
A. A unidirectional antenna, each of whose sides is equal to
   half a wavelength and which is terminated in a resistance
   equal to its characteristic impedance
B. A bidirectional antenna open at the end opposite that to
   which the transmission line is connected and with each side
   approximately equal to one wavelength
C. An antenna with an LC network at each vertex (other than
   that to which the transmission line is connected) tuned to
   resonate at the operating frequency
D. A high-frequency antenna, each of whose sides contains
   traps for changing the resonance to match the band in use
*
411I-3B1 A 9-6  Unidirectional antenna terminated in a|resistance equal to its characteristic|impedance, which is about 700 to 800 Ω
What is a nonresonant rhombic antenna?
A. A unidirectional antenna terminated in a resistance equal
   to its characteristic impedance
B. An open-ended bidirectional antenna
C. An antenna resonant at approximately double the frequency
   of the intended band of operation
D. A horizontal triangular antenna consisting of two adjacent
   sides and the long diagonal of a resonant rhombic antenna
*
412I-3B2 A 9-7  Wide frequency range
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
*
413I-3B3 D 9-7  It's big
What are the disadvantages of a nonresonant rhombic antenna?
A. It requires a large area for proper installation and has a
   narrow bandwidth
B. It requires a large area for proper installation and has a
   low front-to-back ratio
C. It requires a large amount of aluminum tubing and has a low
   front-to-back ratio
D. It requires a large area and four sturdy supports for proper
   installation
*
414I-3B4 D 9-7  700 to 800 ohms
What is the characteristic impedance at the input of a
nonresonant rhombic antenna?
A. 50 to 55 ohms
B. 70 to 75 ohms
C. 300 to 350 ohms
D. 700 to 800 ohms
*
415I-3C1 B 9-6  Changes the radiation pattern
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
*
416I-3C2 C 9-7  Same as the Input Impedance|which is 700 to 800 ohms
What should be the value of the terminating resistor on a
rhombic antenna?
A. About 50 ohms
B. About 75 ohms
C. About 800 ohms
D. About 1800 ohms
*
417I-4A1 A 9-8  Transmitter power and antennas of satellite
What factors determine the receiving antenna gain required
at an amateur station in earth operation?
A. Height, transmitter power and antennas of satellite
B. Length of transmission line and impedance match between
   receiver and transmission line
C. Preamplifier location on transmission line and presence
   or absence of RF amplifier stages
D. Height of earth antenna and satellite orbit
*
418I-4A2 A 9-8  Satellite receiver sensitivity
What factors determine the EIRP required by an amateur station
in earth operation?
A. Satellite antennas and height, satellite receiver sensitivity
B. Path loss, earth antenna gain, signal-to-noise ratio
C. Satellite transmitter power and orientation of ground receiving
    antenna
D. Elevation of satellite above horizon, signal-to-noise ratio,
   satellite transmitter power
*
419I-4A3 B 9-8  Satellite receiver sensitivity
What factors determine the EIRP required by an amateur station
in telecommand operation?
A. Path loss, earth antenna gain, signal-to-noise ratio
B. Satellite antennas and height, satellite receiver sensitivity
C. Satellite transmitter power and orientation of ground receiving
    antenna
D. Elevation of satellite above horizon, signal-to-noise ratio,
   satellite transmitter power
*
420I-4A4 C 9-7  6 dB
How does the gain of a parabolic dish type antenna change
when the operating frequency is doubled?
A. Gain does not change
B. Gain is multiplied by 0.707
C. Gain increases 6 dB
D. Gain increases 3 dB
*
421I-4B1 D 9-8  Beamwidth decreases as gain increases
What happens to the beamwidth of an antenna as the gain is
increased?
A. The beamwidth increases geometrically as the gain is
   increased
B. The beamwidth increases arithmetically as the gain is
   increased
C. The beamwidth is essentially unaffected by the gain of
   the antenna
D. The beamwidth decreases as the gain is increased
*
422I-4B2 B 9-9  Remember 20/20    Otherwise GR = 10(dBi/10)|GR = 10(2), GR=100, Beamwidth = 203/SQR(GR)|Beamwidth = 203/10,  Beamwidth = 20.3°
What is the beamwidth of a symmetrical pattern antenna with
a gain of 20 dB as compared to an isotropic radiator?
A. 10.1 degrees
B. 20.3 degrees
C. 45.0 degrees
D. 60.9 degrees
*
423I-4B3 B 9-9  GR = 10(dBi/10), GR = 10(3), GR=1000|Beamwidth = 203/√(GR),  BmW = 203/31.6|Beamwidth = 6.42°
What is the beamwidth of a symmetrical pattern antenna with
a gain of 30 dB as compared to an isotropic radiator?
A. 3.2 degrees
B. 6.4 degrees
C. 37 degrees
D. 60.4 degrees
*
424I-4B4 C 9-9  GR = 10(dBi/10), GR = 10(15/10), GR = 31.6|Beamwidth = 203/√(GR),  Beamwidth = 203/5.62|Beamwidth = 36.1°
What is the beamwidth of a symmetrical pattern antenna with
a gain of 15 dB as compared to an isotropic radiator?
A. 72 degrees
B. 52 degrees
C. 36.1 degrees
D. 3.61 degrees
*
425I-4B5 D 9-9  GR = 10(dBi/10), GR = 10(12/10), GR = 15.9|Beamwidth = 203/√(GR),  Beamwidth = 203/3.98|Beamwidth = 51.0°
What is the beamwidth of a symmetrical pattern antenna with
a gain of 12 dB as compared to an isotropic radiator?
A. 34.8 degrees
B. 45.0 degrees
C. 58.0 degrees
D. 51.0 degrees
*
426I-4C1 C 9-10 Two Yagis perpendicular to each other|Driven elements in the same plane and|Fed 90 degrees out of phase
How is circular polarization produced using linearly-polarized
antennas?
A. Stack two Yagis, fed 90 degrees out of phase, to form an
   array with the respective elements in parallel planes
B. Stack two Yagis, fed in phase, to form an array with the
   respective elements in parallel planes
C. Arrange two Yagis perpendicular to each other, with the
   driven elements in the same plane, and fed 90 degrees out
   of phase
D. Arrange two Yagis perpendicular to each other, with the
   driven elements in the same plane, and fed in phase
*
427I-4C2 C 9-10 Amateur satellites are non-geosynchronous  |and must be tracked as they orbit the earth
Why does an antenna system for earth operation (for communications
through a satellite) need to have rotators for both azimuth and
elevation control?
A. In order to point the antenna above the horizon to avoid
   terrestrial interference
B. Satellite antennas require two rotators because they are so
   large and heavy
C. In order to track the satellite as it orbits the earth
D. The elevation rotator points the antenna at the satellite and
   the azimuth rotator changes the antenna polarization
*
428I-5.1 B 9-11 Delta matching
What term describes a method used to match a high-impedance
transmission line to a lower impedance antenna by connecting the
line to the driven element in two places, spaced a fraction of a
wavelength on each side of the driven element center?
A. The gamma matching system
B. The delta matching system
C. The omega matching system
D. The stub matching system
*
429I-5.2 A 9-11 Gamma matching
What term describes an unbalanced feed system in which the
driven element is fed both at the center of that element
and a fraction of a wavelength to one side of center?
A. The gamma matching system
B. The delta matching system
C. The omega matching system
D. The stub matching system
*
430I-5.3 D 9-12 Stub matching
What term describes a method of antenna impedance matching
that uses a short section of transmission line connected to
the antenna feed line near the antenna and perpendicular to
the feed line?
A. The gamma matching system
B. The delta matching system
C. The omega matching system
D. The stub matching system
*
431I-5.4 B 9-12 7 pF per meter|Cap. = 20*7 pF
What should be the approximate capacitance of the resonating
capacitor in a gamma matching circuit on a 1/2 wavelength
dipole antenna for the 20-meter wavelength band?
A. 70 pF
B. 140 pF
C. 200 pF
D. 0.2 pF
*
432I-5.5 A 9-12 7 pF per meter|Cap. = 10*7 pF
What should be the approximate capacitance of the resonating
capacitor in a gamma matching circuit on a 1/2 wavelength
dipole antenna for the 10-meter wavelength band?
A. 70 pF
B. 140 pF
C. 200 pF
D. 0.2 pF
*
433I-6A1 C 9-15 Inductive
What kind of impedance does a 1/8-wavelength transmission line
present to a generator when the line is shorted at the far end?
A. A capacitive reactance
B. The same as the characteristic impedance of the line
C. An inductive reactance
D. The same as the input impedance to the final generator stage
*
434I-6A2 C 9-14 Capacitive
What kind of impedance does a 1/8-wavelength transmission line
present to a generator when the line is open at the far end?
A. The same as the characteristic impedance of the line
B. An inductive reactance
C. A capacitive reactance
D. The same as the input impedance to the final generator stage
*
435I-6B1 A 9-15 Impedance maximums and minimums are 1/4|wavelength apart on the line so a short|would be a high impedance at the input
What kind of impedance does a 1/4-wavelength transmission line
present to a generator when the line is shorted at the far end?
A. A very high impedance
B. A very low impedance
C. The same as the characteristic impedance of the transmission
   line
D. The same as the generator output impedance
*
436I-6B2 B 9-14 Impedance maximums and minimums are|1/4-wavelength apart on the line
What kind of impedance does a 1/4-wavelength transmission line
present to a generator when the line is open at the far end?
A. A very high impedance
B. A very low impedance
C. The same as the characteristic impedance of the line
D. The same as the input impedance to the final generator stage
*
437I-6C1 C 9-15 The line would be inductive for the first|1/4-wavelength from the short and then be|a capacitive reactance for the next 1/4
What kind of impedance does a 3/8-wavelength transmission line
present to a generator when the line is shorted at the far end?
A. The same as the characteristic impedance of the line
B. An inductive reactance
C. A capacitive reactance
D. The same as the input impedance to the final generator stage
*
438I-6C2 C 9-14 The line would be capacitive for the first |1/4-wavelength from the open and then be an|inductive reactance for the next 1/4
What kind of impedance does a 3/8-wavelength transmission line
present to a generator when the line is open at the far end?
A. A capacitive reactance
B. The same as the characteristic impedance of the line
C. An inductive reactance
D. The same as the input impedance to the final generator stage
*
439I-6D1 B 9-15 Impedance minimums are 1/2-wavelength|apart on the line so a short would be|a very low impedance at the generator
What kind of impedance does a 1/2-wavelength transmission line
present to a generator when the line is shorted at the far end?
A. A very high impedance
B. A very low impedance
C. The same as the characteristic impedance of the line
D. The same as the output impedance of the generator
*
440I-6D2 A 9-14 Impedance maximums are 1/2-wavelength |apart on the line so an open would be |a very high impedance at the generator
What kind of impedance does a 1/2-wavelength transmission line
present to a generator when the line is open at the far end?
A. A very high impedance
B. A very low impedance
C. The same as the characteristic impedance of the line
D. The same as the output impedance of the generator
*