HAM Radio 3/hamradioversion3.0examsandprograms1992.iso/exam/adv20/adv9.dat

Text File | 1991-11-20 | 17KB | 459 lines

456H-10.1  D 8-11  Atmospheric noise
Where is the noise generated which primarily determines the signal-
to-noise ratio in a 160-meter wavelength band receiver?
A. In the detector
B. Man-made noise
C. In the receiver front end
D. In the atmosphere
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457H-10.2  A 8-12  Receiver or preamp noise
Where is the noise generated which primarily determines the signal-
to-noise ratio in a 2-meter wavelength band receiver?
A. In the receiver front end
B. Man-made noise
C. In the atmosphere
D. In the ionosphere
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458H-10.3  B 8-12  Receiver or preamp noise
Where is the noise generated which primarily determines the signal-
to-noise ratio in a 1.25-meter wavelength band receiver?
A. In the audio amplifier
B. In the receiver front end
C. In the ionosphere
D. Man-made noise
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459H-10.4  C 8-12  Receiver or preamp noise
Where is the noise generated which primarily determines the signal-
to-noise ratio in a 0.70-meter wavelength band receiver?
A. In the atmosphere
B. In the ionosphere
C. In the receiver front end
D. Man-made noise
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460I-1.1   A 9-11  Ratio of radiated signal|strength to a reference
What is meant by the term antenna gain?
A. The numerical ratio relating the radiated signal
   strength of an antenna to that of another antenna
B. The ratio of the signal in the forward direction to
   the signal in the back direction
C. The ratio of the amount of power produced by the
   antenna compared to the output power of the transmitter
D. The final amplifier gain minus the transmission line
   losses (including any phasing lines present)
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461I-1.2   B 9-11  Gain
What is the term for a numerical ratio which relates the performance
of one antenna to that of another real or theoretical antenna?
A. Effective radiated power
B. Antenna gain
C. Conversion gain
D. Peak effective power
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462I-1.3   B 9-11  The frequency range over which|an antenna performs well
What is meant by the term antenna bandwidth?
A. Antenna length divided by the number of elements
B. The frequency range over which an antenna can be
   expected to perform well
C. The angle between the half-power radiation points
D. The angle formed between two imaginary lines drawn
   through the ends of the elements
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463I-1.4   A 9-11  Rotate antenna and record|half power (3 dB) points
How can the approximate beamwidth of a rotatable beam antenna
be determined?
A. Note the two points where the signal strength of the antenna
   is down 3 dB from the maximum signal point and compute the
   angular difference
B. Measure the ratio of the signal strengths of the radiated
   power lobes from the front and rear of the antenna
C. Draw two imaginary lines through the ends of the elements
   and measure the angle between the lines
D. Measure the ratio of the signal strengths of the radiated
   power lobes from the front and side of the antenna
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464I-2.1   C 9-5   Multiband antenna
What is a trap antenna?
A. An antenna for rejecting interfering signals
B. A highly sensitive antenna with maximum gain in all
   directions
C. An antenna capable of being used on more than one band
   because of the presence of parallel LC networks
D. An antenna with a large capture area
*
465I-2.2   D 9-6   Multiband antenna
What is an advantage of using a trap antenna?
A. It has high directivity in the high-frequency
   amateur bands
B. It has high gain
C. It minimizes harmonic radiation
D. It may be used for multiband operation
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466I-2.3   A 9-7   Multiband antenna will|radiate harmonics
What is a disadvantage of using a trap antenna?
A. It will radiate harmonics
B. It can only be used for single band operation
C. It is too sharply directional at the lower
   amateur frequencies
D. It must be neutralized
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467I-2.4   B 9-5   The traps isolate parts of the|antenna for a given band
What is the principle of a trap antenna?
A. Beamwidth may be controlled by non-linear impedances
B. The traps form a high impedance to isolate parts of
   the antenna
C. The effective radiated power can be increased if the
   space around the antenna "sees" a high impedance
D. The traps increase the antenna gain
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468I-3.1   C 9-10  Non-driven element
What is a parasitic element of an antenna?
A. An element polarized 90 degrees opposite the driven element
B. An element dependent on the antenna structure for support
C. An element that receives its excitation from mutual coupling
   rather than from a transmission line
D. A transmission line that radiates radio-frequency energy
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469I-3.2   D 9-10  By induced currents
How does a parasitic element generate an electromagnetic field?
A. By the RF current received from a connected transmission line
B. By interacting with the earth's magnetic field
C. By altering the phase of the current on the driven element
D. By currents induced into the element from a surrounding
   electric field
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470I-3.3   A 9-10  Lr ≈ 1.05*Lde
How does the length of the reflector element of a parasitic
element beam antenna compare with that of the driven element?
A. It is about 5% longer
B. It is about 5% shorter
C. It is twice as long
D. It is one-half as long
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471I-3.4   B 9-10  Ld ≈ .95*Lde
How does the length of the director element of a parasitic
element beam antenna compare with that of the driven element?
A. It is about 5% longer
B. It is about 5% shorter
C. It is one-half as long
D. It is twice as long
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472I-4.1   C 9-8   Equivalent resistance
What is meant by the term radiation resistance for an
antenna?
A. Losses in the antenna elements and feed line
B. The specific impedance of the antenna
C. An equivalent resistance that would dissipate the
   same amount of power as that radiated from an antenna
D. The resistance in the trap coils to received signals
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473I-4.2   D 9-8   Radiation resistance
What is the term used for an equivalent resistance which would
dissipate the same amount of energy as that radiated from an
antenna?
A. Space resistance
B. Loss resistance
C. Transmission line loss
D. Radiation resistance
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474I-4.3   A 9-9   Helps in the matching process
Why is the value of the radiation resistance of an antenna
important?
A. Knowing the radiation resistance makes it possible to match
   impedances for maximum power transfer
B. Knowing the radiation resistance makes it possible to measure
   the near-field radiation density from a transmitting antenna
C. The value of the radiation resistance represents the front-
   to-side ratio of the antenna
D. The value of the radiation resistance represents the front-
   to-back ratio of the antenna
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475I-4.4   B 9-9   Distance to objects and|antenna physical shape
What are the factors that determine the radiation resistance
of an antenna?
A. Transmission line length and height of antenna
B. The location of the antenna with respect to nearby objects
   and the length/diameter ratio of the conductors
C. It is a constant for all antennas since it is a physical
   constant
D. Sunspot activity and the time of day
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476I-5.1   C 9-4   The element connected|to transmission line
What is a driven element of an antenna?
A. Always the rearmost element
B. Always the forwardmost element
C. The element fed by the transmission line
D. The element connected to the rotator
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477I-5.2   B 9-4   .5 wavelength
What is the usual electrical length of a driven element
in an HF beam antenna?
A. 1/4 wavelength
B. 1/2 wavelength
C. 3/4 wavelength
D. 1 wavelength
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478I-5.3   A 9-4   Driven element
What is the term for an antenna element which is supplied
power from a transmitter through a transmission line?
A. Driven element
B. Director element
C. Reflector element
D. Parasitic element
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479I-6.1   B 9-9   Ωr/Ωt
What is meant by the term antenna efficiency?
                   radiation resistance
A.  Efficiency =  ───────────────────────  X 100%
                  transmission resistance
                  radiation resistance
B.  Efficiency =  ────────────────────  X 100%
                    total resistance
                    total resistance
C.  Efficiency =  ────────────────────  X 100%
                  radiation resistance
                  effective radiated power
D.  Efficiency =  ────────────────────────  X 100%
                     transmitter output
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480I-6.2   C 9-9   Efficiency
What is the term for the ratio of the radiation resistance
of an antenna to the total resistance of the system?
A. Effective radiated power
B. Radiation conversion loss
C. Antenna efficiency
D. Beamwidth
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481I-6.3   D 9-9   Radiation resistance and losses
What is included in the total resistance of an antenna system?
A. Radiation resistance plus space impedance
B. Radiation resistance plus transmission resistance
C. Transmission line resistance plus radiation resistance
D. Radiation resistance plus ohmic resistance
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482I-6.4   A 9-9   Good ground
How can the antenna efficiency of an HF grounded vertical
antenna be made comparable to that of a half-wave antenna?
A. By installing a good ground radial system
B. By isolating the coax shield from ground
C. By shortening the vertical
D. By lengthening the vertical
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483I-6.5   B 9-9   High radiation resistance
Why does a half-wave antenna operate at very high efficiency?
A. Because it is non-resonant
B. Because the conductor resistance is low compared to the
   radiation resistance
C. Because earth-induced currents add to its radiated power
D. Because it has less corona from the element ends than other
   types of antennas
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484I-7.1   C 9-7   Parallel wire(or tubing) dipole
What is a folded dipole antenna?
A. A dipole that is one-quarter wavelength long
B. A ground plane antenna
C. A dipole whose ends are connected by another one-half
   wavelength piece of wire
D. A fictional antenna used in theoretical discussions
   to replace the radiation resistance
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485I-7.2   D 9-8   Greater
How does the bandwidth of a folded dipole antenna
compare with that of a simple dipole antenna?
A. It is 0.707 times the simple dipole bandwidth
B. It is essentially the same
C. It is less than 50% that of a simple dipole
D. It is greater
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486I-7.3   A 9-8   ≈ 300 Ω
What is the input terminal impedance at the center
of a folded dipole antenna?
A. 300 ohms
B. 72 ohms
C. 50 ohms
D. 450 ohms
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487I-8.1   D 9-2   Radio waves travel slower in cables|in than space.  The velocity factor|is always one or less than one
What is the meaning of the term velocity factor of a transmission
line?
A. The ratio of the characteristic impedance of the line to the
   terminating impedance
B. The index of shielding for coaxial cable
C. The velocity of the wave on the transmission line multiplied
   by the velocity of light in a vacuum
D. The velocity of the wave on the transmission line divided by
   the velocity of light in a vacuum
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488I-8.2   A 9-2   Velocity factor is about 2/3 for coax
What is the term for the ratio of actual velocity at which a signal
travels through a line to the speed of light in a vacuum?
A. Velocity factor
B. Characteristic impedance
C. Surge impedance
D. Standing wave ratio
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489I-8.3   B 9-2   Velocity factor is about 2/3 for coax
What is the velocity factor for a typical coaxial
cable?
A. 2.70
B. 0.66
C. 0.30
D. 0.10
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490I-8.4   C 9-2   Dielectics
What determines the velocity factor in a transmission
line?
A. The termination impedance
B. The line length
C. Dielectrics in the line
D. The center conductor resistivity
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491I-8.5   B 9-2   Radio waves travel slower|in cables than space
Why is the physical length of a coaxial cable transmission
line shorter than its electrical length?
A. Skin effect is less pronounced in the coaxial cable
B. RF energy moves slower along the coaxial cable
C. The surge impedance is higher in the parallel feed line
D. The characteristic impedance is higher in the parallel
   feed line
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492I-9.1   B 9-2   Velocity factor is about 2/3 for coax|Wavelength = 300/14.1 = 21.28 Meters |.25*21.28 = 5.32,  2/3 of 5.32 = 3.51
What would be the physical length of a typical coaxial transmission
line which is electrically one-quarter wavelength long at 14.1 MHz?
A. 20 meters
B. 3.51 meters
C. 2.33 meters
D. 0.25 meters
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493I-9.2   B 9-2   300/7.2 = 41.7 Mtrs,  ¼*41.7 = 10.4|10.4*.66 = 6.8
What would be the physical length of a typical coaxial transmission
line which is electrically one-quarter wavelength long at 7.2 MHz?
A. 10.5 meters
B. 6.88 meters
C. 24 meters
D. 50 meters
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494I-9.3   C 9-2   14 Mhz ≈ 21 Mtrs,  ½*21=10.5|.82*10.5 = 8.6
What is the physical length of a parallel antenna feedline which
is electrically one-half wavelength long at 14.10 MHz? (assume a
velocity factor of 0.82.)
A. 15 meters
B. 24.3 meters
C. 8.7 meters
D. 70.8 meters
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495I-9.4   A 9-2   Wavelength times .8
What is the physical length of a twin lead transmission
feedline at 3.65 MHz? (assume a velocity factor of 0.80.)
A. Electrical length times 0.8
B. Electrical length divided by 0.8
C. 80 meters
D. 160 meters
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496I-10.1  A 9-5   Current node is current minimum
In a half-wave antenna, where are the current nodes?
A. At the ends
B. At the center
C. Three-quarters of the way from the feed point toward
   the end
D. One-half of the way from the feed point toward the
   end
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497I-10.2  B 9-5   Voltage node is voltage minimum
In a half-wave antenna, where are the voltage nodes?
A. At the ends
B. At the feed point
C. Three-quarters of the way from the feed point toward
   the end
D. One-half of the way from the feed point toward the
   end
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498I-10.3  C 9-5   Voltage is maximum
At the ends of a half-wave antenna, what values of current
and voltage exist compared to the remainder of the antenna?
A. Equal voltage and current
B. Minimum voltage and maximum current
C. Maximum voltage and minimum current
D. Minimum voltage and minimum current
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499I-10.4  D 9-5   Voltage is minimum
At the center of a half-wave antenna, what values of voltage
and current exist compared to the remainder of the antenna?
A. Equal voltage and current
B. Maximum voltage and minimum current
C. Minimum voltage and minimum current
D. Minimum voltage and maximum current
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500I-11.1  A 9-12  More capacitance at base
Why is the inductance required for a base loaded HF mobile
antenna less than that for an inductance placed further up
the whip?
A. The capacitance to ground is less farther away from the
   base
B. The capacitance to ground is greater farther away from
   the base
C. The current is greater at the top
D. The voltage is less at the top
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501I-11.2  B 9-12  Resistance decreases and capacitive|reactance increases
What happens to the base feed point of a fixed length HF
mobile antenna as the frequency of operation is lowered?
A. The resistance decreases and the capacitive reactance
   decreases
B. The resistance decreases and the capacitive reactance
   increases
C  The resistance increases and the capacitive reactance
   decreases
D  The resistance increases and the capacitive reactance
   increases
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502I-11.3  C 9-12  Minimize losses
Why should an HF mobile antenna loading coil have a high
ratio of reactance to resistance?
A. To swamp out harmonics
B. To maximize losses
C. To minimize losses
D. To minimize the Q
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503I-11.4  D 9-12  Tune out the capacitive reactance
Why is a loading coil often used with an HF mobile
antenna?
A. To improve reception
B. To lower the losses
C. To lower the Q
D. To tune out the capacitive reactance
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504I-12.1  A 9-12  Middle
For a shortened vertical antenna, where should a loading
coil be placed to minimize losses and produce the most
effective performance?
A. Near the center of the vertical radiator
B. As low as possible on the vertical radiator
C. As close to the transmitter as possible
D. At a voltage node
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505I-12.2  B 9-13  Narrows
What happens to the bandwidth of an antenna as it is
shortened through the use of loading coils?
A. It is increased
B. It is decreased
C. No change occurs
D. It becomes flat
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506I-12.3  C 9-14  Efficient
Why are self-resonant antennas popular in amateur
stations?
A. They are very broad banded
B. They have high gain in all azimuthal directions
C. They are the most efficient radiators
D. They require no calculations
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507I-12.4  D 9-12  Efficient
What is an advantage of using top loading in a shortened
HF vertical antenna?
A. Lower Q
B. Greater structural strength
C. Higher losses
D. Improved radiation efficiency
*