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1993-03-09
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305 lines
256I-3.7 B 9-8 Lde = 468/Fmhz, Lde = 468/14.0|Lde = 33.4, ie. Lde ≈ 33 feet
How long is the driven element of a Yagi antenna for
14.0-MHz?
A. Approximately 17 feet
B. Approximately 33 feet
C. Approximately 35 feet
D. Approximately 66 feet
*
257I-3.8 B 9-8 Lde = 468/Fmhz, Lde = 468/21.1|Lde = 22.18, Ldr = .95*Lde|Ldr = .95*22.18, Ldr = 21.07
How long is the director element of a Yagi antenna for
21.1-MHz?
A. Approximately 42 feet
B. Approximately 21 feet
C. Approximately 17 feet
D. Approximately 10.5 feet
*
258I-3.9 C 9-8 Lde = 468/Fmhz, Lde = 468/28.1|Lde = 16.65, Lr = 1.05*Lde|Lr = 1.05*16.65, Lr = 17.48
How long is the reflector element of a Yagi antenna for
28.1-MHz?
A. Approximately 8.75 feet
B. Approximately 16.6 feet
C. Approximately 17.5 feet
D. Approximately 35 feet
*
259I-5.1 D 9-3 ≈ 73 Ω real, ie. resistive
What is the feed-point impedance for a half-wavelength dipole HF
antenna suspended horizontally one-quarter wavelength or more
above the ground?
A. Approximately 50 ohms, resistive
B. Approximately 73 ohms, resistive and inductive
C. Approximately 50 ohms, resistive and capacitive
D. Approximately 73 ohms, resistive
*
260I-5.2 B 9-11 ≈ 36 Ω
What is the feed-point impedance of a quarter-wavelength vertical
HF antenna with a horizontal ground plane?
A. Approximately 18 ohms
B. Approximately 36 ohms
C. Approximately 52 ohms
D. Approximately 72 ohms
*
261I-5.3 D 9-13 Raises feed-point impedance to ≈ 50 Ω
What is an advantage of downward sloping radials on a ground-
plane antenna?
A. Sloping the radials downward lowers the radiation angle
B. Sloping the radials downward brings the feed-point impedance
close to 300 ohms
C. Sloping the radials downward allows rainwater to run off the
antenna
D. Sloping the radials downward brings the feed-point impedance
closer to 50 ohms
*
262I-5.4 B 9-13 Raises impedance compared|to being straight out
What happens to the feed-point impedance of a ground-plane
antenna when the radials slope downward from the base of the
antenna?
A. The feed-point impedance decreases
B. The feed-point impedance increases
C. The feed-point impedance stays the same
D. The feed-point impedance becomes purely capacitive
*
263I-6.1 C 9-11 More directivity in both the planes|The greater the directivity of the |antenna, the greater the gain
Compared to a dipole antenna, what are the directional radiation
characteristics of a cubical quad HF antenna?
A. The quad has more directivity in the horizontal plane but less
directivity in the vertical plane
B. The quad has less directivity in the horizontal plane but more
directivity in the vertical plane
C. The quad has more directivity in both horizontal and vertical
planes
D. The quad has less directivity in both horizontal and vertical
planes
*
264I-6.2 A 9-3 If installed parallel to the earth, |maximun radiation is at 90° to the |antenna wire, ie. a figure-8 pattern
What is the radiation pattern of an ideal half-wavelength dipole
HF antenna?
A. If it is installed parallel to the earth, it radiates well in
a figure-eight pattern at right angles to the antenna wire
B. If it is installed parallel to the earth, it radiates well in
a figure-eight pattern off both ends of the antenna wire
C. If it is installed parallel to the earth, it radiates equally
well in all directions
D. If it is installed parallel to the earth, the pattern will have
two lobes on one side of the antenna wire, and one larger lobe
on the other side
*
265I-6.3 B 9-3 If the antenna is too close to ground|the pattern is distorted
How does proximity to the ground affect the radiation pattern
of a horizontal dipole HF antenna?
A. If the antenna is too far from the ground, the pattern
becomes unpredictable
B. If the antenna is less than one-half wavelength from the
ground, reflected radio waves from the ground distort the
radiation pattern of the antenna
C. A dipole antenna's radiation pattern is unaffected by its
distance to the ground
D. If the antenna is less than one-half wavelength from the
ground, radiation off the ends of the wire is reduced
*
266I-6.4 C 9-10 Power radiated forward compared to |the power radiated to the rear, ie.|in exactly the opposite direction
What does the term antenna front-to-back ratio mean?
A. The number of directors versus the number of reflectors
B. The relative position of the driven element with respect
to the reflectors and directors
C. The power radiated in the major radiation lobe compared
to the power radiated in exactly the opposite direction
D. The power radiated in the major radiation lobe compared
to the power radiated 90 degrees away from that direction
*
267I-6.5 D 9-5 Radiated power will increase in the|direction of the added element and |decrease in the opposite direction
What effect upon the radiation pattern of an HF dipole antenna
will a slightly smaller parasitic parallel element located a few
feet away in the same horizontal plane have?
A. The radiation pattern will not change appreciably
B. A major lobe will develop in the horizontal plane, parallel
to the two elements
C. A major lobe will develop in the vertical plane, away from
the ground
D. If the spacing is greater than 0.1 wavelength, a major lobe
will develop in the horizontal plane to the side of the driven
element toward the parasitic element
*
268I-6.6 C 9-5 The direction that has the greatest|amount of radiated power
What is the meaning of the term main lobe as used in reference to
a directional antenna?
A. The direction of least radiation from an antenna
B. The point of maximum current in a radiating antenna element
C. The direction of maximum radiated field strength from a
radiating antenna
D. The maximum voltage standing wave point on a radiating element
*
269I-7.1 A 9-13 Radius of the conductors |and spacing between them
Upon what does the characteristic impedance of a parallel-conductor
antenna feed line depend?
A. The distance between the centers of the conductors and the
radius of the conductors
B. The distance between the centers of the conductors and the
length of the line
C. The radius of the conductors and the frequency of the signal
D. The frequency of the signal and the length of the line
*
270I-7.2 B 9-15 The two most common impedances used |for coax feedlines are 50 Ω and 75 Ω|75 Ω is also used for TV and video
What is the characteristic impedance of various coaxial cables
commonly used for antenna feed lines at amateur stations?
A. Around 25 and 30 ohms
B. Around 50 and 75 ohms
C. Around 80 and 100 ohms
D. Around 500 and 750 ohms
*
271I-7.3 A 9-16 None
What effect, if any, does the length of a coaxial cable have
upon its characteristic impedance?
A. The length has no effect on the characteristic impedance
B. The length affects the characteristic impedance primarily
above 144 MHz
C. The length affects the characteristic impedance primarily
below 144 MHz
D. The length affects the characteristic impedance at any
frequency
*
272I-7.4 D 9-14 300 Ω
What is the characteristic impedance of flat-ribbon TV-type
twinlead?
A. 50 ohms
B. 75 ohms
C. 100 ohms
D. 300 ohms
*
273I-8.4 C 9-17 A mismatch between the antenna and|feedline, ie. a difference between|the line and feed-point impedances
What is the cause of power being reflected back down an antenna
feed line?
A. Operating an antenna at its resonant frequency
B. Using more transmitter power than the antenna can handle
C. A difference between feed line impedance and antenna feed-
point impedance
D. Feeding the antenna with unbalanced feed line
*
274I-9.3 A 9-17 SWR = R/Zo, SWR = 200/50, SWR = 4:1|Second digit always 1
What will be the standing wave ratio when a 50 ohm feed line
is connected to a resonant antenna having a 200 ohm feed-point
impedance?
A. 4:1
B. 1:4
C. 2:1
D. 1:2
*
275I-9.4 D 9-17 SWR = Zo/R, SWR = 50/10, SWR = 5:1|Second digit always 1
What will be the standing wave ratio when a 50 ohm feed line
is connected to a resonant antenna having a 10 ohm feed-point
impedance?
A. 2:1
B. 50:1
C. 1:5
D. 5:1
*
276I-9.5 C 9-17 SWR = R/Zo, SWR = 50/50, SWR = 1:1|Second digit always 1
What will be the standing wave ratio when a 50 ohm feed line
is connected to a resonant antenna having a 50 ohm feed-point
impedance?
A. 2:1
B. 50:50
C. 1:1
D. 0:0
*
277I-11.1 C 9-16 Attenuation is independent|of Zo below 1.5 GHz
How does the characteristic impedance of a coaxial cable affect
the amount of attenuation to the RF signal passing through it?
A. The attenuation is affected more by the characteristic
impedance at frequencies above 144 MHz than at frequencies
below 144 MHz
B. The attenuation is affected less by the characteristic
impedance at frequencies above 144 MHz than at frequencies
below 144 MHz
C. The attenuation related to the characteristic impedance is
about the same at all amateur frequencies below 1.5 GHz
D. The difference in attenuation depends on the emission type
in use
*
278I-11.2 A 9-16 The higher the frequency|the greater the losses
How does the amount of attenuation to a 2 meter signal passing
through a coaxial cable differ from that to a 160 meter signal?
A. The attenuation is greater at 2 meters
B. The attenuation is less at 2 meters
C. The attenuation is the same at both frequencies
D. The difference in attenuation depends on the emission type
in use
*
279I-11.4 D 9-14 Attenuation increases|when the lead is wet
What is the effect on its attenuation when flat-ribbon TV-type
twinlead is wet?
A. Attenuation decreases slightly
B. Attenuation remains the same
C. Attenuation decreases sharply
D. Attenuation increases
*
280I-11.7 B 9-15 To keep it dry
Why might silicone grease or automotive car wax be applied to
flat-ribbon TV-type twinlead?
A. To reduce "skin effect" losses on the conductors
B. To reduce the buildup of dirt and moisture on the feed line
C. To increase the velocity factor of the feed line
D. To help dissipate heat during high-SWR operation
*
281I-11.8 D 9-14 dB per hundred feet
In what values are RF feed line losses usually expressed?
A. Bels/1000 ft
B. dB/1000 ft
C. Bels/100 ft
D. dB/100 ft
*
282I-11.10 D 9-14 The higher the frequency|the greater the losses
As the operating frequency increases, what happens to the
dielectric losses in a feed line?
A. The losses decrease
B. The losses decrease to zero
C. The losses remain the same
D. The losses increase
*
283I-11.12 A 9-14 As the operating frequency is|decreased the losses decrease
As the operating frequency decreases, what happens to the
dielectric losses in a feed line?
A. The losses decrease
B. The losses increase
C. The losses remain the same
D. The losses become infinite
*
284I-12.1 D 9-17 The impedances of the transmission |line and the antenna feed-point must|be matched
What condition must be satisfied to prevent standing waves of
voltage and current on an antenna feed line?
A. The antenna feed point must be at DC ground potential
B. The feed line must be an odd number of electrical quarter
wavelengths long
C. The feed line must be an even number of physical half
wavelengths long
D. The antenna feed-point impedance must be matched to the
characteristic impedance of the feed line
*
285I-12.2 A 9-18 The answer to this question is A, but|inductive coupling is used in resonant|antenna systems other than dipoles
How is an inductively-coupled matching network used in an antenna
system consisting of a center-fed resonant dipole and coaxial feed
line?
A. An inductively coupled matching network is not normally used in
a resonant antenna system
B. An inductively coupled matching network is used to increase the
SWR to an acceptable level
C. An inductively coupled matching network can be used to match the
unbalanced condition at the transmitter output to the balanced
condition required by the coaxial line
D. An inductively coupled matching network can be used at the
antenna feed point to tune out the radiation resistance
*
286I-12.5 D 9-17 A mismatch occurs when the impedance|of the feed line does not match the |feed-point impedance of the antenna
What is an antenna-transmission line mismatch?
A. A condition where the feed-point impedance of the antenna
does not equal the output impedance of the transmitter
B. A condition where the output impedance of the transmitter
does not equal the characteristic impedance of the feed line
C. A condition where a half-wavelength antenna is being fed with
a transmission line of some length other than one-quarter
wavelength at the operating frequency
D. A condition where the characteristic impedance of the feed
line does not equal the feed-point impedance of the antenna
*