RHM 1 ESAT PART 1
RF and Communication Quiz
Test your knowledge on radio frequency and communication technologies with this comprehensive quiz featuring 102 questions designed for enthusiasts and professionals alike!
- Covering a wide range of topics including SWR, modulation, and antenna systems.
- Gain insights into the essential concepts that shape the world of radio communication.
A 50 Ω Line is terminated in a 25 Ω resistance. Find the SWR.
A. 0.5
B. 2
C. 0.3333
D. 3
Frequencies that encompass the 300- to 3000-MHz range are under which of the following segments
A. High frequency
B. Very high frequency
C. Ultrahigh frequency
D. microwave
Indicate the true statement. Most receivers conforms to the
A. amplitude-modulated group
B. frequency-modulated group
C. Superheterodyne group
D. Tuned radio frequency receiver group
Determine the amount of delay introduced by a 1-ft section of RG-8A/U coaxial cable used as a delay line.
A. 2.95 ns
B. 1.475 ns
C. 2.2125 ns
D. None if the above
In a frequency modulation transmitter, the _______ is located between the modulator and the frequency multiplier.
A. Speech amplifier
B. oscillator
C. Power amplifier
D. microphone
In a frequency modulation transmitter, the _______ is located between the oscillator and the power amplifier.
A. Frequency multiplier
B. microphone
C. Speech amplifier
D. modulator
Which of the steps is not included in the process of reception?
A. decoding
B. encoding
C. storage
D. interpretation
Wireless local-area networks occupy which of the following segments?
A. High frequency
B. Very high frequency
C. UHF
D. Microwave and SHF
A citizen’s band transmitter operating at 27 MHz with 4W output is connected with RG-8A/U cable to an antenna that has an input resistance of 300Ω. Determine the VSWR.
A. 5
B. 6
C. 7
D. 8
A low pass filter in an HF station is most effective when connected:
A. As close as possible to the transceiver output
B. As close as possible to the antenna tuner output
C. As close as possible to the antenna midway between the transceiver and antenna
D. missing
Just above the infrared region is the spectrum referred to as
A. light
B. Millimeter waves
C. ultraviolet
C. ultraviolet
A low pass filter in an HF station is most effective when connected:
A. As close as possible to the antenna
B. As close as possible to the antenna tuner output
C. As close as possible to the linear amplifier input
D. As close as possible to the linear amplifier output
A transmitter supplies 50W to a load through a line with an SWR of 2:1. Find the power absorbed by the load.
A. 37.5 W
B. 44.4 W
C. 12.5 W
D. 5.56 W
The difference between the upper and lower frequency limits of a signal or the equipment operation range is the
A. amplitude
B. spectrum
C. bandwidth
D. medium
Many circles are drawn in a Smith chart used for transmission line calculations. The circle shown in the figure represents
A. Unit circles
B. Constant resistance circles
C. Constant reactance circles
D. Constant reflection coefficient circles
How should you position the antenna of a hand-held transceiver while you are transmitting?
A. Pointed towards the station you are contacting
B. Pointed away from the station you are contacting
C. Pointed down to bounce the signal off the ground
D. Away from your head and away from others
Indicate the false statement. The square of the thermal noise voltage generated by a resistor is proportional to
A. Its resistance
B. Its temperature
C. Boltzmann’s constant
D. The bandwidth over which it is measured
Two adjacent minima on a slotted line are 23 cm apart. Find the wavelength and the frequency, assuming a velocity factor of 95%.
A. 120 MHz
B. 676 MHz
C. 620 MHz
D. 176 MHz
What is meant by receiver overload?
A. Interference caused by turning the volume up too high
B. Too much current from the power supply
C. Interference caused by strong signals from a nearby transmitter
D. Too much voltage from the power supply
Amplitude modulation is the process of
A. Superimposing a low frequency on a high frequency
B. Superimposing a high frequency on a low frequency
C. Carrier interruption
D. Frequency shift and phase shift
In designing an HF station, which component would you use to reduce the effects of harmonic radiation?
A. Dummy load
B. Low pass filter
C. Antenna switch
D. SWR bridge
A series tuned circuit operating at a frequency of 1 GHz is to be constructed from a shorted section of air-dielectric coaxial cable. What length should be used?
A. 0.143m
B. Infinity
C. 0.356m
D. None of the above
The acoustic channel is used for which of the following?
A. UHF communications
B. single-sideband communication
C. Television communications
D. person-to-person voice communications
Signals generated at frequencies above and below a carrier frequency by an amount equal to the modulating frequency are called
A. Duplex signals
B. sidebands
C. Analog signals
D. Gamma rays
The forward power in a transmission line is 150 W, and the reverse power is 20 W. Calculate the SWR on the line.
A. 2.15
B. 2.74
C. 0.365
D. 0.465
Why should you make sure the antenna of a hand-held transceiver is not close to your head when transmitting?
A. To use your body to reflect the signal in one direction
B. To reduce your exposure to the radiofrequency energy
C. To keep static charges from building up
D. To help the antenna radiate energy equally in all directions
Which component in an HF station is the most useful for determining the effectiveness of the antenna system?
A. SWR bridge
B. Antenna switch
C. Linear amplifier
D. Dummy load
What agency is responsible for allocating bands of frequencies and for setting limitations on broadcast power for different types of radio and TV operations?
A. OSHA
B. IEEE
C. FCC
D. ANSI
Of the components in an HF station, which component would normally be connected closest to the antenna, antenna tuner and dummy load?
A. Transceiver
B. Low pass filter
C. Antenna switch
D. SWR bridge
A generator sends 50mW down a 50Ω line. The generator is matched to the line, but the load is not. If the coefficient of reflection is 0.5, how much power is reflected and how much is dissipated in the load?
A. 37.5 mW; 12.5 mW
B. 35 mW; 15 mW
C. 12.5 mW; 37.5 mW
D. 15 mW; 35 mW
Indicate the false statement. The need for modulation can best be exemplified by the following.
A. Antenna lengths will be approximately λ/4 long
B. An antenna in the standard broadcast AM band is 16,000 ft
C. All sound is concentrated from 20 Hz to 20 kHz
D. A message is composed of unpredictable variations in both amplitude and frequency
In a frequency modulation transmitter, the input to the speech amplifier is connected to the:
A. microphone
B. modulator
C. Power amplifier
D. Frequency multiplier
Determine the characteristics impedance for an RG-59A coaxial cable with the following specifications: L=0.118μH❄ft and C=21pF❄ft.
A. 50 ohms
B. 300 ohms
C. 75 ohms
D. None of the above
Which of the following organizations does not maintain standards for communication systems?
A. IEEE
B. ANSI
C. IBEW
D. ITU
Which of broad classifications of noise are most difficult to treat?
A. Noise generated in the receiver
B. Noise generated in the transmitter
C. Externally generated noise
D. Internally generated noise
What should you do for safety, before removing the shielding on a UHF power amplifier?
A. Make sure that RF leakage filters are connected
B. Make sure the antenna feed line is properly grounded
C. Make sure the amplifier cannot accidentally be turned on
D. Make sure all RF screens are in place at the antenna feed line
Space noise generally covers a wide frequency spectrum, but the strongest interference occurs
A. between 8 MHz and 1.43 GHz
B. below 20 MHz
C. between 20 to 120 MHz
D. above 1.5 GHz
Which of the following is not a simplex communication system?
A. TV broadcasting
B. Paging services
C. radar
D. facsimile
In a frequency modulation transmitter, the microphone is connected to the:
A. modulator
B. Power amplifier
C. Speech amplifier
D. oscillator
The value of a resistor creating thermal noise is doubled. The noise power generator is therefore
A. halved
B. quadrupled
C. doubled
D. unchanged
Which communication application best describes movies, sports events, and other programs that are distributed to subscribers by fiber-optic and coaxial cable?
A. telemetry
B. Cable television
C. TV broadcasting
D. wide-area networks
In a frequency modulation transmitter, the _______ is in between the speech amplifier and the oscillator.
A. modulator
B. Power amplifier
C. microphone
D. Frequency multiplier
Determine the characteristics impedance for an RG-59A coaxial cable with the following specification: d=0.025 inches, D=0.15 inches, and εr=2.23.
A. 71.9 ohms
B. 48.2 ohms
C. 32.2 ohms
D. None of the above
Indicate the true statement. The process of sending and receiving started as early as
A. The middle 1930s
B. 1850
C. The beginning of the twentieth century
D. the 1840s
Which of the following is not a duplex type communication system?
A. telephones
B. sonar
C. telemetry
D. Internet
What does a very high SWR reading mean?
A. The transmitter is putting out more power than normal, showing that it is about to go bad
B. The antenna is the wrong length, or there may be an open or shorted connection somewhere in the feed line
C. There is a large amount of solar radiation, which means very poor radio conditions
D. The signals coming from the antenna are unusually strong, which means very good radio conditions
One of the following is not a useful quantity for comparing the noise performance of receivers:
A. Input noise voltage
B. Equivalent noise resistance
C. Noise temperature
D. Noise figure
A pulse is transmitted down a cable that has a velocity of propagation of 0.8 c. The reflected signal is received 1 μs later. How far down the cable is the impairment?
A. 60 m
B. 120 m
C. 240 m
D. 80 m
A device’s interelement capacitance can be compensated for by feeding a 180° out of phase signal back through a capacitor in a process called
A. digitization
B. Internal compensation
C. neutralization
D. phasing
The process of translating a modulated signal to a higher or lower frequency while retaining all the originally transmitted information is
A. modulation
B. Frequency division
C. Frequency conversion
D. demodulation
What does standing-wave ratio mean?
A. The ratio of maximum to minimum voltages on a feed line
B. The ratio of maximum to minimum inductances on a feed line
C. The ratio of maximum to minimum resistances on a feed line
D. The ratio of maximum to minimum impedances on a feed line
For a transmission line with incident voltage Ei=5 V and reflected voltage Er=3 V, determine the reflection coefficient and the SWR.
A. 0.6; 4
B. 4; 0.6
C. 1.67; 0.25
D. 0.25; 1.67
Why is impedance matching important?
A. So the load will draw minimum power from the source
B. To ensure that there is less resistance than reactance in the circuit
C. To ensure that the resistance and reactance in the circuit are equal
D. So the source can deliver maximum power to the load
A frequency-selective circuit designed to pass some frequencies and reject others is a(n)
A. Tank circuit
B. filter
C. Harmonic circuit
D. Frequency doubler
Determine the physical length and characteristics impedance for a quarter-wavelength transformer that is used to match a section of RG-8 A❄U (Zo=50Ω) to a 150 Ω resistive load. The frequency of operation is 150 MHz, and the velocity factor Vf=1.
A. 1 m, 86.6 Ω
B. 2 m, 43.3 Ω
C. 1 m, 43.3 Ω
D. 2 m; 86.6 Ω
What does an SWR reading of less than 1.5:1 mean?
A. A fairly good impedance match
B. An impedance match which is too low
C. An impedance mismatch; something may be wrong with the antenna system
D. An antenna gain of 1.5
Indicate the noise whose source is in a category different from that of the other three.
A. Solar noise
B. Cosmic noise
C. Atmospheric noise
D. Galactic noise
Using TDR, a transmission line impairment is located 3000m from the source. For a velocity of propagation of 0.9c, determine the time elapsed from the beginning of the pulse to the reception of the echo.
A. 22.22 μs
B. 11.11 μs
C. 33.33 μs
D. 44.44 μs
What kind of SWR reading may mean poor electrical contact between parts of an antenna system?
A. A negative reading
B. No reading at all
C. A jumpy reading
D. A very low reading
Indicate the false statement.
A. HF mixers are generally noisier than HF amplifiers
B. Impulse noise voltage is independent of bandwidth
C. Thermal noise is independent of the frequency at which it is measured
D. Industrial noise is usually of the impulse type
A circuit that rejects or stops frequencies over a narrow range but allows frequencies above and below to pass is the
A. high-pass filter
B. Bandpass filter
C. band-reject filter
D. all-pass filter
Which of the following is the most reliable measurement for comparing amplifier noise characteristics?
A. signal-to-noise ratio
B. Noise factor
C. Shot noise
D. Thermal noise agitation
Find the characteristic impedance of each of the following line: a coaxial cable using a solid polyethylene dielectric having εr=2.3, with an inner conductor 2mm in diameter and an outer conductor 8mm in inside diameter.
A. 109.6 Ω
B. 54.8 Ω
C. 82.2 Ω
D. 164.4 Ω
What device might allow use of an antenna on a band it was not designed for?
A. An antenna tuner
B. An SWR meter
C. A low pass filter
D. A high pass filter
The signal attenuation in the passband of a filter is called
A. Insertion loss
B. roll-off loss
C. Notch loss
D. impedance
In a low-level AM system, amplifiers following the modulated stage must be
A. Linear devices
B. Harmonic devices
C. class C amplifiers
D. Nonlinear devices
Which of the following is also known as a notch filter?
A. low-pass
B. high-pass
C. bandpass
D. band-reject
The impedance of a coaxial line:
A. Can be the same for different diameter line
B. Changes with the frequency of the energy it carries
C. Is correct for only one size of line
D. Is greater for larger diameter line
What commonly available antenna feed line can be buried directly in the ground for some distance without adverse effects?
A. 300 ohm twin-lead
B. 600 ohm open-wire
C. 75 ohm twin-lead
D. Coaxial cable
Which of the following is not an advantage of an active filter?
A. gain
B. Easy to tune
C. Use of inductors
D. isolation
Which of the following statements is true?
A. Random noise power is inversely proportional to bandwidth
B. Flicker is sometimes called demodulation noise
C. Noise in mixers is caused by inadequate image frequency rejection
D. A random voltage across a resistance cannot be calculated
Which of the following filter is used to supply signals on exact frequencies with good stability?
A. RC low-pass
B. Bessel
C. crystal
D. LC notch
What does chirp mean?
A. A high-pitched tone which is received along with a CW signal
B. A small change in a transmitter's frequency each time it is keyed
C. A slow change in transmitter frequency as the circuit warms up
D. An overload in a receiver's audio circuit whenever CW is received
If the plate supply voltage for a plate-modulated class C amplifier is V, the maximum plate-cathode voltage could be almost as high as
A. 4V
B. 3V
C. 2V
D. 1V
Calculate the required Q for the situation for a 1MHz carrier and 80dB sideband suppression.
A. 12,500
B. 25,000
C. 125,000
D. 312,500
What can be done to keep a CW transmitter from chirping?
A. Add a key-click filter
B. Keep the power supply voltages very steady
C. Keep the power supply current very steady
D. missing
Which of the following filter is very small and inexpensive and widely used in communication transmitters and receivers?
A. Bessel
B. Butterworth
C. LC
D. ceramic
In a CW transmitter, the _______ is between the master oscillator and the power amplifier.
A. Audio amplifier
B. driver/buffer
C. Power supply
D. Telegraph key
An FM signal, 2000sin(2π×10^8t+2sinπ10^4 t)is applied to 50 ohm antenna. Determine the carrier frequency.
A. 2000Hz
B. 100MHz
C. 10kHz
D. None of the above
In a CW transmitter, the _______ controls when RF energy is applied to the antenna.
A. Master oscillator
B. driver/buffer
C. Telegraph key
D. Power amplifier
Which of the following is a fixed tuned bandpass filter that is designed to provide the exact selectivity required by a given application?
A. Bessel
B. Surface acoustic wave
C. Switched capacitor filters
D. ceramic
One of the following cannot be used to remove the unwanted sideband in SSB. This is the
A. Filter system
B. phase-shift method
C. Third method
D. Balanced modulator
Determine the modulation index to transmit an FM signal with fm=10kHz and a maximum deviation δ=20 kHz.
A. 2
B. 4
C. 6
D. 8
Vestigial sideband modulation (C3F) is normally used for
A. HF point-to-point communications
B. Monoaural broadcasting
C. TV broadcasting
D. Stereo broadcasting
When will a power source deliver maximum output to the load?
A. When air wound transformers are used instead of iron-core transformers
B. When the power-supply fuse rating equals the primary winding current
C. When the impedance of the load is equal to the impedance of the source
D. When the load resistance is infinite
To provide two or more voice circuits with the same carrier, it is necessary to use
A. ISB
B. Carrier insertion
C. SSB with pilot carrier
D. Lincompex
What happens when the impedance of an electrical load is equal to the internal impedance of the power source?
A. The electrical load is shorted
B. The source delivers maximum power to the load
C. No current can flow through the circuit
D. The source delivers minimum power to the load
The most commonly used filters in SSB generation are
A. mechanical
B. RC
C. LC
D. low-pass
Amplitude modulation by square waves or rectangular binary pulses is referred to as
A. phase-shift keying
B. amplitude-shift keying
C. frequency-shift keying
D. binary-shift keying
In an impedance smith chart, a clockwise movement along a constant resistance circle gives rise to
A. Decrease in the value of reactance
B. An increase in the value of reactance
C. No change in the reactance value
D. No change in the impedance value
What does an antenna matching unit do?
A. It matches a transceiver to a mismatched antenna system
B. It helps a receiver automatically tune in stations that are far away
C. It switches an antenna system to a transmitter when sending, and to a receiver when listening
D. It switches a transceiver between different kinds of antennas connected to one feed line
Indicate in which one of the following only one sideband is transmitted.
A. H3E
B. A3E
C. B8E
D. C3F
For an AM superheterodyne receiver that uses high- side injection and has a local oscillator frequency of 1355 kHz, determine the IF carrier, upper side frequency, and lower side frequency for an RF wave that is made up of a carrier and upper and lower side frequencies of 900 kHz, 905 kHz, and 895 kHz, respectively.
A. 455 kHz; 895 kHz; 905 kHz
B. 455 kHz; 460 kHz; 450 kHz
C. 455 kHz; 450 kHz; 900 kHz
D. 455 kHz; 10 kHz; 5 kHz
What would you use to connect a coaxial cable of 50 ohms impedance to an antenna of 35 ohms impedance?
A. An SWR meter
B. An impedance-matching device
C. A low pass filter
D. A terminating resistor
In amplitude modulation, how much of the transmitted power is in the carrier?
A. one-half
B. three-quarters
C. one-third
D. two-thirds
The difference between phase and frequency modulation
A. Is purely theoretical because they are the same in practice
B. Is too great to make the two system compatible
C. Lies in the poorer audio response of phase modulation
D. Lies in the different definitions of the modulation index
Double-sideband suppressed carrier signals are generated by a circuit called a
A. Balanced demodulator
B. Balanced modulator
C. Beat frequency oscillator
D. Notch filter
R3E modulation is sometimes used to
A. Allow the receiver to have a frequency synthesizer
B. Simplify the frequency stability problem in reception
C. Reduce the power that must be transmitted
D. Reduce the bandwidth required for transmission
What does an SWR reading of 1:1 mean?
A. The best impedance match has been attained
B. An antenna for another frequency band is probably connected
C. No power is going to the antenna
D. The SWR meter is broken
Which of the following is not a major benefit of SSB?
A. Noise in the signal is reduced
B. Conserves spectrum space
C. Less transmitter circuitry is used
D. More fading of an SSB signal over long distances
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