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71 Cards in this Set
- Front
- Back
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The action of impressing intelligence upon a transmission medium is referred to as
1. modulating 2. demodulating 3. heterodyning 4. wave generating |
modulating
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You can communicate with others using which of the following transmissions
mediums? 1. Light 2. Wire lines 3. Radio waves 4. Each of the above |
Each of the above
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When you use a vector to indicate force in a diagram, what do (a) length and (b) arrowhead position indicate?
1. (a) Magnitude (b) direction 2. (a) Magnitude (b) frequency 3. (a) Phase (b) frequency 4. (a) Phase (b) direction |
(a) Magnitude (b) direction
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Vectors are used to show which of the following characteristics of a sine wave?
1. Fidelity 2. Amplitude 3. Resonance 4. Distortion |
Amplitude
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A rotating coil in the uniform magnetic field between two magnets produces a
sine wave. It is called a sine wave because the voltage depends on which of the following factors? 1. The number of turns in the coil 2. The speed at which the coil is rotating 3. The angular position of the coil in the magnetic field 4. Each of the above |
The angular position of the coil in the magnetic field
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The trigonometric relationship for the sine of an angle in a right triangle is figured using which of the following ratios?
1. Opposite side ÷ hypotenuse 2. Adjacent side ÷ hypotenuse 3. Hypotenuse ÷ opposite side 4. Hypotenuse ÷ adjacent side |
Opposite side ÷ hypotenuse
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The part of a sine wave that is above the voltage reference line is referred to as the
1. peak amplitude 2. positive alternation 3. negative alternation 4. instantaneous amplitude |
peak amplitude
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The degree to which a cycle has been completed at any given instant is referred
to as the 1. phase 2. period 3. frequency 4. amplitude |
phase
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The frequency of the sine wave is determined by which of the following sine-wave factors?
1. The maximum voltage 2. The rate at which the vector rotates 3. The number of degrees of vector rotation 4. Each of the above |
The rate at which the vector rotates
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Which of the following mathematical relationships do you use to figure the period of a sine wave?
1.1/PHASE 3.1/DURATION 2.1/FREQUENCY 4.1/AMPLITUDE |
1/FREQUENCY
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Which of the following Greek letters is the symbol for wavelength?
1. θ 2. φ 3. λ 4. ω |
λ
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Which of the following waveform characteristics determines the wavelength
of a sine wave? 1. Phase 2. Period 3. Amplitude 4. Phase Angle |
Phase
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An electromagnetic wavefront moves through free space at approximately what speed in meters per second?
1. 3,000,000 2. 30,000,000 3. 300,000,000 4. 3,000,000,000 |
300,000,000
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What is the wavelength of a 1.5 MHz frequency?
1. 100 meters 2. 200 meters 3. 300 meters 4. 400 meters |
λ=(300,000,000 m/s)/(1,500,000 Hz) = 200 meters
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As the frequency of a signal is increased, what change can be noted about its wavelength?
1. It decreases 2. It increases 3. It remains the same |
It decreases
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The ability of a circuit to faithfully reproduce the input signal in the output is
known by what term? 1. Fidelity 2. Fluctuation 3. Directivity 4. Discrimination |
Fidelity
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In rf communications, modulation impresses information on which of the
following types of waves? 1. Carrier wave 2. Complex wave 3. Modulated wave 4. Modulating wave |
Carrier wave
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Which of the following types of modulation is a form of amplitude modulation?
1. Angle 2. Phase 3. Frequency 4. Continuous-wave |
Continuous-wave
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With a sine-wave input, how will the output compare to the input in (a) a linear
circuit and (b) a nonlinear circuit? 1. (a) Proportional (b) proportional 2. (a) Proportional (b) not proportional 3. (a) Not proportional (b) not proportional 4. (a) Not proportional (b) proportional |
(a) Proportional
(b) not proportional |
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What effect, if any, does a nonlinear device have on a sine wave?
1. It amplifies without distortion 2. It attenuates without distortion 3. It generates harmonic frequencies 4. None |
It generates harmonic frequencies
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For the heterodyning action to occur in a circuit, (a) what number of frequencies
must be present and (b) to what type of circuit must they be applied? 1. (a) Two (b) linear 2. (a) Two (b) nonlinear 3. (a) Three (b) nonlinear 4. (a) Three (b) linear |
(a) Two (b) nonlinear
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Spectrum analysis is used to view which of the following characteristics of an rf
signal? 1. Phase 2. Bandwidth 3. Modulating wave 4. Modulation envelope |
Bandwidth
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The method of rf communication that uses either the presence or absence of a carrier in a prearranged code is what type
of modulation? 1. Pulse modulation 2. Amplitude modulation 3. Continuous-wave modulation 4. Pulse-time modulation |
Amplitude modulation
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What is the purpose of the key in a cw transmitter?
1. It generates the rf oscillations 2. It heterodynes the rf oscillations 3. It controls the rf output 4. It amplifies the rf signal |
It controls the rf output
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To ensure frequency stability in a cw transmitter, you should NOT key what circuit?
1. The mixer 2. The detector 3. The oscillator 4. The rf amplifier |
The oscillator
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When keying a high-power transmitter, what component should you use to reduce the shock hazard?
1. A coil 2. A relay 3. A resistor 4. A capacitor |
A relay
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Interference detected by a receiver is often caused by the application and removal of power in nearby transmitters. This interference can be prevented by using what type of circuit in such transmitters?
1. Power filter 2. On-off filter 3. Key-click filter 4. Rf detector filter |
Key-click filter
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Transmitter machine keying was
developed for which of the following purposes? 1. To increase the speed of communications 2. To make communications more intelligible 3. To reduce interference 4. Each of the above |
To increase the speed of
communications |
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Which of the following advantages is a benefit of cw communications?
1. Wide bandwidth 2. Fast transmission 3. Long-range operation 4. Each of the above |
Long-range operation
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To prevent a transmitter from being loaded unnecessarily, where should you connect the antenna?
1. At the oscillator input 2. At the oscillator output 3. At the power-amplifier input 4. At the power-amplifier output |
At the power-amplifier output
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Amplifier tubes are added to the output of a transmitter for which of the following reasons?
1. To increase power 2. To increase frequency 3. To increase stability 4. To increase selectivity |
To increase power
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Which of the following combinations of frequency multiplier stages will produce
a total multiplication factor of 72? 1. 36, 36 2. 4, 3, 3, 2 3. 4, 4, 3, 2 4. 18, 18, 18, 18 |
4, 3, 3, 2
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To change sound energy into electrical energy, which of the following devices should you use?
1. A speaker 2. A microphone 3. An amplifier 4. An oscillator |
A microphone
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What component in a carbon microphone converts a dc voltage into a varying
current? 1. Button 2. Diaphragm 3. Transformer 4. Carbon granules |
Transformer
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The action of the double-button carbon microphone is similar to which of the
following electronic circuits? 1. A limiter 2. An oscillator 3. A voltage doulber 4. A push-pull amlifier |
A push-pull amlifier
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A carbon microphone has which of the following advantages over other types of
microphones? 1. Ruggedness 2. Sensitivity 3. Low output voltage 4. Frequency response |
Ruggedness
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The voltage produced by mechanical stress placed on certain crystals is a result
of which of the following effects? 1. Hall 2. Acoustic 3. Electrostatic 4. Piezoelectric |
Piezoelectric
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If you require a microphone that is lightweight, has high sensitivity, is rugged, requires no external voltage, can withstand temperature, vibration, and moisture extremes, and has a uniform
frequency response of 40 to 15,000 hertz, which of the following types of microphones should you select? 1. Carbon 2. Crystal 3. Dynamic 4. Electrostatic |
Dynamic
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What component in a magnetic
microphone causes the lines of flux to alternate? 1. The coil 2. The magnet 3. The diaphragm 4. The armature |
The diaphragm
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What are the two major sections of an AM transmitter?
1. Audio frequency unit and radio frequency unit 2. Audio frequency unit and master oscillator 3. Audio frequency unit and final power amplifier 4. Audio frequency unit and intermediate power amplifier |
Audio frequency unit and radio
frequency unit |
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The intermediate power amplifier serves what function in a transmitter?
1. It generates the carrier 2. It modulates the carrier 3. It increases the frequency of the signal 4. It increases the power level of the signal |
It increases the power level of the
signal |
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The final audio stage in an AM
transmitter is the 1. mixer 2. modulator 3. multipler 4. multiplexer |
modulator
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The vertical axis on a frequencyspectrum graph represents which of the
following waveform characteristics? 1. Phase 2. Duration 3. Frequency 4. Amplitude |
Frequency
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When a 500-hertz signal modulates a 1-megahertz carrier, the 1-megahertz
carrier and what two other frequencies are transmitted? 1. 500 and 999,500 hertz 2. 500 and 1,000,500 hertz 3. 999,500 and 1,500,000 hertz 4. 999,500 and 1,000,500 hertz |
500 and 1,000,500 hertz
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If 750 hertz modulates a 100-kilohertz carrier, what would the upper-sideband frequency be?
1. 99,250 hertz 2. 100,000 hertz 3. 100,500 hertz 4. 100,750 hertz |
100,750 hertz
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In an AM wave, where is the audio intelligence located?
1. In the carrier frequency 2. In the spacing between the sideband frequencies 3. In the spacing between the carrier and sideband frequencies 4. In the sideband frequencies |
In the sideband frequencies
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What determines the bandwidth of anb AM wave?
1. The carrier frequency 2. The number of sideband frequencies 3. The lowest modulating frequency 4. The highest modulating frequency |
The highest modulating frequency
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If an 860-kilohertz AM signal is modulated by frequencies of 5 and 10 kilohertz, what is the bandwidth?
1. 5 kilohertz 2. 10 kilohertz 3. 15 kilohertz 4. 20 kilohertz |
20 kilohertz
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If a 1-megahertz signal is modulated by frequencies of 50 and 75 kilohertz, what
is the resulting maximum frequency range? 1. 925,000 to 1,000,000 hertz 2. 925,000 to 1,075,000 hertz 3. 975,000 to 1,025,000 hertz 4. 1,000,000 to 1,075,000 hertz |
925,000 to 1,075,000 hertz
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If an rf carrier is 100 percent AM-modulated, what will be the rf output when the modulating signal is (a) at its negative peak and (b) at its positive peak?
1. (a) 0 (b) 2 times the amplitude of the unmodulated carrier 2. (a) 0 (b) 1/2 the amplitude of the unmodulated carrier 3.(a) 1/2 the amplitude of the unmodulated carrier (b) 1/2 the amplitude of the unmodulated carrier 4.(a) 1/2 the amplitude of the unmodulated carrier (b) 2 times the amplitude of the unmodulated carrier |
(a) 0
(b) 2 times the amplitude of the unmodulated carrier |
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In an AM signal that is 100 percent modulated, what maximum voltage value
is present in each sideband? 1. 1/4 the carrier voltage 2. 1/2 the carrier voltage 3. 3/4 the carrier voltage 4. Same as the carrier voltage |
1/2 the carrier voltage
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Overmodulation of an AM signal will have which, if any, of the following
effects on the bandwidth? 1. It will increase 2. It will decrease 3. It will remain the same |
It will remain the same
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In a carrier wave with a peak amplitude of 400 volts and a peak modulating voltage of 100 volts, what is the
modulation factor? 1. 0.15 2. 0.25 3. 0.45 4. 0.55 |
0.25
M=Em/Ec M=Mod factor Em=Pk-Pk mod voltage:100v Ec=Pk-Pk Carrier Voltage:400v |
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The percent of modulation for a modulated carrier wave is figured using which of the following formulas?
1.Em/Ec 3.Ec/Em 2.(Em/Ec)x100 4.(Ec/Em)x100 |
%M=(Em/Ec)x100
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Modulation produced in the plate circuit of the last radio stage of a system is
known by what term? 1. Low-level modulation 2. High-level modulation 3. Final-amplifier modulation 4. Radio frequency modulation |
High-level modulation
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Which, if any, of the following advantages is a primary benefit of plate
modulation? 1. It operates at low efficiency 2. It operates at low power levels 3. It operates with high efficiency 4. None of the above |
It operates with high efficiency
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A final rf power amplifier biased for plate modulation operates in what class of operation?
1. A 2. B 3. AB 4. C |
C
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A modulator power amplifier biased for plate modulation operates in what class
of operation? 1. A 2. B 3. AB 4. C |
A
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Heterodyning action in a plate modulator takes place in what circuit?
1. Grid 2. Plate 3. Screen 4. Cathode |
Plate
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A plate modulator produces a modulated rf output by controlling which of the
following voltages? 1. Plate voltage 2. Cathode voltage 3. Grid-bias voltage 4. Grid-input voltage |
Plate voltage
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To achieve 100-percent modulation in a plate modulator, what maximum voltage must the modulator tube be capable of providing to the final power amplifier
(fpa)? 1. Twice the fpa plate voltage 2. The same as the fpa plate voltage 3. Three times the fpa plate voltage 4. Half the fpa plate voltage |
Twice the fpa plate voltage
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In a plate modulator, with no modulation, how will the plate current of the final rf
amplifier appear on a scope? 1. A series of pulses at the carrier frequency 2. A series of pulses at twice the carrier frequency 3. A series of pulses at 1/4 the carrier frequency 4. A series of pulses at 1/2 the carrier frequency |
A series of pulses at the carrier frequency
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In the collector-injection modulator, af and rf are heterodyned by injecting the rf into (a) what circuit and the af into
(b) what circuit? 1. (a) Base (b) collector 2. (a) Base (b) emitter 3. (a) Emitter (b) collector 4. (a) Emitter (b) base |
(a) Base (b) collector
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Plate- and collector-injection modulators are the most commonly used modulators
for which of the following reasons? 1. The rf amplifier stages can be operated class C for linearity 2. The rf amplifier stages can be operated class C for maximum efficiency 3. They require small amounts of audio power 4. They require large amounts of audio power |
The rf amplifier stages can be
operated class C for maximum efficiency |
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A control-grid modulator would be used in which of the following situations?
1. In extremely high-power, wideband equipment where high-level modulation is difficult to achieve 2. In cases where the use of a minimum of audio power is desired 3. In portable and mobile equipment to reduce size and power requirements 4. Each of the above |
Each of the above
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Which of the following inputs is/are applied to the grid of a control-grid modulator?
1. Rf 2. Af 3. Dc bias 4. Each of the above |
Each of the above
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Excessive modulating signal levels have which, if any, of the following effects on
a control-grid modulator? 1. They increase output. amplitude 2. They decrease output amplitude 3. They create distortion 4. None |
They create distortion
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Compared to a plate modulator, the control-grid modulator has which of the
following advantages? 1. It is more efficient 2. It has less distortion 3. It requires less power from the modulator 4. It requires less power from the amplifier |
It requires less power from the modulator
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The control-grid modulator is similar to which of the following modulator circuits?
1. Plate 2. Cathode 3. Base-injection 4. Emitter-injection |
Base-injection
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A cathode modulator is used in which of the following situations?
1. When rf power is unlimited and distortion can be tolerated 2. When rf power is limited and distortion cannot be tolerated 3. When af power is unlimited and distortion can be tolerated 4. When af power is limited and distortion cannot be tolerated |
When rf power is limited and
distortion cannot be tolerated |
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In a cathode modulator, the modulating voltage is in series with which of the
following voltages? 1. The grid voltage only 2. The plate voltage only 3. Both the grid and plate voltages 4. The cathode voltage only |
Both the grid and plate voltages
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