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56 Cards in this Set
- Front
- Back
What is the purpose of the synchronizer in a radar system?
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Controls system operation and timing.
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What is the purpose of the majority of circuits in a radar system?
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Timing and control.
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A self-synchronized radar system obtains timing trigger pulses from what source?
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Transmitter.
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What type of multivibrator can be used as a radar master oscillator?
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Free-running.
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In an externally synchronized radar, what determines the prr of the transmitter?
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The master oscillator.
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What basic circuits meet the requirements of an externally synchronized master oscillator?
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Sine-wave oscillator, single-swing blocking oscillator, and master-trigger (astable) multivibrator.
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Name a disadvantage of sine-wave oscillator synchronizers.
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It requires additional shaping circuits.
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Which of the basic timing circuits produces sharp trigger pulses directly?
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Blocking oscillators.
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What are the two basic types of transmitters?
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Keyed oscillator and power-amplifier chain.
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What controls transmitter pulse width?
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The modulator.
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In addition to a flat top, what characteristics must a modulator pulse have?
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Steep leading and trailing edges.
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What is the purpose of the synchronizer in a radar system?
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Controls system operation and timing.
|
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What is the purpose of the majority of circuits in a radar system?
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Timing and control.
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A self-synchronized radar system obtains timing trigger pulses from what source?
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Transmitter.
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What type of multivibrator can be used as a radar master oscillator?
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Free-running.
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In an externally synchronized radar, what determines the prr of the transmitter?
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The master oscillator.
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What basic circuits meet the requirements of an externally synchronized master oscillator?
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Sine-wave oscillator, single-swing blocking oscillator, and master-trigger (astable) multivibrator.
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Name a disadvantage of sine-wave oscillator synchronizers.
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It requires additional shaping circuits.
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Which of the basic timing circuits produces sharp trigger pulses directly?
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Blocking oscillators.
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What are the two basic types of transmitters?
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Keyed oscillator and power-amplifier chain.
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What controls transmitter pulse width?
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The modulator.
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In addition to a flat top, what characteristics must a modulator pulse have?
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Steep leading and trailing edges.
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What type of modulator is most commonly used in modern radar systems?
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Line-pulsed.
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What three types of storage elements most often are used in modulators?
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Capacitor, artificial transmission line, or pulse-forming network.
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What characteristic is determined by the time required for a voltage wave to travel from the input end of an artificial transmission line to the output end and back again?
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Pulse width.
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What type of tube best meets the requirements of a modulator switching element?
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Thyratron.
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What modulator element controls the rate at which the storage element charges?
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The charging impedance.
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What is the frequency range of magnetron oscillators?
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600-30,000 megahertz.
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What two forms of instability are common in magnetrons?
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Mode skipping and mode shifting.
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What is the effect on magnetron operation if the magnetic field strength is too high?
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The magnetron will not oscillate.
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What is the typical frequency range about the center frequency of a tunable magnetron?
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±5 percent.
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What is the primary advantage of power-amplifier transmitters over keyed-oscillator
transmitters? |
Frequency stability.
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What type of klystron is used as the final stage of a power-amplifier transmitter?
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Multicavity klystron.
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What transmitter component allows the radiation of a large number of discrete frequencies over a wide band?
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Frequency synthesizer.
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What is the result of pulsing a pulsed rf amplifier when no rf is present?
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Oscillations at an undesired frequency.
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What type of switches are used as duplexers?
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Electronic.
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What tube in a duplexer has the primary function of disconnecting the receiver?
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Tr tube.
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How may the tr tube ionization speed be increased?
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Apply keep-alive voltage.
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The actions of the tr and atr circuits depend on the impedance characteristics of what length of transmission line?
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Quarter-wavelength section.
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During which of the transmit or receive cycles are both the tr and atr tubes of a parallel-connected duplexer ionized (arcing)?
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Transmit.
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In a series-connected duplexer, what tube (tr or atr), if any, fires during the receive cycle?
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Neither fires.
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To propagate energy down an arm of a hybrid ring duplexer, the two fields at the junction of the arm and the ring must have what phase relationship?
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180 degrees out of phase.
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What is the greatest limiting factor in a receiver’s detectable range?
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Noise.
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What type of receiver is most often used in radar systems?
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Superheterodyne.
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What IF frequencies are normally used in radar receivers?
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Thirty or sixty megahertz.
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Which component of the receiver produces the signal that is mixed with the received signal to produce the IF signal?
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Local oscillator.
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What receiver circuit actually produces the IF frequency?
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Mixer.
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The IF amplifiers are connected in what amplifier configuration?
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Cascade
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Which receiver component converts the IF pulses to video pulses?
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Detector.
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Which of the two types of automatic gain control, agc or iagc, is most effective in radar use for the Navy?
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IAGC.
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Immediately after the transmitter fires, stc reduces the receiver gain to what level?
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Zero.
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How does ftc affect receiver gain, if at all?
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FTC has no effect on receiver gain.
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What type of target has a fixed phase relationship from one receiving period to the next?
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Stationary
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What signal is used to synchronize the coherent oscillator to a fixed phase relationship with the
transmitted pulse? |
Coho lock pulse.
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What is the phase relationship between the delayed and undelayed video?
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Opposite.
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When a large signal and a small signal are applied to a lin-log amplifier at the same time, what is the effect on the small signal?
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Amplification is reduced.
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