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56 Cards in this Set

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