NEETS MOD 18 RADAR ASSIGNMENT 2
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- 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.
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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
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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.
- 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.