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2009 Element 8 pool
60 / 300 questions need explanations
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In a RADAR receiver AGC and IAGC can vary between:
  • 10 and 15 db. (9% chose this)
  • 20 and 40 db. (46% chose this)
  • 30 and 60 db. (25% chose this)
  • 5 and 30 db. (20% chose this)
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Pulse-forming networks are usually composed of the following:
  • Series capacitors and shunt inductors. (18% chose this)
  • Series inductors and shunt capacitors. (43% chose this)
  • Resonant circuit with an inductor and capacitor. (29% chose this)
  • None of the above. (10% chose this)
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What component of a RADAR receiver is represented by block 49 in Fig. 8A1?
  • Discriminator. (23% chose this)
  • IF amplifier. (8% chose this)
  • Klystron. (19% chose this)
  • Crystal detector (the mixer). (50% chose this)
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A defective crystal in the AFC section will cause:
  • No serious problems. (1% chose this)
  • Bright flashing pie sections on the PPI. (50% chose this)
  • Spiking on the PPI. (13% chose this)
  • Vertical spikes that constantly move across the screen. (37% chose this)
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While the vessel is docked the presentation of the pier is distorted near the center of the PPI with the pier appearing to bend in a concave fashion. This is a primary indication of what?
  • The deflection coils need adjusting. (22% chose this)
  • The centering magnets at the CRT neck need adjusting. (17% chose this)
  • The waveguide compensation delay line needs adjusting. (52% chose this)
  • The CRT filaments are weakening. (9% chose this)
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RADAR interference on a communications receiver appears as:
  • A varying tone. (14% chose this)
  • Static. (22% chose this)
  • A hissing tone. (11% chose this)
  • A steady tone. (53% chose this)
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To insert RF energy into or extract RF energy from a waveguide, which of the following would not be used?
  • Coupling capacitance. (52% chose this)
  • Current loop. (9% chose this)
  • Aperture window. (16% chose this)
  • Voltage probe. (23% chose this)
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An RF mixer has what purpose in a RADAR system?
  • Mixes the CW transmitter output to form pulsed waves. (16% chose this)
  • Converts a low-level signal to a different frequency. (53% chose this)
  • Prevents microwave oscillations from reaching the antenna. (11% chose this)
  • Combines audio tones with RF to produce the RADAR signal. (20% chose this)
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Which of the following statements about antenna resolvers is correct?
  • Most resolvers contain a rotor winding and a delta stator winding. (10% chose this)
  • Resolvers consist of a two rotor windings and two stator windings that are 90 degrees apart. (27% chose this)
  • The basic resolver contains a rotor winding and two stator windings that are 90 degrees apart. (52% chose this)
  • Resolvers consist of a "Y" connected rotor winding and a delta connected stator winding. (11% chose this)
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In a RADAR unit, if the crystal mixer becomes defective, replace the:
  • Crystal only. (7% chose this)
  • The crystal and the ATR tube. (18% chose this)
  • The crystal and the TR tube. (55% chose this)
  • The crystal and the klystron. (19% chose this)
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A circuit card in a RADAR system has just been replaced with a spare card. You notice the voltage level at point E in Fig. 8F12 is negative 4.75 volts when the inputs are all at 5 volts. The problem is:
  • The 25 K resistor is open. (11% chose this)
  • The 100 K resistor has been mistakenly replaced with a 50 K resistor. (14% chose this)
  • The op amp is at the rail voltage. (10% chose this)
  • The 50 K resistor has been mistakenly replaced with a 25 K resistor. (64% chose this)
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Which of the following statements is true?
  • The front end of the receiver does not provide any amplification to the RADAR signal. (58% chose this)
  • The mixer provides a gain of at least 6 db. (6% chose this)
  • The I.F. amplifier is always a high gain, narrow bandwidth amplifier. (24% chose this)
  • None of the above. (13% chose this)
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An antenna synchro transmitter is composed of the following:
  • Three rotor and two stator windings. (15% chose this)
  • Two rotor and three stator windings. (55% chose this)
  • Three rotor and three stator windings. (11% chose this)
  • A single rotor and 3 stator windings. (19% chose this)
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In the receive mode, frequency conversion is generally accomplished by a:
  • Tunable wave-guide section. (16% chose this)
  • Pentagrid converter. (11% chose this)
  • Crystal diode. (64% chose this)
  • Ferrite device. (9% chose this)
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What component of a RADAR receiver is represented by block 48 in Fig. 8A1?
  • Klystron (local oscillator). (59% chose this)
  • Discriminator. (23% chose this)
  • IF amplifier. (9% chose this)
  • Crystal detector. (10% chose this)
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In the circuit contained in Fig. 8F12, there are 5 volts present at points B and C, and there are zero volts present at points A and D. What is the voltage at point E?
  • -1.5 Volts. (58% chose this)
  • 3.75 Volts. (24% chose this)
  • 23.75 Volts. (7% chose this)
  • 4.5 Volts. (12% chose this)
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The klystron local oscillator is constantly kept on frequency by:
  • Constant manual adjustments. (2% chose this)
  • The Automatic Frequency Control circuit. (62% chose this)
  • A feedback loop from the crystal detector. (22% chose this)
  • A feedback loop from the TR box. (14% chose this)
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The primary cause of noise in a RADAR receiver can be attributed to:
  • Electrical causes. (7% chose this)
  • Atmospheric changes. (16% chose this)
  • Poor grounding. (17% chose this)
  • Thermal noise caused by RADAR receiver components. (61% chose this)
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Video amplifiers in pulse RADAR receivers must have a broad bandwidth because:
  • Weak pulses must be amplified. (63% chose this)
  • High frequency sine waves must be amplified. (6% chose this)
  • The RADARs operate at PRFs above 100. (8% chose this)
  • The pulses produced are normally too wide for video amplification. (23% chose this)
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On a basic synchro system, the angular information is carried on the:
  • DC feedback signal. (11% chose this)
  • Stator lines. (57% chose this)
  • Deflection coils. (16% chose this)
  • Rotor lines. (16% chose this)
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When monitoring the gate voltage of a power MOSFET in the switching power supply of a modern RADAR, you would expect to see the gate voltage change from "low" to "high" by how much?
  • 1 volt to 2 volts. (20% chose this)
  • 300 microvolts to 700 microvolts. (9% chose this)
  • Greater than 2 volts. (64% chose this)
  • 1.0 volt to 20.0 volts. (7% chose this)
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The primary operating frequency of a reflex klystron is controlled by the:
  • Dimensions of the resonant cavity. (58% chose this)
  • Level of voltage on the control grid. (10% chose this)
  • Voltage applied to the cavity grids. (8% chose this)
  • Voltage applied to the repeller plate. (24% chose this)
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In the circuit shown in Fig. 8A6, which of the following is true?
  • With A and B high, Q1 is saturated and Q2 is off. (28% chose this)
  • With either A or B low, Q1 is saturated and Q2 is off. (57% chose this)
  • With A and B low, Q2 is on and Q4 is off. (8% chose this)
  • With either A or B low, Q1 is off and Q2 is on. (8% chose this)
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What device(s) could be used as the local oscillator in a RADAR receiver?
  • Thyratron (6% chose this)
  • Klystron (22% chose this)
  • Klystron and a Gunn Diode (64% chose this)
  • Gunn diode (8% chose this)
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The phantastron circuit is capable of:
  • Stabilizing the magnetron. (12% chose this)
  • Preventing saturation of the RADAR receiver. (17% chose this)
  • Being used to control repeller voltage in the AFC system. (15% chose this)
  • Developing a linear ramp voltage when triggered by an external source. (56% chose this)
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The following is true concerning waveguides:
  • Conduction is accomplished by the polarization of electromagnetic and electrostatic fields. (22% chose this)
  • Ancillary deflection is employed. (2% chose this)
  • The magnetic field is strongest at the center of the waveguide. (14% chose this)
  • The magnetic field is strongest at the edges of the waveguide. (62% chose this)
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The modulation frequency of most RADAR systems is between:
  • 60 and 500 Hz. (63% chose this)
  • 3000 and 6000 Hz. (8% chose this)
  • 1500 and 7500 Hz. (13% chose this)
  • 1000 and 3000 Hz. (16% chose this)
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How many sequential memory cells with target returns are required to display the target?
  • 1 (2% chose this)
  • 2 (66% chose this)
  • 4 (21% chose this)
  • 8 (11% chose this)
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A Gunn diode oscillator takes advantage of what effect?
  • Negative resistance. (20% chose this)
  • Avalanche transit time. (10% chose this)
  • Bulk-effect. (11% chose this)
  • Negative resistance and bulk-effect. (60% chose this)
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Waveguide theory is based on the principals of:
  • Ohm's Law. (13% chose this)
  • High standing waves. (7% chose this)
  • Skin effect and use of ΒΌ wave stubs. (68% chose this)
  • None of the above. (12% chose this)
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How is the variable range marker usually adjusted for accuracy?
  • Adjusting the frequency of the VRM oscillator at the maximum range. (17% chose this)
  • Adjusting the frequency of the VRM oscillator at the minimum range. (4% chose this)
  • Adjusting the readout to match at the median range ring. (8% chose this)
  • The minimum and maximum ranges are aligned with the matching fixed range ring. (71% chose this)
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Which is typical current for a silicon crystal used in a RADAR mixer or detector circuit?
  • 3 mA (63% chose this)
  • 15 mA (12% chose this)
  • 50 mA (20% chose this)
  • 100 mA (6% chose this)
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The indicated distance from your own vessel to a lighthouse is found to be in error. What circuit would you suspect?
  • Range ring oscillator. (67% chose this)
  • Video amplifier. (3% chose this)
  • STC circuit. (19% chose this)
  • FTC circuit. (12% chose this)
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In the circuit shown in Fig. 8A4, U5 pins 1 and 4 are high and both are in the reset state. Assume one clock cycle occurs of Clk A followed by one cycle of Clk B. What are the output states of the two D-type flip flops?
  • Pin 5 low, Pin 9 low. (17% chose this)
  • Pin 5 high, Pin 9 low. (9% chose this)
  • Pin 5 low, Pin 9 high. (9% chose this)
  • Pin 5 high, Pin 9 high. (65% chose this)
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RADAR antenna direction must be sent to the display in all ARPAs or RADAR systems. How is this accomplished?
  • 3-phase synchros. (15% chose this)
  • 2-phase resolvers. (11% chose this)
  • Optical encoders. (7% chose this)
  • Any of the above. (68% chose this)
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The usual intermediate frequency of a shipboard RADAR unit is:
  • 455 kHz. (11% chose this)
  • 10.7 MHz. (9% chose this)
  • 30 or 60 MHz. (71% chose this)
  • 120 MHz. (9% chose this)
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Which of the following is not part of the transmitting system?
  • Magnetron. (7% chose this)
  • Modulator. (9% chose this)
  • Pulse Forming Network. (16% chose this)
  • Klystron. (68% chose this)
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The center of the transmitted lobe from a slotted waveguide array is:
  • Several degrees offset from a line perpendicular to the antenna. (68% chose this)
  • Perpendicular to the antenna. (29% chose this)
  • Maximum at the right hand end. (1% chose this)
  • Maximum at the left hand end. (2% chose this)
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In a RADAR unit, the mixer uses a:
  • Pentagrid converter tube. (5% chose this)
  • Field-effect transistor. (12% chose this)
  • Silicon crystal or PIN diode. (76% chose this)
  • Microwave transistor. (8% chose this)
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In a raster-type display, the electron beam is scanned:
  • From the center of the display to the outer edges. (12% chose this)
  • Horizontally and vertically across the CRT face. (72% chose this)
  • In a rotating pattern which follows the antenna position. (10% chose this)
  • From one specified X-Y coordinate to the next. (6% chose this)
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In a solid-state RADAR modulator, the duration of the transmitted pulse is determined by:
  • The thyratron. (13% chose this)
  • The magnetron voltage. (9% chose this)
  • The pulse forming network. (70% chose this)
  • The trigger pulse. (9% chose this)
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When comparing a TTL and a CMOS NAND gate:
  • Both have active pull-up characteristics. (72% chose this)
  • Both have three output states. (4% chose this)
  • Both have comparable input power sourcing. (11% chose this)
  • Both employ Schmitt diodes for increased speed capabilities. (13% chose this)
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A negative voltage is commonly applied to the magnetron cathode rather than a positive voltage to the magnetron anode because:
  • The cathode must be made neutral to force electrons into the drift area. (11% chose this)
  • A positive voltage would tend to nullify or weaken the magnetic field. (9% chose this)
  • The anode can be operated at ground potential for safety reasons. (71% chose this)
  • The cavities might not be shock-excited into oscillation by a positive voltage. (9% chose this)
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One of the best methods of reducing noise in a RADAR receiver is?
  • Changing the frequency. (9% chose this)
  • Isolation. (79% chose this)
  • Replacing the resonant cavity. (12% chose this)
  • Changing the IF strip. (1% chose this)
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What is the main difference between an analog and a digital receiver?
  • Special amplification circuitry. (1% chose this)
  • The presence of decision circuitry to distinguish between "on" and "off" signal levels. (80% chose this)
  • An AGC stage is not required in a digital receiver. (5% chose this)
  • Digital receivers produce no distortion. (14% chose this)
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The anode of a magnetron is normally maintained at ground potential:
  • Because it operates more efficiently that way. (9% chose this)
  • For safety purposes. (75% chose this)
  • Never. It must be highly positive to attract the electrons. (8% chose this)
  • Because greater peak-power ratings can be achieved. (8% chose this)
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In a RADAR unit, the mixer uses:
  • PIN diodes and silicon crystals. (79% chose this)
  • PIN diodes. (7% chose this)
  • Boettcher crystals. (2% chose this)
  • Silicon crystals. (12% chose this)
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How is the signal removed from a waveguide or magnetron?
  • With a thin wire called a T-hook. (5% chose this)
  • With a thin wire called a J-Hook. (79% chose this)
  • With a coaxial connector. (7% chose this)
  • With a waveguide flange joint. (9% chose this)
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Noise can appear on the LCD as:
  • Erratic video and sharp changes in intensity. (76% chose this)
  • Black spots on the screen. (11% chose this)
  • Changes in bearings. (4% chose this)
  • None of the above. (10% chose this)
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Prior to making "power-on" measurements on a switching power supply, you should be familiar with the supply because of the following:
  • You need to know where the filter capacitors are so they can be discharged. (11% chose this)
  • If it does not use a line isolation transformer you may destroy the supply with grounded test equipment. (79% chose this)
  • It is not possible to cause a component failure by using ungrounded test equipment. (6% chose this)
  • So that measurements can be made without referring to the schematic. (4% chose this)
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At microwave frequencies, waveguides are used instead of conventional coaxial transmission lines because:
  • They are smaller and easier to handle. (5% chose this)
  • They have considerably less loss. (79% chose this)
  • They are lighter since they have hollow centers. (4% chose this)
  • Moisture is never a problem with them. (13% chose this)
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Sea return is:
  • Sea water that gets into the antenna system. (0% chose this)
  • The return echo from a target at sea. (17% chose this)
  • The reflection of RADAR signals from nearby waves. (80% chose this)
  • None of the above. (3% chose this)
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Low or no mixer current could be caused by:
  • Local oscillator frequency misadjustment. (8% chose this)
  • TR cell failure. (12% chose this)
  • Mixer diode degradation. (3% chose this)
  • All of the above. (77% chose this)
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A rotary joint is used to:
  • Couple two waveguides together at right angles. (9% chose this)
  • Act as a switch between two waveguide runs. (7% chose this)
  • Connect a stationary waveguide to the antenna array. (76% chose this)
  • Maintain pressurization at the end of the waveguide. (8% chose this)
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The basic frequency determining element in a Gunn oscillator is:
  • The power supply voltage. (7% chose this)
  • The type of semiconductor used. (6% chose this)
  • The resonant cavity. (74% chose this)
  • The loading of the oscillator by the mixer. (14% chose this)
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The term DRAM stands for:
  • Digital refresh access memory. (4% chose this)
  • Digital recording access memory. (4% chose this)
  • Dynamic random access memory. (92% chose this)
  • Digital response area motion. (0% chose this)
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A basic sample-and-hold circuit contains:
  • An analog switch and an amplifier. (3% chose this)
  • An analog switch, a capacitor, and an amplifier. (14% chose this)
  • An analog multiplexer and a capacitor. (3% chose this)
  • An analog switch, a capacitor, amplifiers and input and output buffers. (80% chose this)
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What is the most common type of RADAR antenna used aboard commercial maritime vessels?
  • Parabolic. (6% chose this)
  • Truncated parabolic. (3% chose this)
  • Slotted waveguide array. (91% chose this)
  • Multi-element Yagi array. (1% chose this)
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Blocking oscillators operate on the formula of:
  • T = R x C. (78% chose this)
  • I = E/R. (4% chose this)
  • By using the receiver's AGC. (9% chose this)
  • None of the above are correct. (9% chose this)
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Silicon crystals:
  • Are very sensitive to static electric charges. (11% chose this)
  • Should be wrapped in lead foil for storage. (3% chose this)
  • Tolerate very low currents. (2% chose this)
  • All of these. (84% chose this)
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