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107 Cards in this Set
- Front
- Back
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What type of jammer generates RF noise in a particular band or frequency channel to change the signal to noise ratio of a radar receiver? |
Spot Noise
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What are the operational pressures of high and low power dry air systems?
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25 to 35 psi high and 1 to 8 psi low
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What is the standard FM broadcast IF?
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10.7 Mhz
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What is dry air used in a waveguide for?
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To prevent arching
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What is reciprocity?
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The ability of an antenna to act as a transmitting or receiving antenna
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What is the hallmark of standard SSB?
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Long transmission range with minimal power use.
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When/why is the bandwidth of the NBFM communication system reduced?
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To accommodate signal and voice transmission.
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What does a type 1 dehydrator use to remove liquid and oil?
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Refrigerant
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What is the primary factor affecting radar accuracy?
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Radar system resolution
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The length of LOS is known as?
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Range
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What are the benefits of frequency synthesis?
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Smaller size, greater frequency stability, and versatility to interface with microprocessors
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What enables the HF system to communicate over long ranges?
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High power transmitters, sensitive receivers, and ionospheric conditions
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The maximum frequency just below the escape point?
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Critical frequency
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When the error voltage from the low pass filter ____ the VCO output frequency ______.
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Increases, Increases
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When intelligence is injected into the final RF power amplifier it is considered to be ______.
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High level modulation
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The higher the sun _____.
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The higher the frequency
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What form of SSB is commonly used in the military?
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ISB
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RF energy reflected from an object is called?
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Echo
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What is also a popular communications format with the U.S. Military?
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NBFM
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When are standing wave created?
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When there is an impedance mismatch in the transmission system.
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Where is the double conversion process used?
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In communication receivers
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What are the advantages of FM?
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Less interference between stations, greater noise suppression, and reduced transmitter power to cover an assigned area.
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The components of an AM signal are ____?
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USB, carrier, LSB
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What type of loss is due to high frequency currents flowing near the outer surface of the conductor?
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Skin effect loss
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What are FM sidebands that contain the majority of power called?
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Significant sidebands
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How many IF amplifier stages does a FM receiver normally have?
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2 or more
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Distortion is commonly caused by ____.
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Over driven amplifiers
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When a portion of electric energy is lost to the atmosphere, not a nearby object, it is called?
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Radiation loss
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What radar receiver circuit produces the IF frequency?
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The Mixer
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What is the most commonly used reference level in the decibel measurement system for RADAR?
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1 milliwatt
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To combat ECM use ____.
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ECCM
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The citizen band requency range is?
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26.965-27.405 Mhz
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What type of loss is due to the capacitance formed between transmission lines?
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Dielectric Loss
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If the VCO frequency is lagging the reference frequency; the DC error voltage?
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Increases
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What are noise spikes in FM removed by?
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The limiter
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The phase lock loop circuit is?
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A closed circuit
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A waveguide is defined as a system of material boundaries capable of guiding?
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Electromagnetic energy
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Why do radio wave have to be converted to sound waves?
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Electromagnetic waves have no effect on the human ear
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What form of SSB is used with television video signals?
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Vestibical sidebands
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True or False, FM receivers must have an RF amplifier?
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TRUE
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What form of SSB is commonly used by amateur radio operators?
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Standard SSB
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The local oscillator in the AM receivers is always tuned to?
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45 Khz above the tuned RF
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The bandwidth for NBFM is typically?
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10 Khz to 30 Khz
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What type of circuit demodulates FM signals according to frequency variations produced by the difference between the FM input frequency and VCO frequency?
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Phase lock loop
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The VCO frequency can lock onto the reference frequency when the reference signals is?
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Between the upper and lower cutoff frequency.
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Radio and light waves are ______ which are further classified as ________.
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Transverse waves, electromagnetic waves
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Adding a reflector to a horn antenna increases?
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Power gain and directivity
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What is RF energy reflected from an object called?
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Echo
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What is not a component of a typical communications systems?
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Satellite Up-link
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Why are some equipment enclosures hermatically sealed?
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To prevent the entrance of moisture
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How is electromagnetic energy produced?
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By current flowing through a conductor
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Which RADAR receiver component converts the IF pulses to video pulses?
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Video detector
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True or False; The AM receiver uses an RF amplifier?
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FALSE
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What type of an antenna would a RADAR system use to determine the bearing of an object?
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An antenna that has a narrow horizontal beam width
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Two objects at the same range must be separated by _____ to be separately distinguishable by the radar systems?
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At least one beam width
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What is the physical handling and installation of waveguides called?
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Plumbing
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The _____ the frequency wave, the more rapidly the wave is ______ by given degree of ionization?
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Lower, refracted
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A 30 Khz bandwidth is at the ______ end of normal bandwidth range?
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High
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Modulation may best be defined as?
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The superimposition of low frequency info on a high frequency carrier signal
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What is characteristic impedance?
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Distributed inductance and capacitance of the line
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Balanced modulators produced?
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Only the sum and difference
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Electromagnetic Energy is produced by ______.
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Current flowing through a conductor
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Effective suppression of the carrier requires?
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Highly matched components
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The RF Energy reflected from an object provides ____ to the radar system?
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Bearing, Range, Elevation, and Velocity
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The "B" dimensions determines the ______ handling capablity of a waveguide
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Power
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In frequency modulation the intelliegence is located in the ____.
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Frequency
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What does indirect synthesis use?
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PLL's and VCO's
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What terms are associated with the limiter?
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Threshold, Quieting, or Limiting Knee Voltage
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Incident traveling waves are?
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The RF signal traveling through a transmission line
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The input signals to the phase comparator are the?
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Reference signal and VCO signal
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The reference signal is applied to the ____.
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Phase comparator
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What is the purpose of the dust filter in the dry air system?
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To prevent desiccant and dust from contaminating the dry air system
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What is the main purpose of the HF system?
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To provide long range high frequency surface-to-surface, surface-to-air, and air-to-air radio communication
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What effect does FTC have on receiver gain?
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None
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How is an antennas power gain measured?
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In relation to a reference antenna
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Narrow-band FM is primarily used for
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Voice Communications
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What are the factors that influence Ionospheric refraction?
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Ionospheric density, transmitter operating frequency, and angle at which radio waves strike the ionosphere
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What is the least efficient type of equipment cooling?
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Convection
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What type of loss is due to resistance, respecially in long waves?
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Copper Loss
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True or False; Receivers may have more than one IF stage.
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True
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Frequency at which energy transmitted directly upward will escape directly into space?
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Escape point
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Each layer of the ionsphere has a maximum frequency that it will refract, known as the?
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Critical Frequency
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The heterodyning process creates?
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The original two frequency, their sum and difference
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The "A" dimension determines the _____ handling capabilty of a waveguide.
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Frequency
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What is the unit of measurement for radar?
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1 milliwatt
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Ceramic filters have a ____ response curve, but a ____ in gain.
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Sharp, Loss
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Which is an advantage of SSB transmission?
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Makes efficient use of the RF spectrum
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Superheterodyne is _______.
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The most commonly used in radar systems.
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The frequency at the output of the IF amp should be?
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455 KHz
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What is the filter's primary goal in PLL's?
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To remove the harmonic components of the refernece frequency.
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What is the definition of wave propagation?
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The movement of electromagnetic wave pass through a medium.
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The USB and LSB are always ____.
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180 degree out of phase
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Commonly caused by overdriven amplifiers?
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Distortion
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Where is a truncated parabolic antenna normally used?
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In a radar microwave system
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The length of the line of sight is ____.
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Range
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Demodulation occurs when the ____.
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"Intelligence" is extracted from the carrier.
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Selectivity is defined as ____.
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A receivers abilty to tune to a specific frequency while rejecting others
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The CW Jammer transmits _____ unmodulated jamming signals to change the signal-to-noise ratio of a radar receiver
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Constant - Amplitude , Constant - Frequency
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The frequency of a radio wave must be ____ to compensate for changes in the ionosphere during the day.
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Increased
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What is the maximum frequency that each inosphere will refract?
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Critical Frequency
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What is active ECM sometimes referred to as?
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Jamming
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Where is the intelligence in an AM signal located?
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Both in the sum of the original carrier and audio frequencies, and in the difference of the original carrier and audio frequencies.
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A type 1 dehydrator uses refigerant to remove _____.
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Liquid and Oil
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The primary system provides the initial source of coolling water that can either be ___.
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Seawater or chilled water
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The Secondary system transfers ___?
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The heat load from the electronic equipment
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Amplitude modulation may be defined as _____.
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Varying the carrier amplitude with the instantaneous changes of the audio signal
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The FM receiver's ability to select the stronger of the 2 signals with the same frequency is known as _____.
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The Capture Effect
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