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