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NAVEDTRA 14184A

MODULATION CH 1,2 ET2 BIB MAR 2017

QuestionAnswer
Which year was the first practical telegraph established in London, England? 1838
Which year did Marconi demonstrate the first practical wireless transmitter? 1897
Which year was the first successful transatlantic transmissions achieved? 1902
What is the ability to impress intelligence upon a transmission media? modulation
What is the mixing of two frequencies across a nonlinear impedance known as? heterodyning
What is the basic alternating waveform for all complex waveforms? sine wave
What is generated by rotating a coil in the magnetic field between two magnets? alternating current
What indicates how much of a cycle has been completed at any give time? phase angle
What is the ability known as to faithfully reproduce the input in the output? fidelity
What is the minimum frequency range that can be used for the transmission of speech? 500 to 2000Hz
In the modulation process, waves from the information source are impressed onto a radio-frequency sine wave called a what? carrier
What is an information wave normally referred to as? modulating wave
Output rises and falls directly with the input in which type of devices? linear
Which type of impedance is one in which the resulting current is not directly proportional to the change in the applied voltage? nonlinear
What is the sum of two individual sine waves? complex waveform
What is the process of combining two or more frequencies in a nonlinear impedance which results in the production of new frequencies called? heterodyning
How can the heterodyning process be analyzed? spectrum analysis
What is the amount of the frequency spectrum that signals occupy known as? bandwidth
How many conditions must be met in a circuit for heterodyning to occur? 2
What refers to any method of varying the amplitude of an electromagnetic carrier frequency in accordance with the intelligence to be transmitted by the carrier? amplitude modulation
What is a radio-frequency wave suitable for modulation by the intelligence to be transmitted? carrier frequency
What is on-off keying referred to as when applied to a continuously oscillating radio-frequency source? CW signaling
What was the first type of modulation used? CW
What is a system of on-off keying developed for telegraph that is capable of passing intelligence over wire at an acceptable rate? Morse code
What is one of the best methods for keying amplifier stages in transmitters? Blocked-grid keying
Which type of transmission has a high degree of clarity under sever noise conditions, long-range operation, and narrow bandwidth? continuous wave
Oscillators are too unstable for direct frequency control in what type of transmitters? VHF and UHF
In practice, the multiplication factor is seldom larger than what in any one stage? five
What is an energy converter that changes sound energy into electrical energy? microphone
What has the largest voltage output for a given mechanical stress and is the most commonly used crystal in microphones? Rochelle salt
Crystal microphones are delicate and must be handled with care. Exposure to temperatures above what may permanently damage the crystal unit? 125 degrees F
An AM transmitter can be divided into what two major sections according to the frequencies at which they operate? RF and AF
What are all of the sum frequencies above the carrier spoken of collectively as? upper sideband
Which agency assigns carrier frequencies for radio stations in the standard broadcast band? FCC
The standard AM broadcast band starts at 535kHz and ends at what? 1605kHz
How many sidebands accompany a carrier wave which has been modulated by voice or music signals? 2
What generates unwanted sideband frequencies? overmodulation
Which two categories are modulator circuits usually placed into? high or low
What is the simplest modulator available which is also the easiest to adjust for proper operation? plate modulation
Which action in the plate modulator effectively changes an audio frequency to a different part of the frequency spectrum? heterodyning
What is widely used in portable and mobile equipment to reduce size and power requirements? control-grid modulator
Which type of modulation is the angle of a sine wave carrier varied by a modulating wave? angle
What is used in frequency modulation to shift the frequency of an oscillator at an audio rate? audio signal
What is used in all single channel, radiotelegraph systems that use automatic printing systems? frequency shift keying
Which modulating signal property controls the amount by which the frequency departs from the average? amplitude
What is frequency deviation divided by the frequency of the modulating signal called? modulation index
What modulates oscillator frequency in direct modulation? reactance tube
Multivibrators are limited to frequencies below about what? 1MHz
What is simply a diode, or PN junction, that is designed to have a certain amount of capacitance between junctions? varactor
What is used to calculate the number of significant sidebands existing in the waveform? modulation index
What is the maximum value of the transmitted pulse? peak power
What is the ratio of working time to total time for intermittently operated devices? duty cycle
What is the duration of time RF frequency is transmitted known as? pulse width (PW)
Most radar oscillators operate at pulse voltages between 5 and how many kilovolts? 20 kV
What is a pulse-forming network discharged by? spark gap
Which type of spark gap uses a trigger pulse to ionize the air between the contacts of the spark gap and to initiate the discharge of the pulse-forming network? fixed gap
What is the most common type of radar modulator? hydrogen thyratron
In military voice systems the bandwidth for voice signals is limited to 300 to 3000 Hz, requiring a sampling frequency of what? 8kHz
What is the simplest form of pulse modulation? pulse amplitude
What refers to a system in which the standard values of a quantized wave are indicated by a series of coded pulses? pulse-code modulation (PCM)
Created by: nng7294