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NAVEDTRA 14184A
MODULATION CH 1,2 ET2 BIB MAR 2017
Question | Answer |
---|---|
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) |