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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) |
Created by:
nng7294
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