9 Figure 1C. IN ANSWERING QUESTIONS 1-70 AND 1-71, REFER TO FIGURE 1C. 1-70. What is the phase relationship between the input signals fed to the diodes? 1. In phase 2. 90 degrees out of phase 3. 180 degrees out of phase 4. 270 degrees out of phase 1-71. A change in oscillator frequency will change which of the following input relationships between the sawtooth reference voltage and the incoming signal? 1. Phase 2. Voltage 3. Current 4. Amplitude 1-72. How is the long term stability and accuracy required of modern communications receivers attained? 1. Through the use of a single, crystal-controlled oscillator, as the local oscillator2. Through the use of an electron-coupled oscillator, as the local oscillator3. Through a process of automatic frequency control 4. Through a process known as frequency synthesis1-73. When using the frequency synthesisprocess, a signal of the desired accuracy and stability is produced by which, if any, of the following methods? 1. Automatic frequency control, that is, by sensing the difference between the oscillator frequency and the desired frequency and automatically compensating for this difference 2. Using a crystal-controlled oscillatorto produce a stable high frequency, and through the process of frequency division selecting a subharmonic of this frequency as the desired frequency 3. The heterodyning and selection of frequencies which are not harmonically related to each other 4. None of the above 1-74. Permanent magnet speakers respond quite well to which of the following audio frequency ranges? 1. Low 2. High 3. Mid band 4. Each of the above 1-75. For which of the following reasons do most standard Navy headphones respond poorly to low frequencies? 1. Small diaphragm size 2. Diaphragm inflexibility 3. Both 1 and 2 above 4. Input signal filtering
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