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Module 12 - Modulation Principles |
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Module 12 - Modulation Principles
Pages i - ix, 1-1 to 1-10, 1-11 to 1-20, 1-21 to 1-30, 1-31 to 1-40, 1-41 to 1-50, 1-51 to 1-60, 1-61 to 1-70, 1-71 to 1-75, 2-1 to 2-10, 2-11 to 2-20, 2-21 to 2-30, 2-31 to 2-40, 2-41 to 2-50, 2-51 to 2-60, 2-61 to 2-64, 3-1 to 3-10, 3-11 to 3-20, 3-21 to 3-30, 3-31 to 3-35, AI-1 to AI-6, Index-1 to 2, Assignment 1, 2
A COLLECTOR-INJECTION MODULATOR is a transistorized version of the plate modulator. It is classified as a high-level modulator, although present state-of-the-art transistors limit them to medium-power applications.
A CONTROL-GRID MODULATOR is a low-level modulator that is used where a minimum of AF modulator power is desired. It is less efficient than a plate modulator and produces more distortion. 1-71
A BASE-INJECTION MODULATOR is used to produce low-level modulation in equipment operating at very low power levels. It is often used in small portable equipment and test equipment.
The CATHODE MODULATOR is a low-level modulator employed where the audio power is limited and the inherent distortion of the grid modulator cannot be tolerated. 1-72
The EMITTER-INJECTION MODULATOR is an extremely low-level modulator that is useful in portable equipment.
The primary disadvantages of AM modulation are susceptibility to NOISE INTERFERENCE and the INEFFICIENCY of the transmitter. 1-73 ANSWERS TO QUESTIONS Q1. THROUGH Q46.
A-1. Modulation is the impressing of intelligence on a transmission medium. A-2. May be anything that
transmits information, such as light, smoke, sound, wire lines, or A-3. Mixing two frequencies across a nonlinear impedance. A-4. The process of recovering intelligence from a modulated carrier. A-5. The sine wave. A-6. To represent quantities that have both magnitude and direction. A-7. Sine θ = opposite side ÷ hypotenuse. A-8. e = Emax sine θ. A-9. The value at any given point on the sine wave. A-10. Phase or phase angle. A-11. The rate at which the vector which is generating the sine wave is rotating. A-12. The elapsed time from the beginning of cycle to its completion. A-13. Wavelength = rate of travel x period. A-14. Process of combining two signal frequencies in a nonlinear device. A-15. An impedance in which the resulting current is not proportional to the applied voltage. A-16. The display of electromagnetic energy that is arranged according to wavelength or frequency. A-17. At least two different frequencies applied to a nonlinear impedance. A-18. Any method of modulating an electromagnetic carrier frequency by varying its amplitude in accordance with the intelligence. A-19. A method of generating oscillations, a method of turning the oscillations on and off (keying), and an antenna to radiate the energy. A-20. Plate keying and cathode keying. A-21. Machine keying. A-22. A high degree of clarity even under severe noise conditions, long-range operation, and narrow bandwidth. A-23. Antenna-to-ground capacitance can cause the oscillator frequency to vary. A-24. To isolate the oscillator from the antenna and increase the amplitude of the RF oscillations to the required output level. A-25. To raise the low frequency of a stable oscillator to the vhf range. 1-74 A-26. An energy converter that changes sound energy into electrical energy. A-27. The changing resistance of carbon granules as pressure is applied to them. A-28. Background hiss resulting from random changes in the resistance between individual carbon granules. A-29. The piezoelectric effect. A-30. A dynamic microphone has a moving coil and the magnetic microphone has a moving armature. A-31. RF and AF units. A-32. 100 kilohertz, 5 kilohertz, 95 kilohertz, and 105 kilohertz. A-33. All of the sum frequencies above the carrier. A-34. The intelligence is contained in the spacing between the carrier and sideband frequencies. A-35. The highest modulating frequency. A-36. The depth or degree of modulation. A-37. One-half the amplitude of the carrier. A-38. A-39. Modulation produced in the plate circuit of the last radio stage of the system. A-40. Class C. A-41. Power amplifier. A-42. Between 0 and nearly two times its unmodulated value. A-43. Plate modulator. A-44. In cases when the use of a minimum of AF modulator power is desired. A-45. Low-level. A-46. Gain is varied by changing the voltage on the emitter. 1-75 NEETS Table of Contents
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