Module 12 - Modulation Principles
Pages i,
1-1,
1-11,
1-21,
1-31,
1-41,
1-51,
1-61,
1-71,
2-1,
2-11,
2-21,
2-31,
2-41,
2-51,
2-61,
3-1,
3-11,
3-21,
3-31, AI-1, Index, 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 radio-frequency waves. 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
| - |
Matter, Energy,
and Direct Current |
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Alternating Current and Transformers |
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Circuit Protection, Control, and Measurement |
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Electrical Conductors, Wiring Techniques,
and Schematic Reading |
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Generators and Motors |
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Electronic Emission, Tubes, and Power Supplies |
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Solid-State Devices and Power Supplies |
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Amplifiers |
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Wave-Generation and Wave-Shaping Circuits |
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Wave Propagation, Transmission Lines, and
Antennas |
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Microwave Principles |
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Modulation Principles |
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Introduction to Number Systems and Logic Circuits |
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- Introduction to Microelectronics |
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Principles of Synchros, Servos, and Gyros |
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Introduction to Test Equipment |
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Radio-Frequency Communications Principles |
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Radar Principles |
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The Technician's Handbook, Master Glossary |
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Test Methods and Practices |
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Introduction to Digital Computers |
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Magnetic Recording |
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Introduction to Fiber Optics |
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