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Navy Electricity and Electronics Training Series (NEETS)
Module 12—Modulation Principles
Chapter 1:  Pages 1-71 through 1-75

 


Cathode modulator



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.

 

Collector-injection modulator

 


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


 


Control-grid modulator



 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.

Base-injectino modulator



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




Cathode modulator



The EMITTER-INJECTION MODULATOR is an extremely low-level modulator that is useful in portable equipment.

Emitter-injection modulator



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 &divide; 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.
Formula - RF Cafe

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



Introduction to Matter, Energy, and Direct Current, Introduction to Alternating Current and Transformers, Introduction to Circuit Protection, Control, and Measurement, Introduction to Electrical Conductors, Wiring Techniques, and Schematic Reading, Introduction to Generators and Motors, Introduction to Electronic Emission, Tubes, and Power Supplies, Introduction to Solid-State Devices and Power Supplies, Introduction to Amplifiers, Introduction to Wave-Generation and Wave-Shaping Circuits, Introduction to Wave Propagation, Transmission Lines, and Antennas, Microwave Principles, Modulation Principles, Introduction to Number Systems and Logic Circuits, Introduction to Microelectronics, Principles of Synchros, Servos, and Gyros, Introduction to Test Equipment, Radio-Frequency Communications Principles, Radar Principles, The Technician's Handbook, Master Glossary, Test Methods and Practices, Introduction to Digital Computers, Magnetic Recording, Introduction to Fiber Optics

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