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

Module 12 − Modulation Principles

Pages i, 1−1, 1−111−21, 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


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.



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.


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.


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.


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.


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.


NEETS Modules
- Matter, Energy, and Direct Current
- Alternating Current and Transformers
- Circuit Protection, Control, and Measurement
- Electrical Conductors, Wiring Techniques, and Schematic Reading
- Generators and Motors
- Electronic Emission, Tubes, and Power Supplies
- Solid-State Devices and Power Supplies
- Amplifiers
- Wave-Generation and Wave-Shaping Circuits
- 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
Note: Navy Electricity and Electronics Training Series (NEETS) content is U.S. Navy property in the public domain.
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