Module 12 − Modulation Principles
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
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.
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.
The Emitter-INJECTION Modulator is an extremely low-level modulator that is useful in
The primary disadvantages of AM modulation are susceptibility to NOIsE INTERFERENCE and
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
two frequencies across a nonlinear impedance.
A-4. The process of recovering intelligence from a modulated
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.
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
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.
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.
One-half the amplitude of the carrier.
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.
cases when the use of a minimum of AF modulator power is desired.
A-46. Gain is
varied by changing the voltage on the emitter.
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
||Wave-Generation and Wave-Shaping Circuits
||Wave Propagation, Transmission Lines, and
||Introduction to Number Systems and Logic Circuits
||- Introduction to Microelectronics
||Principles of Synchros, Servos, and Gyros
||Introduction to Test Equipment
||Radio-Frequency Communications Principles
||The Technician's Handbook, Master Glossary
||Test Methods and Practices
||Introduction to Digital Computers
||Introduction to Fiber Optics
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