Subelement H: Modulation— Topic 58: SSB Modulation
Question 3-58H5
Element 3 (GROL)How can a double-sideband phone signal be produced?
Explanation
A double-sideband (DSB) phone signal is characteristic of Amplitude Modulation (AM). Modulating the supply voltage to a Class C amplifier (or any RF amplifier) is a direct method to achieve AM. As the audio input varies the amplifier's supply voltage, the output RF power (and thus its amplitude) changes proportionally. This amplitude variation creates both an upper and a lower sideband around the carrier frequency, resulting in a DSB signal.
Options A and B describe methods of producing Frequency Modulation (FM) by varying an oscillator's frequency. FM signals have constant amplitude. Option C describes a Phase-Locked Loop (PLL), primarily used for frequency control or demodulation, not for directly generating an amplitude-modulated DSB signal.
Related Questions
3-58H3 What kind of input signal could be used to test the amplitude linearity of a single-sideband phone transmitter while viewing the output on an oscilloscope?3-58H4 What does a two-tone test illustrate on an oscilloscope?3-58H6 What type of signals are used to conduct an SSB two-tone test?3-59H1 What is an important factor in pulse-code modulation using time-division multiplex?3-59H2 In a pulse-width modulation system, what parameter does the modulating signal vary?