1-50 If E_{m} and _{Ec} in the equation are assumed to represent peak-to-peak values, the following formula results: Since the peak-to-peak value of Emin figure 1-42 is e_{max}-e_{min}, we can substitute as follows: Also, since the peak-to-peak value of the carrier E_{c} is 2 times e_{o}, we can subsititute 2e_{o} for E_{c} as follows: Linear vertical distance represents voltage on the screen of a cathode-ray tube. Vertical distance units can be used in place of voltage in equations. Thus, if only the percent of modulation is required, the oscilloscope need not be calibrated and the actual circuit voltages are not required. In figure 1-42, e_{max}represents 600 volts (3 large divisions); e_{min} is 200 volts (1 division); and e_{o} is 400 volts (2 divisions). Using the equation and the dimensions of the screen pattern, you can figure the percent of modulation as follows: When e_{o} of the equation is difficult to measure, an alternative solution can be obtained with the equation below: VECTOR ANALYSIS OF AN AM WAVE.—You studied earlier in this chapter that the modulation envelope results when the instantaneous sums of the carrier and sideband voltages are plotted with respect to time. An attempt to add these three voltages, point-by-point, would prove to be a huge task. The same end result can be obtained by using a rotating vector to represent each of the three

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