Principles of Communications
Midterm Exam
Name __________________________Schedule___________ Instructor ____________________
Instructions: Use up to four (4) decimal places. Print the problems and attached it on your answer sheets. Any erasures will not be given any credit.
#1. The frequencies of the AM broadcast transmitter ranges from 755 to 775 kHz. What is the value of the coil of the tuned oscillator if 4nF capacitor was used? Determine also the bandwith.
#2. A broadcast transmitter produces 4.5 kW in the sidebands when modulated at a level of 75%.
a. Under such conditions, how much carrier power does the transmitter have?
b. How much increase in antenna current would result by the 80% midulation if the antenna resistance is 500 Ohms?
#3. The antenna voltage of an AM broadcast transmitter, modulated to a depty of 45% by an audio sine wave is 30V. It increases to 33.75V as a result of simultaneous modulation by another audio sine wave. What is the modulation index due to this second wave?
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