Question

1. An AM receiver is tuned to broadcast station at 600 kHz. Calculate the image rejection in dB, assuming that the input filter consist of one tuned circuit with a Q of 40?
2. An SSB system transmit a peak envelope power of 100 W into a 75 ohms load. The carrier signal is modulated by two tones, with frequencies 2 kHz and 3 kHz with equal magnitude and only the lower sideband is transmitted with a suppressed carrier. Determine the average power into the load?
3. In the SSB, determine the maximum suppression of the unwanted sideband if the deviation from a perfect 90 phase shift is 5”?
4. An AM transmitter has an output power of 100 W at no modulation with efficiency of 60 %. What will be the output power with 97 % modulation?
5. Given an audio power of 500 W which will modulated an RF amplifier to 50 % modulate an RF amplifier to 50 % modulation. Find the DC power input?
6. A CB transmitter supplies a total power of 120 W to an aerial. Suppose the carrier is amplitude modulated to a depth of 80 %, how much power is wasted by the carrier signal?
7. Determine the modulation index of the signal given the following parameters: Emax = 10 Vp, Em= 4 Vp.
8. A DSB-SC system must suppress the carrier by 50 dB for its original value of 10 W. To what value must the carrier be reduced?
9. A transistor has a power dissipation rating of 30 W. Assuming that the transistor is the only element that dissipates power in a circuit, calculate the power an amplifier, using this transistor, could deliver the load if it operates as Class-A wit an efficiency of 30 %?
10. An AM signal supplies 150 W of carrier power when it is modulated by a single sine wave to a depth of 70 %. Suppose the total transmitted power increases by 10 % when another sine wave simultaneously amplitude modulates the carrier, determine the modulation index of the second sine wave?

Answer 1

Ans 1