ECEA111 Module 2 Exam Reviewer QUESTIONS: 1. How much is the % saving if R3E was used at m=0.8? = 87.89% 2. An AM wave has a total transmitted power of 4KW when modulated 85%. What is the total transmitted power if J3E was used instead? = 530.76 3. Anticipating single sideband AM, what percentage of the total power is saved by suppressing the carrier and one sideband while transmitting the other sideband only for m=0.75? = 89.02% 4. CB radios were developed using the full-carrier DSB AM. It operates using 40 channels, each 10KHz wide. When the SSBSC is used, the same carrier frequencies are used as with the conventional AM, but the trans-receivers are switchable to either lower or upper sideband. How may channels are available when the SSB is used? = 80 channels 5. If a transmitter power of 100W is sufficient for reliable communication over a certain path using the SSB, what is the power required for a double sideband full-carrier AM? = 600 W 6. An AM transmitter radiates 400W at 100% modulation. How much power is in the sidebands? = 133.33 W 7. An AM broadcast station operates at its maximum allowed total output of 50KW and at 85% modulation. How much is the % power of the carrier? = 73.46% 8. A 1000W carrier is to be modulated to a 90% level. Determine the total transmitted power. = 1405 W 9. If a transmitter supplies 8KW to the antenna when it is unmodulated, what is the total radiated power when it is modulated at 60%? = 9440 W 10. An AM DSBFC transmitter with an unmodulated carrier power, Pc=600Wthat is modulated simultaneously by four tones, m1= 0.1, m2= 0.2, m3= 0.4, and m4= 0.5, determine the total sideband power. = 137.9866 W 11. In the FCC emission designation, the first symbol indicates: - Nature of the modulating signal - Type of information - Type of modulation of main carrier - Type of communications media 12. What type of modulation is used to send the picture portion of a TV signal? - F3F - BBF - R3F - C3F 13. What is not an advantage of SSB Am over DSB AM? - Reduces bandwidth… - Reinforces the sideband… - Saves power… - More simple to generate… 14. To provide two or more voice circuits with the same carrier, it is necessary to use the - A3E - J3E - C3F - BBE 15. What is the circuit used to produced DSBSC AM? - Balanced modulator - Envelope detector - Amplitude modulator - Voltage controlled oscillator 16. Which of the following is a advantage of TRF receivers? - Sufficient image frequency rejection - Good sensitivity - Superior fidelity - Good selectivity 17. The output of a mixer is called - Image frequency - Baseband frequency - Carrier frequency - Intermediate frequency 18. Which part of the superheterodyne receiver provides the initial sensitivity - Pre-selector - Audio amplifier - Antenna - RF amplifier 19. The ability of a receiver to produce a faithful output with reference to the original information is called - Bass quality - Selectivity - Sensitivity - Fidelity 20. Which is not an example of receiver - Cr stereo - Cellular telephone - Microphone - TV 21. The higher the quality factor - Has no effect in IFRR - The higher the intermediate frequency - The higher the image frequency - The higher the IFRR 22. Heterodyning means - Doubing - Filtering - Mixing - Multiplicaton 23. Which of the ff. is true about image frequency when it is allowed to enter at the receiver? - Will produce usable demodulated signal - Always higher than the desired RF signal - Will produce undesired IF with no info - When mixed with local oscillator, will produce desired IF 24. An amplifier is used in receivers to improve… - Sensitivity - Shape factor - Fidelity - Selectivity 25. Which receiver component limits the image frequency from entering the mixer - Low pass audio filter - IF filter strips - Demodulator - Pre-selector 26. A receiver for a signal at 150 MHz uses a 10.7 MHz IF and low tracking. Calculate the LO frequency in MHz. = 139.3 MHz 27. For an IF frequency of 455 KHz, what must be the LO frequency (in KHz) when receiving a 580 KHz transmission? Assume high side injection. = 1035 KHz 28. A superheterodyne is tuned to 2738 KHz. The IF is 475 KHz. What is the image frequency in KHz? = 3688 KHz 29. For an AM receiver tuned to a station at 590 KHz with IF= 455 KHz, calculate the image frequency rejection in dB. Assume that the input filter consists of one tuned circuit with a Q of 40. = 38.6867 30. A superheterodyne receiver is tuned t a frequency of 5 MHz when the oscillator frequency is 6.85 MHz. What is the intermediate frequency in MHz? = 1.85 MHz
