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Electronic Communications

1. A microwave system requires a +4-dBm audio level to provide 100% modulation. Determine the voltage level required if this is a 600 ohm audio system.
2. Determine the noise produced by a 500 ohm resistor at 26 degrees Celcius over a 2 MHz bandwidth.
3. Consider an amplifier with an output of 2 mV rms and noise 0.76 mV rms. What is the signal to noise ratio? Express it as an absolute ratio and in dB.
4. Suppose that a series RLC circuit has R = 25 Ohm, L = 2 mH, and C = 0.8 microF. Compute the resonant frequency in kHz.
5. A filter has a bandwidth of 20 kHz and a peak output at 300 kHz. What is Q?
6. Calculate the percent modulation if the maximum p-p carrier in V is 200 and the minimum p-p is 40 V.
7. A 750 W carrier is modulated at an 85% level. Find the total transmitted power.
8. Consider a spectrum analyzer and suppose that V1 = 5 V, V2 = 0.1 V, V3 = 0.4 V, and V4 = 0.2 V. What is the total harmonic distortion?
9. For a certain AM signal, the fundamental is 3 V. If a harmonic at 4 kHz is 0.07 V, what is the relative harmonic distortion?
10. A 1 MHz 40-V peak carrier is modulated by a 5-kHz intelligence signal so that m = 0.7. This AM signal is fed to a 50 Ohm antenna. Calculate the power of each spectral component fed to the antenna.

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