Radio and Fm Broadcast Transmitter

November 28, 2017 Engineering

QUIZ # 2 ECP433L1 Direction: Rewrite the following questions in Engineering Lettering before answering. This will be send by 10:30 am.. Therefore call time for papers is 4. 30 in the afternoon. Scan or photos of the papers will be send in my email. Thanks PS.. 1. Determine the percent modulation of an AM for the following conditions if the unmodulated carrier is 80 V peak to peak. | Maximum P-P carrier| Minumum P-P carrier| (a)| 100| 60| (b)| 125| 35| (c)| 160| 0| (d)| 180| 0| (e)| 135| 35| 2. Determine the maximum sideband power if the carrier output is 1 kW and calculate the total maximum transmitted power. . A 500 W carrier is to be modulated to 90% level. Determine the total transmitted power. 4. An AM broadcast station operates at its maximum allowed total output power of 50 kW and at 95% modulation. How much of its transmitted power (sidebands)? 5. The antenna current of an AM transmitter is 12 A when unmodulated but increases to 13 A when modulated. Calculate the percent modulation. 6. An intelligence signal is amplified by a 70% efficient amplifier before being combined with a 10 kW carrier to generate the AM signal.

If it is desired to operste at 100% modulation, what is the input power to the final intelligence amplifier? 7. A transmitter with a 10 kW carrier transmits 11. 2 kW when modulated with a single sine wave. Calculate the modulation index. If the carrier is simultaneously modulated with another sine wave at 50% modulation , calculate the transmitted power. 8. An AM transmitter at 27 MHz develops 10W of carrier power into a 50 ohm load. It is modulated by a 2 KHz sine wave between 20 and 90% modulation. Determine a. Component frequencies in the AM signal b.

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Maximum and minimum waveform voltage of the AM signal at 20% and 90% modulation. c. Sideband signal voltage and power at 20% and 90% modulation d. Load current at 20% and 90% modulation 9. An AM transmitter has 1 kW carrier and is modulated by three different sinewaves having equal amplitudes. If meff = 0. 8, calculate the individual values of m and the total transmitted power. 10. Given that the amplitude of an AM waveform can be expressed as the sum of the carrier peak amplitude and intelligence signal, derive the expression for an AM signal that shows the existence of carrier and side frequencies. 1. Determine the bandwidth required to transmit an FM signal with f1 = 10 kHz and a maximum deviation of ? = 20kHz. 12. An FM signal 2000 sin (2? x 108t + 2 sin ? x 104t), is applied to a 50 ohm antenna . Determine a. The carrier frequency b. The transmitted power c. mf d. fm e. BW 13. (a. ) Determine the permissible range in maximum modulation index for the commercial FM that has 30 Hz to 15 kHz modulating frequencies. (b. ) Repeat for a narrow band system that allows a maximum deviation of 10 kHz and 100 Hz to 3 kHz modulating frequencies. 14.

Explain what happens to the carrier in FM as mf goes from 0 up to 15. 15. Does the maximum deviation directly determine the bandwidth of an FM system? Explain the relationship between the bandwidth and deviation. 16. Calculate the bandwidth of an FM system when the maximum frequency deviation is 15 kHz and the modulating frequency is 3 kHz. Repeat for the modulating frequency 2. 5 kHz and 5 kHz. 17. What is the frequency swing of an FM broadcast transmitter when modulated 60%? 18. An FM broadcast transmitter is modulated 40% by a 5 KHz test tone.

When the percentage of modulation is doubled, what is the frequency swing of the transmitter? 19. An FM broadcast transmitter is modulated 50% by 7 kHz test tone. When the frequency of the test tone is changed to 5 kHz and the percentage of modulation is unchanged, what is the frequency swing of the transmitter? 20. An FM transmitter delivers , to 75 ohm antenna, a signal of v = 1000 sin (109t + 4 sin 104t). Calculate the carrier and modulating frequency, power, modulation index, deviation and bandwith.


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