MCQOPTIONS
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MCQOPTIONS
This section includes 299 Mcqs, each offering curated multiple-choice questions to sharpen your Communication knowledge and support exam preparation. Choose a topic below to get started.
| 201. |
An angle-modulated signal is given by |
| A. | 10.5 kHz, 140 rad |
| B. | 6 kHz, 80 rad |
| C. | 10.5 kHz, 100 rad |
| D. | 7.5 kHz,100 rad |
| Answer» E. | |
| 202. |
For a bit-rate of 8 kbps the best possible values of the transmitted frequencies in a coherent binary FSK system are |
| A. | 16 kHz and 20 kHz |
| B. | 20 kHz and 32 kHz |
| C. | 20 kHz and 40 kHz |
| D. | 32 kHz and 40 kHz |
| Answer» E. | |
| 203. |
A 1 MHz sinusoidal carrier is amplitude modulated by a symmetrical square wave of period 100 sec. Which of the following frequencies will not be present in the modulated signal? |
| A. | 990 kHz |
| B. | 1010 kHz |
| C. | 1020 kHz |
| D. | 1030 kHz |
| Answer» D. 1030 kHz | |
| 204. |
10 signals, each band-limited to 5 kHz are to be transmitted over a single channel by frequency division multiplexing. If AM-SSB modulation guard band of 1kHz is used then the bandwidth of the multiplexed signal will be |
| A. | 79 kHz |
| B. | 60 kHz |
| C. | 59 kHz |
| D. | 61 kHz |
| Answer» D. 61 kHz | |
| 205. |
In the circuit shown below between the terminal A and B an a.c. voltage source of frequency 400 Hz is connected. Another a.c. voltage of 1.0 MHz is connected between C and D. The output between E and F contains components at |
| A. | 400 Hz, 1MHz, 1000 4 kHz, 999 6 kHz |
| B. | 1 MHz, 1000 4 kHz, 999 6 kHz |
| C. | 400 Hz, 1000 4 kHz, 999 6 kHz |
| D. | 1000 4 kHz, 999 6 kHz |
| Answer» E. | |
| 206. |
In an AM signal the received signal power is 10 10 W with a maximum modulation signal of 5 kHz. The noise spectral density at the receiver input is 10 |
| A. | 43 dB |
| B. | 66 dB |
| C. | 56 dB |
| D. | 33 dB |
| Answer» B. 66 dB | |
| 207. |
The AM signal that occupies the greatest bandwidth is for the same amplitude |
| A. | 5 kHz Square wave |
| B. | 5 kHz Sine wave |
| C. | 5 kHz Triangular wave |
| D. | 5 kHz Saw tooth wave |
| Answer» B. 5 kHz Sine wave | |
| 208. |
Suppose we wish to transmit the signal x(t) = sin 200 t + 2 sin 400 t using a modulation that create the signal g(t) = x (t) sin 400 t. If the product g(t) sin 400 t is passed through an ideal LPF with cut-off frequency 400 and pass band gain of 2, the signal obtained at the output of the LPF is |
| A. | sin 200 t |
| B. | 1 2 sin 200 t |
| C. | 2 sin 200 t |
| D. | 0 |
| Answer» B. 1 2 sin 200 t | |
| 209. |
Let x(t) be a signal band-limited to 1 kHz. Amplitude modulation is performed to produce signal g(t) = x(t) sin 2000 t. A proposed demodulation technique is illustrated in fig. below. The ideal low pass filter has cut-off frequency 1 kHz and pass band gain 2. The y(t) would be |
| A. | 2 y(t) |
| B. | y(t) |
| C. | y(t) 2 |
| D. | 0 |
| Answer» E. | |
| 210. |
In an AM wave, the total power content is 600 W and that of each sideband is 75 W. The modulation index is |
| A. | 53.3% |
| B. | 60.7% |
| C. | 81.6% |
| D. | 40.3% |
| Answer» D. 40.3% | |
| 211. |
In figure given below |
| A. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>sin 2 t</center></td></tr><tr><td style="text-align: center;">2t</td></tr></table> |
| B. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>sin 2 t</center></td><td rowspan="2"> &plus;</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>sin t</center></td><td rowspan="2">cos 3 t</td></tr><tr><td style="text-align: center;">2t</td><td style="text-align: center;">t</td></tr></table> |
| C. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>sin 2 t</center></td><td rowspan="2"> &plus;</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>sin 0.5 t</center></td><td rowspan="2">cos 1.5 t</td></tr><tr><td style="text-align: center;">2t</td><td style="text-align: center;">t</td></tr></table> |
| D. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>sin 2 t</center></td><td rowspan="2"> &plus;</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>sin t</center></td><td rowspan="2">cos 0.75 t</td></tr><tr><td style="text-align: center;">2t</td><td style="text-align: center;">t</td></tr></table> |
| Answer» D. <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>sin 2 t</center></td><td rowspan="2"> &plus;</td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>sin t</center></td><td rowspan="2">cos 0.75 t</td></tr><tr><td style="text-align: center;">2t</td><td style="text-align: center;">t</td></tr></table> | |
| 212. |
Consider a system shown below. Let X(f) and Y(f) denotes the Fourier transform of x(t) and y(t) respectively. The positive frequencies where Y (f) has spectral peak are |
| A. | 1 kHz and 24 kHz |
| B. | 2 kHz and 24 kHz |
| C. | 1 kHz and 14 kHz |
| D. | 2 kHz and 14 kHz |
| Answer» C. 1 kHz and 14 kHz | |
| 213. |
A signal m(t) band-limited to 3 kHz is sampled at a rate |
| A. | 1536 kHz |
| B. | 768 kHz |
| C. | 472 kHz |
| D. | 1344 kHz |
| Answer» C. 472 kHz | |
| 214. |
An AM wave is given by |
| A. | 0.4 |
| B. | 0.5 |
| C. | 0.3 |
| D. | 0.9 |
| Answer» C. 0.3 | |
| 215. |
The most suitable method for detecting a modulated signal (2 5 + 5 cos |
| A. | envelope circuit |
| B. | synchronous detector |
| C. | ratio detector |
| D. | Both (A) and (B) |
| Answer» C. ratio detector | |
| 216. |
The allocation of power in each sidebands if percentage of modulation is changed to 80% |
| A. | 320W |
| B. | 160W |
| C. | 640W |
| D. | 180W |
| Answer» C. 640W | |
| 217. |
What is the percentage modulation? |
| A. | 80% |
| B. | 40% |
| C. | 100% |
| D. | 89.4% |
| Answer» E. | |
| 218. |
A carrier is amplitude modulated by two sinusoidal signals of different frequencies with individual modulation depths of 0.3 and 0.4. The sideband power is |
| A. | 12% |
| B. | 9% |
| C. | 11.1% |
| D. | 10% |
| Answer» D. 10% | |
| 219. |
For AM modulated signal given by i = 10 + K |
| A. | 0.5 |
| B. | 0.2 |
| C. | 1 |
| D. | 0.4 |
| Answer» C. 1 | |
| 220. |
The percentage increase in signal power of a carrier amplitude modulated 100% by a square wave |
| A. | 50% |
| B. | 100% |
| C. | 200% |
| D. | None of these |
| Answer» C. 200% | |
| 221. |
The d.c. power to a modulated class C amplifier is 500 W. The power that modulator must supply for 100% modulation applied at the output electrode |
| A. | 500 W |
| B. | 250 W |
| C. | 1000 W |
| D. | 2000 W |
| Answer» C. 1000 W | |
| 222. |
C (t) and m(t) are used to generate an AM signal. The = 0 5 of generated AM, then the quantity |
| A. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">2</td></tr></table> |
| B. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">4</td></tr></table> |
| C. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">3</td></tr></table> |
| D. | <table><tr><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>1</center></td></tr><tr><td style="text-align: center;">8</td></tr></table> |
| Answer» E. | |
| 223. |
An AM transmitter is coupled to an aerial. The input current is observed to be 5 A. With modulation the current value increases to 5.9 A. The depth of modulation is |
| A. | 83.4% |
| B. | 88.6% |
| C. | 78.2% |
| D. | 74.3% |
| Answer» C. 78.2% | |
| 224. |
A 2 MHz carrier is amplitude modulated by a 500 Hz modulation signal to a depth of 60%. If the unmodulated carrier power is 1kW, the power of the modulated signal is |
| A. | 1.83kW |
| B. | 1.36kW |
| C. | 1.18kW |
| D. | 1.26kW |
| Answer» D. 1.26kW | |
| 225. |
Indicate which one of the following advantage of the phase cancellation method of obtaining SSB over the filter method is false? |
| A. | Switching from one sideband to the other is simpler. |
| B. | It is possible to generate SSB at any frequency. |
| C. | SSB wilth lower audio frequency present can generated. |
| D. | There are more balanced modulators, therefore, the carrier is suppressed better. |
| Answer» E. | |
| 226. |
An AM broadcast station operates at its maximum allowed total of 100 kW with 90% modulation. The power in the intelligence part is |
| A. | 28.8 kW |
| B. | 71.2 kW |
| C. | 35.6 kW |
| D. | None of these |
| Answer» B. 71.2 kW | |
| 227. |
A 1 kW carrier is to be modulated to a 80% level. The total transmitted power would be |
| A. | 2 kW |
| B. | 1.32 kW |
| C. | 1.4 kW |
| D. | None of these |
| Answer» C. 1.4 kW | |
| 228. |
In an SSB transmitter, one is most likely to find a |
| A. | class C audio amplifier |
| B. | tuned modulator |
| C. | class B RF amplifier |
| D. | class A RF amplifier |
| Answer» D. class A RF amplifier | |
| 229. |
When the modulation index of a wave is doubled, the antenna current is also doubled. The AM system being used is |
| A. | Single-sideband, full carrier. |
| B. | Vestigial sideband. |
| C. | Single-sideband, suppressed carrier |
| D. | Double-sideband, full carrier |
| Answer» C. Single-sideband, suppressed carrier | |
| 230. |
Indicate the false statement regarding the advantages of SSB over double sideband, full-carrier AM |
| A. | More channel space is available. |
| B. | Transmitter circuits must be stable, giving better reception. |
| C. | The signal is more noise-resistant. |
| D. | Much less power is required for the same signal strengths. |
| Answer» B. Transmitter circuits must be stable, giving better reception. | |
| 231. |
The positive RF peaks of an AM voltage rise to a maximum value of 12 V and drop to a minimum value of 4V. The modulation index assuming single tone modulation is |
| A. | 3 |
| B. | 1/3 |
| C. | 1/4 |
| D. | 1/2 |
| Answer» E. | |
| 232. |
The total transmitted power given by the AM signal |
| A. | 57.25 W |
| B. | 62.25 W |
| C. | 56.25 W |
| D. | None of these |
| Answer» B. 62.25 W | |
| 233. |
The DSB-SC signal is detected by |
| A. | removing the carrier |
| B. | removing one sideband |
| C. | re-injecting the carrier |
| D. | None of these |
| Answer» D. None of these | |
| 234. |
The filter required to obtain SSB from DSB signal is |
| A. | LPF |
| B. | HPF |
| C. | BPF |
| D. | None |
| Answer» D. None | |
| 235. |
The advantage of SSB-SC system is that it provides |
| A. | Higher frequency of transmission |
| B. | Better quality of communication |
| C. | Simpler and inexpensive circuitry |
| D. | None of these |
| Answer» B. Better quality of communication | |
| 236. |
Which of the following techniques is acceptable for voice communication? |
| A. | DSB-SC |
| B. | SSB |
| C. | Both (A) and (B) |
| D. | None of these |
| Answer» C. Both (A) and (B) | |
| 237. |
Completely suppressed carrier transmission is |
| A. | cheaper in cost |
| B. | simpler in design |
| C. | never produced commercially |
| D. | None of these |
| Answer» D. None of these | |
| 238. |
Which of the following AM techniques provide the advantages of greater signal power and reduction of bandwidth? |
| A. | DSB-SC |
| B. | SSB |
| C. | USB |
| D. | None |
| Answer» C. USB | |
| 239. |
Vestigial sideband modulation is normally used for |
| A. | HF point-to-point communications |
| B. | manual broadcasting |
| C. | TV broadcasting |
| D. | stereo broadcasting |
| Answer» B. manual broadcasting | |
| 240. |
The SSB modulator is known as |
| A. | Balanced modulator |
| B. | Product modulator |
| C. | Amplitude modulator |
| D. | None of these |
| Answer» C. Amplitude modulator | |
| 241. |
In phase-shift SSB modulator, the input signals one of the balanced modulators are phase-shifted by |
| A. | 45 |
| B. | 90 |
| C. | 180 |
| D. | 30 |
| Answer» C. 180 | |
| 242. |
The VSB signal is produced form the DSB signal by employing |
| A. | Simpler filters |
| B. | Balanced modulator |
| C. | Ring modulator |
| D. | None of these |
| Answer» D. None of these | |
| 243. |
An FM signal for broadcast in the 88-108 MHz range, band has a frequency deviation of 15 kHz. Find the% modulation of this signal |
| A. | 40% |
| B. | 20% |
| C. | 66% |
| D. | 50% |
| Answer» C. 66% | |
| 244. |
The modulating frequency in frequency modulation is increased from 10 kHz to 20 kHz. The bandwidth is |
| A. | doubled |
| B. | halved |
| C. | increases by 20 kHz |
| D. | increased tremendously |
| Answer» D. increased tremendously | |
| 245. |
Which one of the following statement is correct? In a ratio detector: |
| A. | Linearity is worse than that of a phase discriminator |
| B. | Stabilization is provided, against signal strength variations. |
| C. | The output is twice of that obtainable from a similar phase discriminator. |
| D. | The circuit is same as that in a discriminator, except that the diode connections are reversed. |
| Answer» E. | |
| 246. |
An AM wave |
| A. | 0.17 ms |
| B. | 1.7 ms |
| C. | 0.212 ms |
| D. | None of these |
| Answer» D. None of these | |
| 247. |
A binary channel with capacity 30 k bits/sec is available for PCM voice transmission. If signal is band limited to 3 kHz then the appropriate values of quantizing level L and the sampling frequency will be |
| A. | 64, 6 kHz |
| B. | 32, 6 kHz |
| C. | 128, 6 kHz |
| D. | 32, 12 kHz |
| Answer» C. 128, 6 kHz | |
| 248. |
Which one of the following is represented by |
| A. | SSB upper sideband signal. |
| B. | DSB suppressed carrier signal. |
| C. | AM signal. |
| D. | Narrow band FM signal. |
| Answer» E. | |
| 249. |
Which of the following is the best transmission efficiency? |
| A. | SSB |
| B. | VSB |
| C. | FM |
| D. | PM |
| Answer» D. PM | |
| 250. |
In contrast to analog transmission, digital system can employ |
| A. | Regeneration |
| B. | Error control coding |
| C. | Both of these |
| D. | None of these |
| Answer» D. None of these | |