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.
| 251. |
The angle modulated signal is given by |
| A. | 750 |
| B. | 7500 |
| C. | 75000 |
| D. | 75 |
| Answer» C. 75000 | |
| 252. |
Multiplying circuit used in FM transmitter |
| A. | Increases carrier frequency and decreases frequency deviation. |
| B. | Increases frequency deviation and decreases carrier frequency. |
| C. | Increases both carrier frequency and frequency deviation. |
| D. | Decreases both carrier frequency and frequency deviation. |
| Answer» D. Decreases both carrier frequency and frequency deviation. | |
| 253. |
A carrier A cos ct is modulated by a signal f(t) = 2 cos 10 |
| A. | 170 kHz |
| B. | 190 kHz |
| C. | 210 kHz |
| D. | 150 kHz |
| Answer» C. 210 kHz | |
| 254. |
Armstrong FM transmitter performs frequency multiplication in stages |
| A. | to increase the overall S/N ratio |
| B. | to reduce bandwidth |
| C. | to find the desired value of carrier frequency as well as frequency deviation |
| D. | for convenience |
| Answer» D. for convenience | |
| 255. |
The input to a linear delta modulator having a step-size = 0.62V is a sine wave with frequency f m and peak amplitude Em. If sampling frequency is f s = 40 kHz the combination of the sine wave frequency and the peak amplitude, where slope overload will take place is Em fm |
| A. | 0.3 V 8 kHz |
| B. | 1.5 V 4 kHz |
| C. | 1.5 V 2 kHz |
| D. | 3.0 V 1 kHz |
| Answer» C. 1.5 V 2 kHz | |
| 256. |
A linear delta modulator is designed to operate on speech signals limited to 3.4 kHz. The sampling rate is 10 time the Nyquist rate of the speech signal. The step size = 0 62 is 100 mV. The modulator is tested with a 1 kHz sinusoidal signal. The maximum amplitude of this test signal required to avoid slope overload is |
| A. | 2.04 V |
| B. | 1.08 V |
| C. | 4.08 V |
| D. | 2.16 V |
| Answer» C. 4.08 V | |
| 257. |
A PCM system uses a uniform quantizer followed by a 8- bit encoder. The bit rate of the system is equal to 10 |
| A. | 25 MHz |
| B. | 6.25MHz |
| C. | 12.5 MHz |
| D. | 50 MHz |
| Answer» C. 12.5 MHz | |
| 258. |
Following is not advantage of FM over AM |
| A. | noise immunity |
| B. | fidelity |
| C. | capture effect |
| D. | spluttering effect |
| Answer» E. | |
| 259. |
Which one is an advantage of AM over FM? |
| A. | FM is more immune to noise |
| B. | FM has better fidelity |
| C. | In a given frequency space, FM accommodates less number of channels as compared to AM |
| D. | FM has wide bandwidth |
| Answer» D. FM has wide bandwidth | |
| 260. |
Frequency deviation of AM signal |
| A. | 0.11 MHz |
| B. | 0.22 MHz |
| C. | 11 kHz |
| D. | 22 kHz |
| Answer» B. 0.22 MHz | |
| 261. |
Carrier frequency |
| A. | 53.6035 MHz |
| B. | 107.207 MHz |
| C. | 5360 kHz |
| D. | 1072 kHz |
| Answer» C. 5360 kHz | |
| 262. |
The carrier swing |
| A. | 0.22 MHz |
| B. | 0.11 MHz |
| C. | 22 kHz |
| D. | 11 kHz |
| Answer» B. 0.11 MHz | |
| 263. |
For the data given Q. 52 what will be the new bandwidth, if modulating signal amplitude is doubled? |
| A. | 170 kHz |
| B. | 190 kHz |
| C. | 320 kHz |
| D. | 340 kHz |
| Answer» D. 340 kHz | |
| 264. |
For the data given in Q. 52 what will be the new bandwidth, if modulating frequency is doubled? |
| A. | 170 kHz |
| B. | 190 kHz |
| C. | 180 kHz |
| D. | None of these |
| Answer» C. 180 kHz | |
| 265. |
Modulation index of FM signal |
| A. | 2.75 |
| B. | 13.75 |
| C. | 275 |
| D. | 27.5 |
| Answer» E. | |
| 266. |
In a single-tone FM discriminator (S |
| A. | proportional to deviation |
| B. | proportional to cube of deviation |
| C. | inversely proportional to deviation |
| D. | proportional to square of deviation |
| Answer» E. | |
| 267. |
A television signal is sampled at a rate of 25% above the Nyquist rate. The signal has a bandwidth of 6 MHz. The samples are quantized into 512 levels. The minimum bandwidth required to transmit this signal would be |
| A. | 135M bits/sec |
| B. | 67.5 M bits/sec |
| C. | 270 M bits/sec |
| D. | None of these. |
| Answer» B. 67.5 M bits/sec | |
| 268. |
The maximum deviation allowed in an FM broadcast system is 75 kHz. If the modulating signal is a single-tone sinusoid of 10 kHz, then the bandwidth of the FM signal |
| A. | 170 kHz |
| B. | 190 kHz |
| C. | 150 kHz |
| D. | None of these |
| Answer» B. 190 kHz | |
| 269. |
In ASK, the transmission bandwidth is equal to |
| A. | Baseband bandwidth |
| B. | Twice baseband bandwidth |
| C. | Four times baseband bandwidth |
| D. | None of these |
| Answer» C. Four times baseband bandwidth | |
| 270. |
The threshold in FM depends on |
| A. | Frequency deviation |
| B. | Power level of frequencies radiated at the receiver |
| C. | Both (A) and (B) |
| D. | None of these |
| Answer» D. None of these | |
| 271. |
A carrier is simultaneously modulated by two sine waves with modulation indices of 0.3 and 0.4, the total modulation index |
| A. | is 1 |
| B. | cannot be calculated unless the phase relations are known |
| C. | is 0.5 |
| D. | is 0.7 |
| Answer» D. is 0.7 | |
| 272. |
A non-linear device with a transfer characteristic given by i = (0 + 2V |
| A. | 18% |
| B. | 10% |
| C. | 20% |
| D. | 33.33% |
| Answer» C. 20% | |
| 273. |
A narrowband FM does not have the following feature |
| A. | it has two sidebands |
| B. | both sidebands are equal in amplitude |
| C. | both sidebands have same phase difference with respect to carrier |
| D. | it does not show amplitude variations |
| Answer» D. it does not show amplitude variations | |
| 274. |
A diode detector has a load of 1k shunted by a 10000 pF capacitor. The diode has a forward resistance of 1 . The maximum permissible depth of modulation, so as to avoid diagonal clipping, with modulating signal frequency of 10kHz will be |
| A. | 0.847 |
| B. | 0.628 |
| C. | 0.734 |
| D. | None of these |
| Answer» B. 0.628 | |
| 275. |
The threshold effect can occur in the system (i) FM (ii) AM (iii) AM with synchronous detection |
| A. | (i) only |
| B. | (ii) only |
| C. | (iii) only |
| D. | Both (i) and (iii) |
| Answer» D. Both (i) and (iii) | |
| 276. |
Which of the following process is a linear modulation process? |
| A. | NBFM |
| B. | WBFM |
| C. | NBPM |
| D. | None |
| Answer» D. None | |
| 277. |
If the carrier of a 100 per cent modulated AM wave is suppressed, the percentage power saving will be |
| A. | 50 |
| B. | 150 |
| C. | 100 |
| D. | 66.66 |
| Answer» E. | |
| 278. |
The message signal contain three frequencies 5 kHz, 10 kHz, 20 kHz respectively. The bandwidth of the AM signal is |
| A. | 40kHz |
| B. | 10 kHz |
| C. | 20 kHz |
| D. | 30 kHz |
| Answer» B. 10 kHz | |
| 279. |
A superheterodyne receiver is to operate in the frequency range of 550 kHz-1650 kHz with the intermediate frequency of 450 kHz. The receiver is tuned to 700. The capacitance ratio R = C |
| A. | 4.41 |
| B. | 2.1 |
| C. | 3 |
| D. | 9 |
| Answer» B. 2.1 | |
| 280. |
Assuming other parameters unchanged if the modulating frequency is halved in a modulating systems, the modulation index is doubled. The modulation system is |
| A. | A M |
| B. | FM |
| C. | Phase modulation |
| D. | Angle modulation |
| Answer» C. Phase modulation | |
| 281. |
An AM modulation has output x |
| A. | 14.14, 16.33 |
| B. | 50, 10 |
| C. | 22.36,13.46 |
| D. | None of these |
| Answer» B. 50, 10 | |
| 282. |
An AM modulator has output x |
| A. | 0.01 |
| B. | 0.02 |
| C. | 0.03 |
| D. | 0.04 |
| Answer» C. 0.03 | |
| 283. |
The double-sided spectrum of x |
| A. | A |
| B. | B |
| C. | C |
| D. | None of the above |
| Answer» C. C | |
| 284. |
The power in normalized message signal m |
| A. | 0.693 |
| B. | 0.542 |
| C. | 0.254 |
| D. | None of these |
| Answer» D. None of these | |
| 285. |
In NBFM, the maximum modulation frequency is 3 kHz and maximum deviation is 5 kHz. The modulation index is |
| A. | less than 1 |
| B. | equal to 1 |
| C. | greater than 1 |
| D. | None of these |
| Answer» D. None of these | |
| 286. |
FM broadcast band lies in |
| A. | VHF band |
| B. | UHF band |
| C. | SHF band |
| D. | None of these |
| Answer» B. UHF band | |
| 287. |
An increase in the modulation index leads increase in bandwidth in case of |
| A. | AM |
| B. | FM |
| C. | PM |
| D. | None |
| Answer» C. PM | |
| 288. |
FSK is preferred to ASK in applications where |
| A. | Fading of signal is prevalent |
| B. | Synchronous detection is not feasible |
| C. | Both of these |
| D. | None of these |
| Answer» D. None of these | |
| 289. |
The disadvantage of coherent FSK detection is that |
| A. | it leads to high signal fading |
| B. | it requires two synchronized oscillations |
| C. | Both of these |
| D. | None of these |
| Answer» C. Both of these | |
| 290. |
In FSK, the threshold level is independent of |
| A. | Carrier amplitude |
| B. | Carrier frequency |
| C. | Both of these |
| D. | None of these |
| Answer» B. Carrier frequency | |
| 291. |
Find the image rejection in a superheterodyne receiver with fIF = 455 kHz when tuned to MHz signal. Given Q. of the preselector and RF amplifier tuned circuit each is 65 |
| A. | 3.9 |
| B. | 2.9 |
| C. | 4.9 |
| D. | None of these |
| Answer» B. 2.9 | |
| 292. |
The disadvantage of FSK is that |
| A. | It does not provide sufficient S/N ratio |
| B. | It does not have low error probability |
| C. | It is not sufficient in its use of spectrum space |
| D. | None of these |
| Answer» D. None of these | |
| 293. |
One of the following cannot be used to remove the unwanted sideband in SSB. This is the |
| A. | filter system |
| B. | phase-shift method |
| C. | balanced modulator |
| D. | None of these |
| Answer» D. None of these | |
| 294. |
To provide two or more voice circuit with the same carrier, it is necessary to use |
| A. | ISB (Independent sideband) |
| B. | Carrier re-insertion |
| C. | SSB with pilot carrier |
| D. | None of these |
| Answer» B. Carrier re-insertion | |
| 295. |
In 50% modulated signal, the carrier is suppressed for transmission. The saving in transmitted power would be |
| A. | 88.9% |
| B. | 11.1% |
| C. | 72% |
| D. | 18% |
| Answer» B. 11.1% | |
| 296. |
Some properties are given below: |
| A. | (i) and (iv) only. |
| B. | (i) and (iii) only. |
| C. | (i), (ii) and (iii) only. |
| D. | All of these |
| Answer» E. | |
| 297. |
Application of Hilbert transform are: |
| A. | (i) and (ii) |
| B. | (i) and (iii) |
| C. | (ii) and (iii) |
| D. | (i), (ii) and (iii) |
| Answer» E. | |
| 298. |
Signal x(t) = 5 (1 + 2 cos 2000 t) can be recovered by |
| A. | (i) and (ii) only. |
| B. | (i) and (iii) only. |
| C. | (ii) and (iii) only. |
| D. | All. |
| Answer» D. All. | |
| 299. |
A DSB-SC wave is generated with f |
| A. | 1 MHz |
| B. | 0 33 MHz |
| C. | 0 5 MHz |
| D. | 3 MHz |
| Answer» D. 3 MHz | |