InterviewSolution
Saved Bookmarks
InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 201. |
A narrow band noise n() has symmetrical spectrum and has power density spectrum 0.2 x 10. The power density of quadrature component is |
| Answer» . | |
| 202. |
The radio receivers mostly used now a days are |
| Answer» Now-a-days only super heterodyne radio receivers are used. | |
| 203. |
The reactance of coupling capacitors, for DC quantities, is |
| Answer» For zero frequency capacitive reactance is infinite. | |
| 204. |
An AM wave is given by () = 20 (1 + 0.5 cos 10 + 0.3 cos 10 cos 10 ) the modulation index of the envelope is |
| Answer» . | |
| 205. |
The modulating frequency in frequency modulation is increased from 10 kHz to 30 kHz. The bandwidth is increased by |
| Answer» BW = 2fm(1 + β) for β >> 1 B.W. a 2fm . | |
| 206. |
In the television system in India, each frame is scanned |
| Answer» Each frame is divided into odd and even fields. Each field is scanned 25 times so that each frame is scanned 50 times. | |
| 207. |
Each kilometer of travel in electromagnetic radiation means a time delay of |
| Answer» Since velocity of em waves is 300 m/ms, each kilometer means time delay of 3.3 μs. | |
| 208. |
A video monitor is exactly similar to TV receiver. |
| Answer» Trinitron is a colour picture tube. | |
| 209. |
A RADAR can be used to |
| Answer» Radar is used for all the three purposes. | |
| 210. |
A remote control of TV uses a 10 bit word. The maximum number of total commands it can transmit is |
| Answer» 210 = 1024. | |
| 211. |
Telecine equipment in a TV studio consists of |
| Answer» It may be any one of these. | |
| 212. |
AM amplifier having noise figure of 20 dB and available power gain of 15 dB is followed by a mixer circuit having noise figure of 9 dB. The overall noise figure as referred to input in dB is |
| Answer» . | |
| 213. |
TV signal strength when expressed in dB m has the reference of |
| Answer» TV signal strength has a reference of . | |
| 214. |
The time required for horizontal blanking is 16% of that for each horizontal line. If horizontal time is 63.5 μs, the horizontal blanking time for each line is about |
| Answer» . | |
| 215. |
When the number of quantising levels is 16 in PCM, the number of pulses in a code group will be |
| Answer» 2n = L n = 4. | |
| 216. |
The video heads, in VCR, feed the other circuit |
| Answer» Rotatory transformer, in VCR, has one stationary and one rotating winding. | |
| 217. |
A high pulse repetition frequency in a radar |
| Answer» PRF does not have any effect on range of radar. | |
| 218. |
In PCM, the biggest disadvantage as compared to AM is |
| Answer» PCM requires large bandwidth. | |
| 219. |
In cellular telephone each cell is designed to handle |
| Answer» Each cell is designed for 45 two way conversations. | |
| 220. |
A UPS contains |
| Answer» Rectifier is needed to charge the battery. Inverter is needed to feed the loads during power failure. | |
| 221. |
A transmitter power of 10 W is increased by 30 dB. The effective radiated power is |
| Answer» or P = 10000 W. | |
| 222. |
It is desired to couple a coaxial line to a two parallel wire line. It is best to use |
| Answer» Balun gives 4 : 1 impedance transformation and is suited for coupling a coaxial line to two wire line. | |
| 223. |
24 telephone channels are frequency division multiplexed using an SSB modulation. Assuming 3 kHz per channel, the required band width is |
| Answer» Since SSB modulation is used, bandwidth = 24 x 3 = 72 kHz. | |
| 224. |
When the carrier is unmodulated, a certain transmitter radiates 9 kW when the carrier is sinusoidally modulated the transmitter radiates 10.125 kW. The modulation index will be |
| Answer» . | |
| 225. |
If a line is terminated in characteristic impedance Z, the input impedance measured at the input will be |
| Answer» If line is terminated in Z0, the input impedance is Z0. | |
| 226. |
In a TV, the output from RF tuner is about |
| Answer» It is about 1 mV. | |
| 227. |
24 telephone channels, each band limited to 3.4 kHz, are to be time division multiplexed by using PCM, calculate the bandwidth of PCM system for 128 quantization levels and an 8 KHz sampling frequency |
| Answer» Given, n = 24, fm = 3.4 kHz M = 128, 2N = 128 n = 7 But fs = 2fm, here we will consider fs (sampling) frequency instead at 2fm 2 x 3.4 kHz 6.8 KHz. B.W. = [24(7 + 1)] 8 kHz = 1.54 MHz. | |
| 228. |
At night the ionosphere can be considered to be consisting of |
| Answer» During night D layer is almost absent. Moreover F1 and F2 layers merge to form single F2 layer. Hence only D and F2 layers at night. | |
| 229. |
A balun transformer gives an impedance transformation of |
| Answer» Balun gives 4 : 1 impedance transformation and can be used to interconnect twin wire feeder cable to coaxial cable. | |
| 230. |
In an FM signal, the modulating frequency is 2 kHz and maximum deviation is 10 kHz. The bandwidth requirement is |
| Answer» Bandwidth = 2(10 + 5) j 30 kHz. This is an approximate value. Exact value is 32 kHz. | |
| 231. |
The effective length of antenna is different from actual length due to |
| Answer» The effective length is more than actual length due to the effect of top loading and end effects. | |
| 232. |
A 1000 kHz carrier wave modulated 40% at 40000 Hz is applied to a resonant circuit tuned to a carrier frequency and having Q = 140. What is the degree of modulator after transmission through the circuit? |
| Answer» m0 = m(1 + 4Q2δ2)1/2 . | |
| 233. |
The EHT voltage in a picture tube of TV is |
| Answer» EHT voltage is 1 kV for each diagonal inch of CRT screen. | |
| 234. |
In a TV receiver there is no raster, no picture and no sound. The most likely defective stage is |
| Answer» If power supply is working, raster will exist. | |
| 235. |
A 100 + 100 Ω load is to be matched to a line with Z = 300 Ω to give SWR = 1. The reactance of stub is |
| Answer» ZL = 100 + j 100 Susceptance of stub = j 0.005 mho. . | |
| 236. |
A message signal with bandwidth 10 kHz is lower sideband SSB modulated with carrier frequency = 10 Hz. The resulting signal is then passed though a narrow band frequency modulator with carrier frequency = 10 Hz. The bandwidth of the output would be |
| Answer» Bandwidth = 2Δf + 2B But for NBFM, B < 1 BW ≈ 2fm 2fc1 2 x 106 Hz. | |
| 237. |
In a PCM system, if the code word length is increased from 6 to 8 bits, the signal to quantization noise ratio improves by the factor. |
| Answer» Given n1 = 6, n2 = 8, then (SNR)Q = 22(n2 - n1) 16. | |
| 238. |
For 10 bit PCM system, the signal to quantization noise ratio is 62 dB. If the number of bits is increased by 2, then the signal to quantization noise ratio will |
| Answer» = (SNR)Q + 6.02 x 2 (SNE)Q + 12 dB. | |
| 239. |
A signal is sampled at 8 kHz and is quantized using 8 bit uniform quantizer. Assuming SNR for a sinusoidal signal, the correct statement for PCM signal with a bit rate of is |
| Answer» where n is no. of bit, fs is sampling frequency. SNR = 1.76 + 6.02n = 1.76 + 6.02 x 8 49.8 dB. | |
| 240. |
Generally a VCR has |
| Answer» VCR has two rotating leads about 180° apart. | |
| 241. |
An S/N ratio of 3 expressed in db is |
| Answer» 10 log10 3 = 4.8 . | |
| 242. |
In a 100% amplitude modulated signal, the power in the upper sideband when carrier power is to be 100 W and modulation system SSBSC, is |
| Answer» Modulation index = 100% 1 Pc = 100 W . | |
| 243. |
The simplest method of suppression of unwanted side band in AM is |
| Answer» Unwanted frequency is removed by filtering. | |
| 244. |
The material used for the magnet of moving coil cone type loudspeaker is |
| Answer» Alnico produces a strong magnetic field. | |
| 245. |
CCIR system B employs |
| Answer» 625 lines divided into odd and even fields, i.e., 2 : 1 interlace. | |
| 246. |
The power to the base unit of a cordless telephone is supplied by |
| Answer» Base unit is fed from ac mains and portable unit from battery. | |
| 247. |
For attenuation of low frequencies we should use |
| Answer» Series capacitance has high reactance for low frequencies. | |
| 248. |
A sinusoidal voltage amplitude modulates a carrier of peak value 5 kV. Each side band has an amplitude of 500 V. The modulation index is |
| Answer» . | |
| 249. |
Kell factor is about |
| Answer» Kell factor indicates reduction in vertical resolution and varies from 0.65 to 0.85. | |
| 250. |
If the oscillator output is modulated by audio frequencies upto 10 kHz, the frequency range occupied by the side bands will be |
| Answer» Sideband frequencies will be fc ± fm. | |