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The correct answer is (c) 0.0195W

To EXPLAIN: ELECTRICAL power is the rate at which electrical energy is converted to another FORM, such as MOTION, heat, or an electromagnetic field.

Power, P = 15 x 1300 x 10^-6 = 0.0195W.

Correct answer is (a) combination of DISC and cone

Explanation: Discone ANTENNA is a combination of disc and cone. A discone antenna is a version of a biconical antenna in which ONE of the cones is REPLACED by a disc. It is usually mounted vertically, with the disc at the TOP and the cone beneath. It is usually vertically mounted, with disc at top and the cone beneath.

Right OPTION is (a) 8μV

The EXPLANATION is: Thermal noise is DISTINCT from shotnoise, which CONSISTS of ADDITIONAL current fluctuations that occur when a voltage is applied and a macroscopic current starts to flow.

Right choice is (a) True

Easiest EXPLANATION: A MODEM (modulator-demodulator) is used to modulate one or more message signals USING one or more carrier WAVES on the transmitting side. It also demodulates the RECEIVED encoded signal to get the original information signal.

Right CHOICE is (a) True

To ELABORATE: HILBERT Transform of any signal produces a signal which has same amplitude as that of the original signal but suffers a phase-shift of -90 DEGREE. Consider f(t) be any signal and fh(t) is it’s Hilbert transform.

If we integrate both of them under proper boundary conditions, we get 0 which shows that both are mutually PERPENDICULAR i.e.

The correct choice is (d) helps to suppress the audio OUTPUT in the ABSENCE of sufficiently strong desired signal

The explanation is: A SQUELCH is a circuit which is a mean to impede, but not destroy a signal. It circuit blocks the output in the absence of sufficiently strong desired signal. It is widely used in two-way RADIOS to suppress the annoying sounds.

Correct choice is (d) super heterodyne receivers

The best explanation: SUPERHETERODYNE Receivers are radio receivers that use frequency mixing to convert a received high frequency signal to a fixed lower intermediate frequency which can be PROCESSED more conveniently. It is ALSO the most used receivers. It is used in a variety of applications from broadcast receivers to two-way radio COMMUNICATION links as WELL as many mobile radio communications systems.

Correct answer is (C) 62.5 X 10^-3

Easy EXPLANATION: STEP size is the voltage difference between one digital level (i.e. 0001) and the next one (i.e. 0010 or 0000). Quantization step size is the smallest possible difference in amplitude.

Therefore,

Step size,

The correct OPTION is (B) 3.25 x 10^-4

Best explanation: Quantization noise is a model of quantization ERROR introduced by quantization in the ANALOG-to-digital conversion (ADC) in telecommunication systems and signal processing. It is a rounding error between the analog input voltage to the ADC and the OUTPUT digitized value.

Therefore,

Right ANSWER is (C) 4 : 3

For EXPLANATION: Aspect ratio is an image projection attribute that describes the PROPORTIONAL relationship between the width of an image and its HEIGHT. The most common video-graphic aspect ratio is 4:3.

The correct OPTION is (a) It has LESSER bandwidth

Explanation: In SSB-SC(Single Side Band Suppressed CARRIER), the carrier is suppressed and either of the UPPER side-band and lower-sideband, are transmitted. This reduces it’s bandwidth to the frequency of the message signal.

Correct answer is (a) 50 dB

For explanation: SIGNAL to Noise ratio compares signal power to noise power. It determines how much signal is PRESENT in a transmitted wave compared to PRESENCE of noise. It is generally expressed in decibels(dB). For a hi-fi SYSTEM, it should be EQUAL to 50dB.

Correct option is (d) 25 TIMES each but alternately

Easiest explanation: In TELEVISION system in INDIA, each of odd and even fields are scanned 25 times but alternately.

The correct answer is (a) True

The best I can explain: HILBERT transform of a signal results in a signal with same amplitude but a phase SHIFT of -90 degrees. Thus, a signal and it’s Hilbert transform have same amplitude SPECTRUM i.e. they have same energy density spectrum and also correlation spectrum.

The CORRECT answer is (d) infinite

To elaborate: Frequency of DC signals is zero. For zero frequency, CAPACITIVE reactance XC is infinite as XC = 1/(f*C), where f is the frequency and C is the capacitance.

Correct choice is (B) 3mf

Explanation: A frequency TRIPLER is a frequency multiplier in which an electronic circuitgenerates an output signal WHOSE output frequency is a harmonic (multiple) of its input frequency. When a FM signal is passed through a frequency tripler, it INCREASES its modulation index 3 times. So the modulation index of output is 3mf.

Correct answer is (b) degrees

To explain: ANGULAR separation between the two half-power (-3DB) POINTS is KNOWN as beam width. It is usually EXPRESSED in degrees.

The correct ANSWER is (a) Slope Overload and Granular noise

The explanation is: DELTA modulation is an analog-to-digital and digital-to-analog signal conversion technique used for transmission of voice information where quality is not of primary importance. It is the simplest form of differential pulse-code modulation (DPCM) where the difference between SUCCESSIVE samples are ENCODED into n-bit data streams. The two major drawbacks in delta modulation are slope overload and granular noise. When step size becomes too small to track the original waveform it generates an error known as slope overload and granularity occurs when step size is too large.

The correct answer is (a) Open or Short Circuit

To EXPLAIN: Standing Wave Ratio (SWR) is defined as the ratio of the maximum radio-frequency (RF) voltage to the MINIMUM RF voltage along the line. If the line is open or short circuited, SWR is always 1.

The CORRECT choice is (c) 1.5Hz and 207Hz

For explanation: Comparing with the GENERAL FM EQUATION,

FM(t) = Ac sin(2πfct + βsin(2πfmt)),

Therefore,

Signal and Carrier frequency are RESPECTIVELY

The CORRECT CHOICE is (C) 700

Explanation: Q FACTOR = Frequency/Bandwidth

= 7MHz/10KHz = 700.

Right option is (B) Smith chart

To explain: Smith chart is highly used in RADIO frequency engineering. Because it is highly USEFUL in solving problems related with TRANSMISSION lines and matching circuits. It is highly useful for DISPLAYING multiple parameters like impedance, admittance etc simultaneously.

The CORRECT answer is (a) TRUE

Easiest EXPLANATION: The above STATEMENT is true because power density is EQUAL to

where,

Power Density = 1 mW

Pt = Power captured by antenna,

Area of antenna = 4πR^2 = 1m^2.

Correct answer is (a) True

For explanation I would say: ELECTROMAGNETIC radiation can travel through many forms of medium. They travel at the speed of light in air or free space, which are ideal MEDIA. However conductive media like metals form a barrier through which they do not travel. There are also some media through which when they travel, GET attenuated. EM waves are attenuated as they travel because both field and power DECREASE as distance increases.

The correct choice is (d) Pt×Gt

The explanation: Effective RADIATED Power (ERP) measures the combination of the power emitted by the transmitter and the ability of the antenna to DIRECT that power in a GIVEN direction. Thus, Effective Radiated Power is equal to the PRODUCT of antenna GAIN (Gt) and power transmitted (Pt).

Right option is (a) \(\frac{P_t}{4 \pi R^2}\)

For EXPLANATION: POWER of a transmitter that is radiated from an isotropic antenna will have a uniform power density in all direction. An isotropic antenna is an ideal antenna that radiates its power UNIFORMLY in all directions. There is no actual physical isotropic antenna. However, an isotropic antenna is often used as a reference antenna for the antenna gain. The power density at any distance ‘R’ for an isotropic antenna is EQUAL to \(\frac{P_t}{4 \pi R^2}\).

The correct CHOICE is (a) OPTICAL recording

For explanation I WOULD say: Compact DISK (CD) is mainly used for storage of DATA. It was developed only for store and play only audio but was later adapted for storage of data also. It mainly used optical recording and retrieval.

Correct option is (a) True

To ELABORATE: It is due to the R^2 term in formula, . Thus, the RECEIVED signal power is inversely PROPORTIONAL to the distance between antenna and SOURCE.

Right OPTION is (a) True

Explanation: IF amplifiers are used to change the frequency levels in CIRCUITS that are too SELECTIVE, difficult to tune, and unstable. However, VIDEO amplifier is used to amplify video signals before passing them to a Cathode ray tube. And there is no need of IF amplifier stages for a video monitor.

Right choice is (a) True

The BEST I can explain: A helical ANTENNA is an antenna consisting of one or more conducting wires (monofilar, bifilar, or quadrifilar with 1, 2, or 4 wires respectively) wound in the form of a helix. In helical antenna, polarization is equally divided between vertical and horizontal components and thus it is circularly POLARIZED.

Correct option is (c) 700KHz

To elaborate: The image FREQUENCY is an undesired input frequency which is demodulated by superheterodyne RECEIVERS along with the desired incoming signal. This results in two stations being received at the same time, thus producing interference. In the GIVEN problem, Image frequency is equal to (1200 – 500) which is equal to 700KHz.

Correct choice is (a) True

To explain: A discone antenna is a version of a biconical antenna in which one of the cones is REPLACED by a disc. It is usually mounted vertically, with the disc at the TOP and the cone beneath. Discone antenna is a combination of disc and cone. Discone antenna is omnidirectional so it is mainly used in UHF range. It is especially used in airports.

Correct answer is (a) after detector

For explanation I would say: Squelch is a circuit that acts to SUPPRESS the audio (or video) OUTPUT of a receiver in the absence of a SUFFICIENTLY strong desired INPUT signal. Squelch is added to suppress NOISE. It is added after detector when there is no carrier.

Correct answer is (B) 42mV/m

Best EXPLANATION: SINCE, Field strength (E) is directly PROPORTIONAL to the square root of transmission power i.e. E ∝ √Pt. Thereforewhich gives x = 42mV/m

Right answer is (b) False

To explain: Field Strength is the intensity of an electric or MAGNETIC field. ACTUALLY the Field strength (E) is directly proportional to the square root of transmission POWER i.e. E ∝ √Pt.

Correct option is (b) False

To elaborate: The infrared (IR) and the ultraviolet(UV) rays represent the two extremities of the visible spectrum (400-700nm). While IR represents electromagnetic RADIATION with WAVELENGTHS longer than those of visible light, UV represents wavelengths shorter than visible light. Each time we press any button of TV REMOTE, it sends a beam of infrared rays. For different commands, it sends out different BEAMS that are detected by a microchip lying INSIDE TV.

Correct CHOICE is (a) it is INVERSELY proportional to thickness

Best explanation: The thickness of capacitor affects the VALUE of capacitance because capacitance is dependent on structure and distance between TWO plates.

Thus, Capacitance, C = ^A×∈⁄t so it is inversely proportional to thickness.

The correct answer is (d) channel

Easy explanation: Channel acts as a path for taking SIGNALS to the receiver. It is a medium of transmission of data from SOURCE to DESTINATION. There is a high PROBABILITY of involving noise at the channel.