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The correct choice is (b) waveform for which frequency, amplitude or PHASE is varied

The explanation: A carrier wave is modulated in terms of amplitude, frequency or phase, with RESPECT to an input SIGNAL for CONVEYING information. Carrier wave has GENERALLY higher frequency than the input signal.

Right choice is (b) fundamental sine WAVE and ODD harmonics

The explanation: A square wave is a non-sinusoidal periodic waveform with STEADY frequency, in which the AMPLITUDE ALTERNATES between a fixed maximum and minimum value. According to Fourier analysis, an ideal square wave, with amplitude one, can be represented as an infinite sum of sinusoidal waves. An ideal square wave contains only components of odd integer harmonics.

The correct choice is (a) Luminance amplifier

To explain I would SAY: Luminance amplifier is mostly used by the Contrast Function, in TV sets. It helps to changes the contrast or picture quality of television with respect to the received VISUAL SIGNALS, by MAKING the contrast optimum.

Correct option is (a) frequency MODULATION

The explanation is: FSK (Frequency Shift Keying) is a method to transmit DIGITAL signals, which are in form of BINARY DATA. FSK i.e. Frequency Shift Keying involves frequency modulation that assigns bit values to discrete frequency while ASK assigns bit values to discrete AMPLITUDE.

The correct OPTION is (a) be doubled

To EXPLAIN I would SAY: Range of antenna is DIRECTLY proportional to antenna diameter. So if diameter of antenna is doubled its range ALSO doubled.

The correct answer is (d) 12.6 KHz

To ELABORATE: MODULATING FREQUENCY (fm) = Vmax-Vmin, where,

Vmax = Maximum Amplitude of an amplitude modulated,

Vmin = Minimum amplitudeof an amplitude modulated,

fm = 7KHZ – 700Hz = 6.3KHz

Bandwidth = 2fm = 2 X 6.3 = 12.6 KHz.

The correct CHOICE is (a) 158

To explain: The characteristic impedance or surge impedance (Z0) of a uniform TRANSMISSION line is the RATIO of the AMPLITUDES of voltage and current of a single wave propagating along the line; which is, a wave travelling in one direction in the absence of reflections in the other direction.

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Right choice is (a) 3

Easy explanation: The voltage standing wave ratio (VSWR) is defined as the ratio of the maximum to minimum voltage on a loss-less LINE. In this way, the VSWR is measured at a particular point and the voltage MAXIMA and MINIMA do not need to be determined along the length of the line.

The CORRECT answer is (a) 1000 KHz

Best EXPLANATION: Frequencies present in output are of the form FC ± fm, fc ± 2fm, fc ± 3fm. And 1000 KHz is a MULTIPLE of NONE in the range. Whereas, rest options are one of the multiples in the range.

Correct ANSWER is (B) 2 x 10^-4

Explanation: Duty cycle is the PROPORTION of TIME during which a component, device, or system is operated. The duty cycle can be expressed as a ratio or as a percentage.

The correct answer is (d) INFINITY

The explanation is: WDM (WAVE Division Multiplexing) is partly similar to FDM (Frequency Division Multiplexing). FDM is USED for signal TRANSMISSION through a twisted-pair cable while WDM is used to transmit signals through optical fiber cables. Frequency difference between WDM and FDM is infinity.

The correct option is (c) 5W

The best I can 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 = V x I. By SUBSTITUTING the values of voltage(V) and current(I), we have P = (5×10^3)(1000×10^-6) = 5W.

The correct answer is (a) Crystal

The explanation: Piezoelectric effect is the ability of MATERIALS to generate an electric CHARGE in response to applied mechanical stress. Crystals which DEMONSTRATE the piezoelectric effect produce voltages when they are deformed. The crystal microphone uses a thin strip of piezoelectric material attached to a diaphragm. The two SIDES of the crystal ACQUIRE opposite charges when the crystal is deflected by the diaphragm.

The correct choice is (a) TIME DIVISION MULTIPLEXING

For explanation I would say: TDM stands for Time Division Multiplexing. It is used to transmit and receive independent signals over a common signal PATH with the help of synchronized switches.

Right answer is (b) True

For explanation: Multiplexing is the method of COMBINING two or more than two signals into one, in such a WAY that each individual signal can be retrieved at the receiver. Both TDM and FDM are used to multiplex DIFFERENT signals into a single carrier. However, TDM is used to transmit and RECEIVE independent signals over a common signal path with the help of synchronized switches. WHEREAS, in case of FDM, the total bandwidth is divided into a series of non-overlapping frequency bands and each band is used to carry a separate signal.

The CORRECT option is (a) GIVES same AMOUNT of time to each device

For explanation: TDM is a method of putting multiple data streams in a single signal by separating the signal into many segments, each having a very short duration. Each individual data stream is reassembled at the receiving end based on the timing. Synchronous TDM gives EXACTLY the same amount of time to each connected device. It allocates time to every device EVEN if a device has nothing to transmit.

Right choice is (a) analog signals

The explanation: Frequency Division Multiplexing (FDM) is a networking TECHNIQUE in which MULTIPLE data signals are combined for simultaneous transmission VIA a shared communication medium. FDM uses a carrier SIGNAL at a discrete frequency for each data stream and then combines many modulated signals. FDM is used to multiplex multiple analog signals. FDM is APPLIED when the bandwidth of the link is greater than the combined bandwidth of signals to be transmitted.

Right choice is (a) True

The best explanation: Frequency Division Multiplexing (FDM) is a networking technique in which multiple data signals are COMBINED for SIMULTANEOUS transmission via a shared communication medium. FDM uses a carrier signal at a discrete frequency for each data stream and then combines many MODULATED signals. Orthogonal frequency division multiplexing is used to encode multiple carrier frequencies. It is mainly used for latest WIRELESS telecommunications.

Correct choice is (b) TDM

The best explanation: Time Division Multiplexing is used to transmit DIGITAL signals. FDM and WDM techniques are used to transfer analog signals. WDM (Wave Division Multiplexing) is PARTLY similar to FDM (Frequency Division Multiplexing). FDM is used for SIGNAL transmission through a twisted-pair CABLE while WDM is used to transmit signals through optical fiber cables.

Right CHOICE is (a) True

To elaborate: Both Frequency Division Multiplexing (FDM) and TIME Division Multiplexing (TDM) are based on orthogonal multiplexing.Orthogonal multiplexing is a method of encoding digital data on MULTIPLE carrier frequencies.

The CORRECT answer is (c) Synchronous TDM

The explanation is: TDM is a method of allowing multiple data streams in a single signal by separating the signal into many segments, each having a very short duration. Each INDIVIDUAL data stream is reassembled at the receiving end based on the timing. Synchronous TDM gives exactly the same amount of time to each connected device. It allocates time to every device even if a device has nothing to transmit. Thus, Synchronous Time Division Multiplexing is used to provide constant time DELAY. It can ALSO provide constant bandwidth.

Right option is (a) PACKET SIZE ALSO increases

Explanation: DISTANCE is directly proportional to packet size. So as distance increases packet size also increases.

The correct answer is (C) Pulse Code Modulation

Explanation: The difference between an input VALUE and its quantized value is called quantization error or we can also see it as that when an ANALOG number is not CONVERTED into an exact digital number. It takes place in pulse code modulation (PCM). Pulse Code Modulation is a TECHNIQUE in which the amplitude of an analog signal is converted to a binary value represented as a series of pulses.

The correct choice is (C) 0.036

Best explanation: ELECTRIC Field a region AROUND a charged PARTICLE or object WITHIN which a force would be exerted on other charged particles or objects.

The correct option is (d) 5

Explanation: Quantization is a process in which the continuous range of VALUES of an analog signal is sampled and DIVIDED into non-overlapping (but not necessarily equal) subranges, and a DISCRETE, unique value is assigned to each sub-range.

Therefore, number of PULSE in quantisation level =2^n = 32, so n = 5, where n = Quantization Level.

Right choice is (B) Common Emitter

The explanation: Common Emitter is most widely used because it has high POWER gain and voltage gain. In this method of connection, small changes in base/emitter CURRENT CAUSE large changes in collector/emitter current. Therefore, the circuit is that of a current amplifier. Moreover, it also provides maximum transconductance for a given load.

The correct answer is (c) 0.02

To elaborate: (mPc)/2 = Psb, wherem = Modulation Index, Pc = Carrier POWER and,

Psb = Power of each sideband

THEREFORE, (mVc ^2)/2 = Vsb 2^2 (Vc= 8000 V, and Vsb = 800)

Therefore, m = (800^2 X 2) / 8000^2 = 0.02.

Right answer is (d) disturbance CAUSED in nearby circuit due to transmitted signal

The explanation is: Crosstalk is a disturbance caused by the ELECTRIC or MAGNETIC fields of one telecommunication signal affecting a signal in an adjacent circuit. It is generally caused by undesired COUPLING. In a TELEPHONE circuit, crosstalk can result in the hearing part of a voice conversation from another circuit.

The CORRECT answer is (b) SSB-SC

To EXPLAIN I would SAY: SSB-SC modulation technique uses minimum BANDWIDTH as it suppresses the carrier and transmits either of the two side-bands while DSB-SC suppresses the carrier and transmits both the side-bands.

Right CHOICE is (a) envelope

The EXPLANATION: AM wave is represented by (A + XT)cos⁡ωc t or Etcos⁡ωc t, where xt is modulating SIGNAL, A is amplitude and therefore, Et is the envelope of the AM wave.

Correct CHOICE is (C) 0.33

Explanation: We know, Modulation INDEX(µ) = (Vmax-Vmin)/(Vmax+Vmin),

Where, Vmax = Maximum Amplitude of an amplitude MODULATED = 10V

Vmin = Minimum amplitudeof an amplitude modulated = 5V

Therefore, µ = (10-5)/(10+5) = 0.33.

Right choice is (a) 48kbPs

For EXPLANATION I WOULD say: Bit RATE refers to the rate at which data is processed or transferred. It is USUALLY measured in SECONDS, ranging from bps for smaller values to kbps and mbps.

Bit rate is also known as bitrate or data rate.

Bit rate, Rb = ^1⁄Tbwherewhere n = number of bits and fs = Sampling Frequency

Tb = 1/42, therefore Bit rate = 42 Kbps.

Right CHOICE is (c) 1536 KHz

The best EXPLANATION: N = 24, fm = 3.4 kHz

m = 128,

2^n = m = 128, n = 7

But fs = 2FM, where, fs = samplingfrequency

instead at 2fm2 x 3.4 kHz6.8 KHz.

B.W. = N(n+1)X fs= [24(7 + 1)] 8 kHz = 1536 KHz.

Right option is (c) 3.84W

The EXPLANATION is: MODULATION index = 0.4 and Pc = 96W. POWER in sidebands may be CALCULATED as

The CORRECT answer is (d) 6.25%

Explanation: MODULATION index = 0.5. POWER in sidebands MAY be CALCULATED as

The CORRECT choice is (a) 1.5Pc

The explanation: Total power, Pt = Pc (1 + ^µ^2⁄2),where Pc = CARRIER Power

where µ = 1 (for 100% modulation),

 so Pt = Pc(1 +(1^2/2)). On SOLVING it we GET Pt = 1.5Pc.

Right choice is (B) 14.28 bauds

To elaborate: The carrier SIGNAL is characterized by the number of signal intervals, or PULSES, that are transmitted per second. Each pulse is called a BAUD. BPS stands for bits per second. Bps is a measure of how many bits can be transmitted during one pulse (one baud).

The correct OPTION is (c) 0.77

Explanation: GIVEN that m1 = 0.75 and M2 = 0.2. Total MODULATION index will be equal toBy SUBSTITUTING values we havewhich is equal to 0.77.

Correct choice is (b) 384W

Explanation: TOTAL POWER, Pt = PC (1 + ^µ^2⁄2),where Pc = Carrier Power = 300W

where Modulation INDEX (µ) = 0.75,

So Pt,

Correct OPTION is (a) 66%

To explain I would say: In DSB-SC CARRIER is suppressed.

So Total Power required in DSBSC Modulation = (u^2XPc)/2 = Pc/2

In NORMAL AM, carrier is not suppressed.

So total power required in AM Modulation = (1+(u^2/2))XPc = 3Pc/2

Therefore, Power saving = ((Pc/2)/(3Pc/2)) x 100% = 66%.

Right answer is (c) 0.05

To elaborate: Field is a REGION around a charged particle or OBJECT within which a force WOULD be EXERTED on other charged particles or objects.