Placement Papers: BHEL Placement Paper 2006
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Consider the following expressions indicating the step or impulse response of an initially relaxed control system

(5 4e − 2 + ) u (t)

(e − 2t + 5) (u (t) )

V (t) + 8e − 2t u (t)

V (t) + 4e − 2t 4 (t)


Which is the following relate to rational transfer function of a system

Ratio of Fourier transform of output to input with zero initial conditions.

Ratio of Laplace transform of output to input with zero initial conditions.

Laplace transform of system impulse response.


Laplace transform of system unit step response select the correct answer using the codes given belowCodes

1 and 4

2 and 3

1 and 3

2 and 4


For the signal g (t) 10 cos (50 pt) cos2 (150at) The Nyquist sampling state in t seconds is

150 samples per second

200 samples per second

300 samples per second

350 samples per second


In the case of a 70 MHz 1F carries for a transponder band width of 36 MHz; energy must lie between MHz.

34 and 106

52And 88

106 and 142

34 and 142


Radar used to eliminate clutter in navigational application is

Pulse radar

Tracking radar

MTI radar

Mono pulse radar


The 1.55 mm windows is not yet in use with fiber optic systems because

The attenuation is higher than at 0.85 mm

The attenuation is higher than at 1.3mm

Suitable laser devices have not yet been developed

It does not lend itself to wavelength multiplexing


Preemphasis in FM systems involves

Compression of the modulating signal

Expansion of the modulating signal

Amplification of lower frequency components of the modulating signal.

Amplification of higher frequency components of the modulating signal.


In a terrestrial microwave system transmission of signals is achieved through

reflection from the ionosphere

line of sight mode

reflection from the ground

diffraction from the stratosphere.


Casse grain feed is used with a parabolic reflector to

increase the gain of the system

increase the bandwidth of the system

reduce the size of the main reflector

allow the feed to be placed at a convenient point.


In most microwave communication link rain drop attenuation is caused due to

scattering of microwaves by water drops of specific size.

scattering of microwaves by a collection of droplets acing as a single body.

absorption of microwaves by water and consequent heating of the liquid

absorption of the microwaves by water vapor in the atmosphere.


When a (75 j40) W load is connected to a coaxial line of Z0 = 75 W at 6MHz then the load matching on the line can be accomplished by connecting

A short circuited stub at the load

An inductance at the load

A short circuited stub at a specific distance from the load

none of the above


As compared to analog multimeters, digital Multimeters's are

less accurate

more accurate

equally accurate

none.


When a signal of 10 mV at 75 MHz is to be measured then which of the following instruments can be used

VTVM

Cathode ray oscilloscope

Moving iron voltmeter

Digital multimeter


Amplifier of class B has high theoretical efficiency of 78.5 percent because

It is biased almost to saturation

Its quiescent current is low

It's output is an exact replica of it's input

It is biased well below cut off


The coupling that produces minimum interference with frequency response is

Direct coupling

Impedance coupling

R C coupling

Transformer coupling


A superconductor is a

A material showing perfect conductivity and Meissner effect below a critical temperature

A conductor having zero resistance

A perfect conductor with highest dimagnetic susceptibility

A perfect conductor which becomes resistance when the current density through it exceeds a critical value


When an inductor tunes at 200 KHz with 624 pF capacitor and at 600 KHz with 60.4 pF capacitor then the self capacitance of the inductor would be

8.05 pF

10.05pF

16.01pF

20.01pF


The Q of a radio coil

is independent of frequency

increases monotonically as frequency increases

decreases monotonically as frequency increases

increases upto a certain frequency and then decreases beyond that frequency


When a generator of internal impedance and operating at 1GHz feeds a load via a coaxial line of characteristic impedance 50 ohm then the voltage wave ratio on the feed line is

0.5

1.5

2.5

1.75


The coding system typically used in digital telemetry is

PPM (pulse position modulation)

PAM (pulse amplitude modulation)

PCM (pulse code modulation)

PDM (pulse duration modulation)


Radiation pyrometers are used for the measurement of temperature in the range of

2000C to 5000C

00C to 5000C

5000C to 12000C

12000C to 25000C


RF amplifier of an A. Mreceiver is normally biased in

Class ‘A’

Class ‘b’

Class ‘C’

None


The value of gate voltage for the operation of enhancement of only N channel MOSFET has to be

High positive

High negative

Low positive

Zero
