Subject: 2006 April Board Exam                                                                                                      set 1

Reviewer: kuging2001

 

Direction: Ang JRCS himo-himo lng ni nga review center para pakita-kita ky nani hehehe… ang mastermind amo si REX!!! Tapos nyo answer sang mga problems kindly text your answers sa pinakagwapo nga reviewer sang JRCS hehehehe joke joke joke!!! Answers will be check this coming Sunday 20 Nov 2005…so what are you waiting for? (This copy is very confidential)

 

  1. The total bandwidth needed for an AM signal at 55.25 MHz with 0.5 MHz video modulation is

A 0.25 MHz                  B 0.5 MHz                   C 1 MHz                      D 10 MHz

 

  1. The RF section of a radio transmitter generally consists of  

A Master oscillator                                          B Final power amplifier to feed antenna

C Buffer stage                                                 D All of the above

 

  1. In AM the modulation envelop has a peak value double the unmodulated carrier level, when the modulation is

A 25 %                         B 33 %                                    C 50 %                        D 100 %

 

  1. Which of the following is frequency is likely to be associated with AM radio broadcast ?

A 1000 kHz                  B 100 MHz                  C 500 MHz                  D 10 GHz

 

  1. The When a broadcast AM transmitter is 50% modulated , its antenna current is 12A . What will be the current when the modulation depth is increased to 90%?

A 12.9 A                       B 13.4 A                      C 16.6 A                      D 21.8 A

 

  1. A 1000 kHz carrier is simultaneously modulated with 300 Hz , 800 Hz and 2 kHz audio sin waves. The frequencies present in the output will be

A 998 kHz and 1002 kHz                               

B 998 kHz, 99.2 kHz, 10008 kHz, 1002.0 kHz

C 998 kHz, 999.2 kHz, 999.7 kHz, 1000.3 kHz,1000.8 kHz, and 1002.0 kHz,

D None of the above.

 

  1. A 360 W carrier is simultaneously modulated by two audio wave with modulation percentage of 55 and 65 respectively. the total side band power radiated will be 

A 180 W                      B 130 W                      C 60 W                        D 90 W

 

  1. A 200 W carrier is modulated to a depth of 75 % . The power of the modulated wave will be

A 128.1 W                   B 256 .2 W                  C 512.5 W                   D 886.6 W

 

  1. Which of the following receiver does not have amplitude limiter stage?

A AM                            B FM                            C Both AM & FM         D None of the above.

 

  1. Which of the following will carry the same information as the limiter stage?

A VSB only                                                      B VSB and SSB         

C VSB , SSB and DSB                                   D All of the above

 

  1. In AM if modulation index is more than 1 than

A The bandwidth will increase                        B There will be interference with other signals

C Efficiency of transmitter will increase         D The wave will get distorted.

 

  1. The In grid bias modulation system the power required for modulating amplifier ,

A is negligible low since grid is negative

B is small as compared to that for plate modulation

C is large as compared to that for plate modulation

D is almost the same as compared to that for plate modulation

 

  1. For a signal amplitude modulation to a depth of 100%  by a sinusoidal signal, the power is

A same as the power of unmodulated carrier

B twice as the power of unmodulated carrier

C four time the  power of unmodulated carrier

D 3/2time the  power of unmodulated carrier

 

  1. Audio frequency range lies between

A 20 Hz to 20 kHz                                           B 20 kHz to 200kHz

C 2MHz to 20MHz                                           D 20 MHz to 200 MHz

 

  1. Which of the following filter is generally used in SSB generation ?

A Active filter               B Mechanical filter       C LC filter                    D Crystal filter

 

  1. The purpose of pilot carrier in SSB is 

A To provide increase bandwidth                   B To reduce power consumption

C Improve noise immunity                              D Frequency stabilization.

 

  1. In FM the carrier deviation is determined by

A modulation voltage                                       B frequency

C either of the above                                       D non of the above

 

  1. In FM the carrier deviation is determined by

A modulation voltage                                       B frequency

C either of the above                                       D none of the above

 

  1. The percentage of modulation for 45 kHz deviation in the FM broadcast band will be

A 30 %                         B 45 %                                    C 60 %                        D 90 %

 

  1. A frequency multiplier stage should operate as

A Class A                    B Class B                    C Class C                   D either of the above

 

  1. Which of the following frequency is likely to be associated with FM radio broadcasting

A 90 Hz                       B 90 kHz                     C 900 kHz                   D 90 MHz

 

  1. For a FM wave carrier modulating frequency is 10kHz & bandwidth is 2 MHz . if the modulating signal amplitude is doubled , the bandwidth will be

A 0.5 MHz                    B 1 MHz                      C 2 MHz                      D 4 MHz

 

  1. FM broad cast band generally lies in

A LF                             B HF                            C VHF                         D UHF

 

  1. In FM

A noise decrease by increasing deviation     

B noise decrease by decreasing deviation

C noise decrease by marinating deviation constant

D none of the above

 

  1. A FM wave has bandwidth of 160kHz and modulation index of 7.5. the frequency deviation, will be

A 75 kHZ                      B 115 kHZ                   C 75 MHZ                    D115 MHZ

 

  1. Which one of the following is an indirect way of generating FM?

A Varactor modulator                                      B Armstrong modulator

C Reactance FET modulator                         D Reactance bipolar transistor modulator

 

  1. De-emphasis circuit is used

A prior to modulation                                      

B after modulation

C for de-emphasising high frequency component

D for de-emphasising low frequency component

 

  1. Foster seelay discriminator uses a

A single tuned circuit  

B double tuned circuit with primary and secondary tuned to the same frequency

C double tuned circuit with primary and secondary tuned to the different frequency

D none of the above

 

  1. The Different between PM & FM

A lies in the poorer audio response of phase modulation

B is too great to make the two systems compatible

C is purely theoretical because practically both are identical

D lies in the different definitions of the modulation index.

 

  1. In the spectrum of a frequency –modulation wave

A the carrier frequency disappear when the modulation index is large

B the amplitude of any side band depends on the modulation index

C the total number of sideband depend on the modulation index

D the carrier frequency cannot disappear.

 

  1. In pulse transmitter the ratio of time of time on to time off is called

A efficiency                  B duty cycle                C base                        D bandwidth

 

  1. While demodulating PCM , it is first converted into

A PAM                         B PPM                         C PWM           D none of the above.

 

  1. The signal to quantisation noise ratio in a PCM system depends on

A sampling rate                                               B number of the quantisation level

C message signal bandwidth                         D all of the above

 

  1. Which of the following pulse modulating system is analog ?

A PCM                         B PWM                        C Both (A) & (B)          D none of the above

 

  1. The signal –to-quantization noise ratio in a PCM system depends upon

A sampling rate                                               B number of quantization levels

C imformation signal bandwidth                     D none of the above

           

  1. The distance between the transmitting antenna and the point where the sky wave is first receiver after returning to the earth is known as

A line-of-sight distance                                   B skip distance

C radial distance                                             D effective distance.

 

  1. The S/N ratio appearing at the output of each channel in PAM is

A three times the input S/N                             B one and half  times the input S/N

C twice the input S/N                                      D none of the above.

 

  1. The use of non-uniform quantization leads to

A reduction in transmission bandwidth           B increase in maximum SNR

C increase in SNR for low level signals         D simplification of quantization process.

 

  1. The biggest disadvantages of PCM is

A its inability to handle analog signals            B the high error rate which its quantizing noise reduces

C its incompatibility with TDM                         D the larger bandwidth that are required for it.

 

  1. Companding is used  

A to overcome quantizing noise in PCM        

B in PCM transmitters, to allow amplitude limiting in the receivers  

C to protect small signal in PCM from quantizimg distortion

D in PCM receiver to overcome impulse noise.

 

  1. The basic limitations on the performance of the communication system

A noise                        B power                       C bandwidth                D both B & C

 

  1. Electrical noise is referred to as

A White noise              B Gaussian noise       D Pink noise                D Static Noise

 

  1. Man made noise occurs randomly at frequencies

A below 450 MHz                                            B between 30 Hz to 20 kHz

C above 500 MHz                                           D above 100 GHz

 

  1. Atmospheric noise is less severe at frequencies above

A 20 kHz                      B 20 MHz                    C 100 kHz                   D 10 GHz

 

  1. Solar noise is cyclical and reaches very annoying peak every

A 100 years                 B 11 years                   C 28 days                    D 11 months

 

  1. Space noise occurs at frequencies about

A 8 MHz to 1.5 GHz                                        B 4.5 MHz                  

            C 800 kHz to 1.5 GHz                                     D 100 MHz to 500 MHz

 

  1. Amplifier operating over a 4MHz bandwidth has a 100 ohms input resistance. It is operating at 27 degree Celsius, has a voltage gain of 200, and has an input signal of 5 microvolts. Determine the RMS noise output.

A 1 mV                        B 0.514 mV                 C 0.1 mV                     D 5.14 mV

 

  1. Excess noise is a low frequency effect and occurs at frequencies below 1 kHz. Which of the following is not an excess noise?

A flicker noise              B white noise              C pink noise                D 1/f noise

 

  1. A transistor amplifier has a measured S/N power of 10 at its input and 5 at its output. Calculate the noise figure.

A 30 dB                       B -3 dB                        C 6.24 dB                    D 3 dB

 

  1. A three stages amplifier system has a 3-dB bandwidth of 200 kHz determine by an LC tuned circuit at its input, and operates at 22 degree Celsius. Solve for the effective noise bandwidth.

A 0.314 MHz                B 3.14 MHz                 C 4.17 MHz                 D 8.17 MHz

 

  1. In photo-conductive effect, radiations of wavelength greater critical wavelength will

 A produce free electrons                               B not produce free electrons

 C emit electrons from the surface                 D produce protons.

 

  1. In a photo-transistor, the photo-current is generated at

 A emitter-base junction                                  B collector-base junction

 C either of the junction                                   D both of the junctions.

 

  1. Typical value of open-ckt voltage of a solar cell is

 A 10 mV                     B 100 mV                   C 0.5 mV                    D 1 mV

 

  1. In a solar cell the short ckt current or open ckt voltage is produced as sun's radiation falls on it because

 A majority carriers flow across the junction

 B minority carriers flow across the junction

 C carrier recombination takes place near the junctions

 D depletion layer gets reduced.

 

  1. A photo-diode is used in reverse bias because

 A majority swept are reverse across the junction    

 B only one side is illuminated

 C reverse current is smaller as compared to photo current

 D reverse current is large as compared to photo current

 

  1. Photo multipliers are based on the principle of 

 A pyro-electric effect                                      B secondary emission

 C photo-voltaic effect                                     D photo-conduction.

 

  1. The sensitivity of the human eye peaks at the

 A red part of the visual region of the spectrum

 B violet region

 C green area of the spectrum

 D white part of the spectrum.

 

  1. An LED source produces light when

 A the PN junction is reverse bias                   B the PN junction become hot

 C the depletion region becomes wider          D hole and electrons combine in the depletion region.

 

  1. Which of the following is not classified as a photoconductive device ?

 A a PN photodiode                                         B a PIN photodiode

 C a photo voltaic cell                                      D a phototransistor & a light dependent register

 

  1. Under normal operating conditions a GaAs LED will have a forward voltage between

 A 1.1 and 3 V              B 3.1 and 5 V             C 7.1 and 9 V             D 10.1 and 15 V

 

  1. A silicon controlled rectifier (SCR) is a 

 A unijunction device                                       B device with three junctions

 C device with four junctions                          D none of the above.

 

  1. A thyristor is basically

 A a combination of diac and transistor          B a combination of diac and triac

 C a set of SCRs                                            D PNPN device

 

  1. A PNPN device having two gates is

 A Diac                                   B Triac                                    C SUS                        D BCS

 

  1. Which of the following device incorporates a terminal for synchronizing purposes ?

 A Diac                                   B Triac                                    C SUS                        D none of the above.

 

  1. The advantage of thyristor over SCS is

 A Slow switching time and large VH              B Slow switching time and smaller VH

 C Faster switching time and smaller VH       D Faster switching time and large VH

 

  1. A thyristor equivalent of a thratron tube is a

 A diac                                                             B Triac                       

C silicon-controlled rctifier SCR                     D none of the above.

 

  1. A triac is a

 A 2 terminal switch                                        B 2 terminal bilateral switch

 C 3 terminal unilateral switch                                    D 3 terminal biderctional switch.

 

  1. The tripple frequency of a six phase half wave rectifier for 220 V , 60 Hz input will be ?

 A 2160 Hz                  B 720 Hz                    C 360 Hz                    D 60 Hz

 

  1. The minimum duration of pulse in a triggering system for thyristors should be at least

 A 10 ms                      B 10 us                       C 30 ms                     D 1 sec.

 

  1. As compared to oscillators, an inverter provides

 A low frequency output                                  B low voltage output

 C didtortion less output                                   D noiseless output

 

  1. The number of levels in a digital signal is

A Ten                           B One                          C Four                         D Two

 

  1. IN any flip-flop when the Q output is 1, what is the state of the Q(-) terminal ?

A 1                               B 0                               C Either 1 or 0             D It can not define.

 

  1. The slow turning of a potentiometer is

A Digital input                                                  B Analog out put         

C Nature of the output depend on voltage      D It depends on resolution of the potentiometer

 

  1. Which of the following can provide a digital signal?

A Slow change in the value of a resistor        B sinusoidal wave

C Square wave                                               D Gradual turning of a potentiometer.

 

  1. Decimal that converts from decimal to binary numbered is called

A Encoder                   B Decoder                   C CPU                         D Converter

 

  1. Which of the Following is not valid in binary system ?

A 0 * 0 = 0                   B 0 * 1 = 1                   C 1 * 1 = 1                   D 1 + 1 = 10

 

  1. Decimal 18.293 when converted into 10’s complement will become

A 81.707                      B 81.700                      C 82.777                     D 82.300

 

  1. Which logic gate is similar to the function of two parallel switches?

A AND                         B NAND                       C OR                           D NOR

 

  1. According to Boolean algebra which of the following relation is not valid

A X(-) = 1                     B X + Y = Y + X           C XY = YX                   D X + (Y + Z) = (X + Y ) + Z

 

  1. According to Boolean algebra which of the following relation is not valid ?

A X(YZ) = (XY)Z                                               B X (Y + Z ) = XY + XZ

C X +  XY =  X                                                 D X(X + Y) = 1

 

  1. (A + B(-) + A(-)B ) is the same as

A 0                               B 1                               C C                              D C(-)

 

  1. In Boolean algebra   A + A + A+ A +  …………+A  is the same as 

A 5A                             B nA                            C A                              D Infinity.

 

  1. In case of OR gate , no matter what the number of inputs ,we

A 1 at any input causes the output to be at logic 1

B 1 at any input causes the output to be at logic 0

C 0 at any input causes the output to be at logic 0

D 0 at any input causes the output to be at logic 1

 

  1. Which of the following is an inverter ?

A Common base amplifier                              B Common Collector amplifier

C Common emitter amplifier                          D All of the above

 

  1. An index register in digital computer is register to be used for

A Address modification                                   B For indirect address

C Storing one of the operands                        D Pointing to the stack address.

 

  1. How many flip-flops are needed for  a 4 bit counter ?

A Two                          B Three                       C Four                         D Eight

 

  1. The op.amp. is used in

A NAND Gate              B D/A converters        C Shift registers          D None of the above.

 

  1. Which family of logic circuits uses field effect transistors ?

A TTL                                                              B CMOS                     

C Both TTL and CMOS                                  D Neither TTL  nor CMOS

 

  1. The Integrated Injection Logic has higher density of integration than TTL because it

A does not require transistors with high current gain and hence they have smaller geometry

B uses compact bipolar transistors

C Does not require isolation diffusion

D use dynamic logic instead of static logic.

 

  1. A Schmitt trigger is a digital circuit that produces a ……………… output regardless of the input waveform

A Sinusoidal                B Trapezoidal              C Rectangular             D Triangular

 

  1. Which circuit is used for a clock generator

A A Free running MV                                       B JK flip-flop

C Either of  A or B Above                                D Neither  of  A or B Above

 

  1. The …………………is ultraviolet light erasable and electrically programmable 

A ROM                        B RAM                         C PROM                     D EPROM

 

  1. How many Flip-flop circuits are needed to divide by 16

A Two                          B Four                         C Eight                        D Sixteen

 

  1. A half adder includes

A a NAND gate with OR gate                          B a AND gate with XOR gate

C only And gate                                               D neither OR nor XOR nor AND.

 

  1. The fastest logic family used in high speed application is

A DTL                          B TTL                          C ECL                         D RTL

           

  1. MOS family that dominates the LSI field is

A PMOS                      B NMOS                      C CMOS                     D None of the above.

 

  1. 64K is 

A 6400                         B 64000                       C 65536                      D 64536

 

  1. A micro-computer has memory location from 0000 to FFF , each storing 1 byte , how many bytes can the memory story ?

A 12,333                      B 14,666                      C 16,384                     D 16,843

 

  1. A charge coupled device has

A Low cost per bit       B High cost per bit      C Low density             D None of the above.

 

100.In magnetic film memory, the memory element consists of

A Plated wires                                                 B Super conductive material

C Nickel iron alloy                                           Dopped aluminum.

 

 

Subject: 2006 April Board Exam                                                                                                      set 2

Reviewer: kuging2001

 

Direction: Ang JRCS himo-himo lng ni nga review center para pakita-kita ky nani hehehe… ang mastermind amo si REX!!! Tapos nyo answer sang mga problems kindly text your answers sa pinakagwapo nga reviewer sang JRCS hehehehe joke joke joke!!! Answers will be check this coming Sunday 20 Nov 2005…so what are you waiting for? (This copy is very confidential)

 

 

  1. Which of the following frequency bands fall under microwave frequency?

A UHF & SHF              B SHF & EHF              C UHF,SHF & EHF     D VLF,LF & MF

 

  1. The gain of a TWT is proportional to

A Length of tube                                              B type of input and output

C Non of the above                                         D bothe A and B

 

  1. The frequency determining portion of a magnetron is

A a resonant cavity                                         B a shorted line

C an open line                                                 D a cathode.

 

  1. The wavelength of microwaves at 100GHz will be

A 3 cm                         B 0.3 cm                     C 0.03 cm                   D 30 cm

 

  1. The term LASER is an abbreviation for

A Low amplification signal emitting radiowaves

B Last aligned sound emitting radiowaves

C Light amplification by simulated emission of radiation

D Light amplification by symmetric emission of radiation

 

  1. MASER finds application in

A Opto electronics                                          B Fiber optics

C Telephone                                                   D All of the above

 

  1. A device used for coupling microwave energy is known as

A transmitter               B resonator                 C waveguide               D loop

 

  1. The skin effect causes current to flow

A in the center of the conductor                      B near the surface of the conductor  

C through central core of the conductor         D uniformly through the conductor.

 

  1. In the waveguide the energy is propagated by

A Voltage different                                           B current variations

C varying magnetic fields                               D varying magnetic and electric  fields

 

  1. Materials generally preferred for waveguides are

A brass and aluminium                                   B cast iron and steel

C nono-metallic solids including plastic         D highcarbon steel and vanadium steel.

 

  1. Which of the follow statement is incorrect?

A Waveguides are used to minimize skin effect at microwave frequencies

B Arectangular waveguide serves as a high pass filter

C TE10 is the dominant mode for co-axial cable

D All of the above

 

  1. When the microwave follow the curvature of the earth this is known as

A the farady effect                                           B ducting                    

C tropospheric scatter                                                D ionospheric refelection

 

 

  1. The main advantage of the two hole directional coupler is

A low directional coupling                               B poor directivity        

C high SWR                                                    D narrow bandwidth

 

  1. Which of the following microwave tube amplifier uses an axial magnetic field and radial electric field ?

A Coaxial magnetron                                      B CFA

C Travelling wave magnetron                         D Reflex klystron.

 

  1. Microwave link repeater are typically 50 km apart

A because of atmospheric attenuation           B because of earth's curvature

C because of output tube power limitations   D to ensure that the applied dc voltage is not excessive.

 

  1. A duplexer is used

A to couple two different antennas to transmitter without mutual interference

B to allow the one transmission without mutual interference

C to prevent interference between two antennas when they are connected to a receiver

D to increase the speed of the pulses in pulses radar.

 

 

  1. Which of the follow is unlikely to be used as a pulsed device ?

A TWT                         B CFA                         C BWO                       D Multi-cavity klystron.

 

  1. The parabolic reflector is  ( Indicate the false statement.)

A Omni-directional antenna                           

B Pencil beam antenna

C Popularly used antenna in terrestrial line-of-sight communication

D Not a broad cast antenna.

 

  1. One of the reasons why vacuum tubes eventually fall at microwave frequencies is that their

A noise figure increases                                

B transit time becomes too short

C shunt capacitance reactance become too large

D series inductive reactances become too small.

 

  1. Transit time in microwave tubes will be reduced if  (Indicate the false statement.)

A The electrodes are brought closer together

B A higher anode current is used

C Multiple or coaxial leads are used

D The anode voltage is made larger.

 

  1. Which of the following constitues an active component ?

A Semiconductor device                                 B Resistors

C Capacitors                                                   D  Inductor

 

  1. Which of the following is an active device ?

A Transormer                                                  B Silicon controlled rectifier

C Electric bulb                                                            D Loudspeaker

 

  1. The conductivity of materials found in nature range from 109ohm-1m-1 to nearly 10-18ohm-1m-1   From  this it can be concluded that the conductivity of selicon in ohm-1cm-1

A 0.5 * 10-15               B 0.5 * 10-21               C 0.5 * 10-3                 D 0.5 * 10-4

 

  1. The process by which impurities are added to a pure semiconductor is

A Diffusing                   B Drift                          C Mixing                      D Doping

 

  1. Which of the following is a passive component ?

A Semiconductor device                                 B Vacuum tube device

C Capacitors                                                   D All of the above

 

  1. The advantage of transistor over vacuum tube is

A no heat is required                                       B small size and light in weight

C very low power consumption                      D all of the above.

 

  1. A collector collects

A electrons from the base in case of PNP transistor

B electrons from the emitter in case of PNP transistor

C hole from the base in case of NPN   transistor

D hole from the base in case of PNP  transistor

 

  1. In a PNP transistor , with normal bais

A the collector junction has negligible resistance

B only holes cross the collector junction

C the collector-base junction is reverse baised and the emitter base junction is forward baised

D only majority carriers cross the collector junction.

 

  1. In most transistor the collector region is made physically larger than the emitter region   

A for dissipating heat                                      B to distingush it from other regions

C as it is sensitive to untra violet rays            D to reduce resistance in the path of flow of electrons.

 

  1. Aging effect exists in   

A Vacuum tube only                                        B transistors only

C Vacuum tube and transistors only              D none of the above

 

  1. A vacuum tube has electrodes confined inside an evacuated

A glass envelop only                                       B metal envelope only

C either of (A) or (B) above                             D none of the above.

 

  1. In which of the following application vacuum tubes are still being used

A Public address system                                B Radio receiver

C Radio transmitter                                        D Electroplating plants.          

 

  1. Vacuum tubes in a radio transmitter are used to

A provide dc supply                                         B generate high power radio waves

C record programs                                         D provide lighting inside the studio.

 

  1. Transistors have not replaced vacuum tubes because

A transistor are non-linear                             

B transistor do not have grid

C high power transistor operation and availablity are very difficult

D heat dissipation from transistor is difficult.

 

  1. Vacuum tubes are still used in some electronic device due to

A their long life                                     B their trouble free life

C their capacity to handle high power            D their batter reliability .

 

  1. Which of the following device has Characteristic close to that of an ideal voltage source

A Zener diode              B Vacuum diode         C Crystal diode           D All of the above.

 

  1. Which of the following  device has characteristics close to that of an ideal current source ?

A Gas diode                                                    B Crystal diode          

C Transistor in CB mode                                D All of the above..

 

  1. Avalanche break down in a semiconductor diode occurs when

A the potential barrier is reduced to zero        B forward bias exceeds a certain value

C reverse bias exceeds a certain value         D forward current exceeds a certain value.

 

  1. Which of the following material finds application in light emitting diodes?

A Silicon                      B Phosphorous           C Sulphur                    D Gallium phosphide.

 

  1. Which of the following material is used for infra-red LED's ?

A Gallium arsenide      B Calcuim phosphide C Silicon                      D Non of the above.