PRE-BOARD EXAMINATIONS

Infinite Impulse Response (IIR) filter

What filter can potentially continue to produce output indefinitely even after the input has stopped?

2.2 μm

In a single-mode fiber cable, determine the maximum allowable diameter of the core for light frequency of 300 THz and numerical aperture of 0.35.

It is much longer

How does the range of sky-wave propagation compare to ground-wave propagation?

ASK

Which of the following gives maximum probability of error?

Channel decoder

The figure below shows a simple block diagram of a digital communication system. Which block recreates incoming binary sequence?

33.33%

Detemine the sideband power percentage of AM system assuming 100% modulation and with carrier and total power of 100 W and 150 W respectively.

All of the choices

In circuit switching, which of the following can be adopted as a dedicated path between the source and destination?

The step size remains same and the quantizer has linear characteristics.

In uniform quantization process:

Session

What layer in the Open Systems Interconnection (OSI) model handles the management and synchronization of the data transmission?

All of the choices

Industrial safety management is that branch of mangement which is concerned with ____ hazards form the industries.

the suppressed carrier must be replaced for detection

A receiver designed for SSB reception must have a BFO (beat frequency oscillator) because:

100 %

In the case of CDMA, what frequency reuse is totally possible?

It increases.

What happens to the feed point impedance of a ground-plane antenna when its radials are changed from horizontal to downward-sloping?

low

Material with ____ specific heat will heat up more rapidly in fire conditions.

always smaller or equal to the bit rate

In digital data transmission, baud rate is:

Tinder

Combustible solids with specific surface of more than 20 cm^2/gm is termed as:

Serial transmission

Which type of data transmission whereby the Least Significant Bit (LSB) is usually transmitted first and the Most Significant Bit (MSB) the last?

31.07 dB

If the occupied baseband of white noise test signal is 60 - 4028 kHz, determine the bandwidth ratio.

maximum usable frequency

If we transmit a signal, the frequency of which is so high we no longer receive a reflection from the ionosphere, the signal frequency is above the:

15 times greater

The typical value of attenuation in a coaxial cable is: 3 dB/km. In a fiber optic cable, it is 0.2 dB/km. How many times greater is the attenuation per km in coaxial cable than that in fiber optic cable?

An impedance-matching device

What would you use to connect a coaxial cable of 50 ohms impedance to an antenna of 17 ohms impedance?

master oscillator

In a CW transmitter, the output from the __________ is connected to the driver/buffer.

1-mV; 0.514-mV

An amplifier operating over a 4-MHz bandwidth has a 100-Ω input resistance. It is operating at 27°C, has a voltage gain of 200, and has an input signal of 5 μV rms. Determine the rms output signals (desired and noise), assuming external noise can be disregarded.

It provides good signal plus noise to noise ratio at low RF signal levels

Why is FM voice best for local VHF/UHF radio communications?

0

In digital communications, what is the cross-correlation present between the two users of any given ideal TDM system?

14 μH

The value of capacitance of a varactor at the center of its linear range is 40 pF. This varactor will be in parallel with a fixed 20-pF capacitor. What value of inductance should be used to resonate this combination to 5.5 MHz in an oscillator?

2B + D

What is the primary rate for ISDN system?

is less at higher frequencies

The distance travelled by ground waves:

Out-of-channel emissions

What is the result of over deviation in an FM transmitter?

Least Significant Bit (LSB)

What bit is usually transmitted first in serial type of data transmission?

2 bits

If the probability of a message is 1/4, then the information in bits is:

sensitivity, selectivity and stability

The three main parameters against which the quality of a receiver is measured are:

Increased bandwidth

The main advantage of broadband communication system over narrow band communications is:

10

A transmission system using a TE₁₀ mode waveguide of dimensions a = 5 cm, b = 3 cm is operating at 10 GHz. The distance measured between two minimum power points is 1mm on a slotted line. Calculate the VSWR of the system.

15 kHz

Determine the bandwidth of an FM signal with 5 kHz maximum frequency deviation and 2.5 kHz maximum modulating frequency. Use Carson's rule.

It brings the feed point impedance closer to 50 ohms

What is an advantage of downward sloping radials on a ground plane antenna?

can be the same for different diameter line

The characteristic impedance of a coaxial line:

A fairly good impedance match

What does an SWR reading of less than 1.5:1 mean?

An area which is too far away for ground-wave propagation, but too close for sky-wave propagation.

What is a skip zone?

Channel encoder

In a simple digital communication system, if the source encoder converts the source output to binary sequence which of the following, processes the binary sequence for transmission?

31.83 m

For an antenna in a form of a linear conductor or an array of conductors, calculate the effective length at 3 MHz.

B-ISDN

Which of the following is based on Asynchronous Transfer Mode (ATM) technology?

2 Mbps

A network with bandwidth of 10 Mbps can pass only an average of 12,000 frames per minute with each frame carrying an average of 10,000 bits. What is the throughput of this network?

The SWR may be too high, or the transmission line loss may be high

If your antenna transmission line gets hot when you are transmitting, what might this mean?

A shift in the input signal also results in the corresponding shift in the output.

A system is said to be shift invariant only if:

Only if the value of an impulse response is zero for all negative values of time.

Which condition determines the causality of the linear time-invariant (LTI) systems in terms of its impulse response?

Between peer entities

In Protocol Data Units (PDUs), where does the data get interchanged?

Correlation receiver

In coherent demodulation technique of FSK, signal can be affected using:

Layer 2

What layer divides the bit stream received from the network layer into manageable data units called frames and transforms the physical layer to a reliable link by adding mechanism to detect and retransmit damaged frames?

The ratio of the diameter of the inner conductor to the diameter of the outer shield

What factors determine the characteristic impedance of a coaxial antenna transmission line?

The Polar signaling

Alternate Mark Inversion (AMI) signaling is acknowledged as:

Address

The preamble in time division multiple access (TDMA) frame contains:

individual, individual

Frequency division multiple access (FDMA) assigns ______ channels to _______ users.

The antenna is the wrong length for the operating frequency, or the transmission line may be open or short circuited

What does a very high SWR reading mean?

Character Stuffing

Which type of framing technique reduces the problem of synchronization of the receiver?

Occupant load

The _____ is the number of square feet of floor area required per occupant.

Channels 1, 6, and 11 are the only three channels with frequencies that do not overlap.

On an IEEE 802.11b/g/n wireless network running at 2.4 GHz with multiple access points, the traditional best practice is to use channels 1, 6, and 11, with no two adjacent access points configured to use the same channel. Which of the following is the real reason why this is a good plan?

slightly lower

The optimum working frequency provides the best long range HF communication. Compared with the maximum usable frequency (MUF), it is usually:

low pass filters

BPSK signal can be demodulated by using:

FDM

In digital communications, which of the following multiplexing schemes is based on orthogonality?

equal to the pure resistance which, if connected to the end of the line, will absorb all the power arriving along it

The characteristic impedance of a transmission line is:

Network

In TCP/IP, the ____layer is responsible for creating a connection between the source computer and the destination computer.

Only if bounded input generates unbounded output

Under which conditions does an initially relaxed system become unstable?

Class B

Flammable liquids having flash point of 23°C and above but below 65°C is ______ liquid.

QPSK

In which of the following systems where a bit stream would be portioned into an even stream and an odd stream?

In Phase Shift Keying

Which of the following gives the least probability of error?

so that one antenna can be used for transmitter and receiver

An antenna changeover switch in a transmitter-receiver combination is necessary:

RZ-AMI

What channel encoding technique whereby successive binary "1" bits in the bit stream are transmitted with alternation polarity?

BP-AMI-RZ

Which is the most commonly used line coding format with best overall desirable properties?

Capture effect

FM receivers perform in an unusual manner when two or more stations are present. The strongest signal, even though it is only two or three times stronger than the other signals, will be the only transmission demodulated. This is called:

Voice traffic

Which among the following utilizes the transmission line up to 85 - 95 %?

26.5 W/m^2

Determine the power density required to produce an electric field strength of 100 volts per meter in air.

physical dimensions and relative positions of the conductors

The characteristic impedance of a transmission line is determined by the:

It is greater.

How does the bandwidth of a folded dipole antenna compare with that of a simple dipole antenna?

balanced modulator

In a single sideband transmitter, the output of the ____________ is connected to the filter.

Width of each pulse decreases.

As the signaling rate increases:

6:1

If the center impedance of a folded dipole is approximately 300 ohms, and you are using RG8U (50 ohms) coaxial lines, what is the ratio required to have the line and the antenna matched?

Sampling

What property of delta function indicates the equality between the area under the product of function with shifted impulse and the value of function located at unit impulse instant?

Layers 1 to 3

Under the Open System Interconnection (OSI) hierarchical model which of the 7 layers deal with physical aspects of moving data from one device to another?

QPSK

If the maximum instantaneous phase transition of a digital modulation techniques kept at 90°, the modulation will be organized as:

Not equal to zero

What would be the joint probability of statistically independent events that occur simultaneously?

Sky-wave propagation

When a signal is returned to Earth by the ionosphere, what is this called?

1 and 2

A Laplace transform exists when:

1. The function is piecewise continuous.

2. The function is of exponential order.

3. The function is piecewise discrete.

4. The function is of differential order.

Mesh

In what topology where every device has a dedicated point-to-point link to every other device?

skip distance

The distance from the transmitter to the nearest point where the sky wave returns to the Earth is called the:

overdriven stages

In a transmitter, excessive harmonics are produced by:

power amplifier

In a frequency modulation transmitter, the _________ is located between the frequency multiplier and the antenna.

About the changes in sample value

The basic principle of differential coding techniques like Differential PCM (DPCM) and Adaptive Differential PCM (ADPCM) is to transmit information:

Continuous in nature

The characteristics of compressor in μ-law companding is:

26.9 kbps

What is the Shannon limit for information capacity for a standard voice band communications channel with a signal-to-noise ratio of 30 dB and a bandwidth of 2.7 kHz?

A notch filter

What kind of filter would you use to attenuate an interfering carrier signal while receiving an SSB transmission?

Guard

What bits are utilized to allow synchronization of the receivers between different slots and frames?

It would be increased by 100%

If the length of coaxial transmission line is increased from 20 metres (66 ft) to 40 metres (132 ft), how would this affect the line loss?

Because it is the highest ionospheric region

Why is the F2 region mainly responsible for the longest distance radio-wave propagation?

Frequencies up to 40 MHz or even higher become usable for long-distance communication

When sunspot numbers are high, how is propagation affected?

1.2208 ms

On a 10 Mbps Ethernet packet format, how fast can a 1500-byte block of data be transmitted?

By installing a suitable filter at the receiver.

How can intermodulation be reduced?

50 ohms coaxial cable

Which of the following transmission lines will give the best match to the base of a quarter-wave ground-plane antenna?