REM C LVL 3

Question 1

What kind of antenna feed line is made
of two conductors held apart by insulated rods?

A. Coaxial cable
B. Twin lead in a plastic ribbon
C. Open-conductor ladder line
D. Twisted pair

Answer 1

C. Open-conductor ladder line

‘Feed line’ is synonym for transmission line. “Two wires held apart by insulating rods (spacers or ‘spreaders’)” is also known as ‘open wire line’ or ‘ladder line’.

Question 2

What common connector usually joins
RG-213 coaxial cable to an HF
transceiver?

A. A PL-259 connector
B. A binding post connector
C. An F-type cable connector
D. A banana plug connector

Answer 2

A. A PL-259 connector

‘RG-213’ is the catalogue designation of
common 10mm (0.405 in.) coaxial
cable. ‘PL-259’ is the catalogue
designation of the male connector
which matches the output connector
found on MF/HF (Medium Frequency/
High Frequency) transceivers. The ‘BNC
connector is found on larger size
handheld transceivers. The ‘Type-N connector is the connector of choice above 300 MHz.

Question 3

On the VHF and UHF bands, polarization
of the receiving antenna is very
important in relation to the transmitting antenna, yet on HF bands it is relatively unimportant. Why is that so?

A. The ionosphere can change the
polarization of the signal from moment
to moment
B. Anomalies in the earth’s magnetic field
produce a profound effect on HF
polarization
C. The ground wave and the sky wave
continually shift the polarization
D. Greater selectivity is possible with HF
receivers making changes in polarization
redundant

Answer 3

A. The ionosphere can change the
polarization of the signal from moment
to moment

As a radio wave travels through the
changing layers of the ionosphere and
is refracted back to Earth, wave
polarization will have changed.

Question 4

The difference between DC input power and RF output power of a transmitter RF amplifier:

A. appears as heat dissipation
B. is due to oscillating
C. is lost in the feed line
D. radiates from the antenna

Answer 4

A. appears as heat dissipation

Power Amplifiers have a certain
lefficiency’, the ratio of DC power
required to obtain an RF output. The difference goes up in heat. This is the reason for the ‘heat sinks’ on the back of transmitters.

Question 5

A microwave transmission line
constructed of a center conductor
suspended between parallel conductive
ground planes

A. stripline
B. coax
C. waveguide
D. Microstrip

Answer 5

A. stripline

Question 6

Polarization change often takes place
on radio waves that are propagated over long distances. Which of these does not cause polarization change?

A. Parabolic interaction
B. Reflections
C. Passage through magnetic fields (Faraday
rotation)
D. Refractions

Answer 6

A. Parabolic interaction

NOT. Refraction, reflection and
magnetic fields all affect wave
polarization as waves travel to and from
the ionosphere.

Question 7

The usual effect of ionospheric storms
is to:

A. increase the maximum usable frequency
B. prevent communications by ground wave
C. cause a fade-out of sky-wave signals
D. produce extreme weather changes

Answer 7

C. cause a fade-out of sky-wave signals

lonospheric Storm: exceptional solar
activity where greater quantities of
particles arrive from the Sun make for
more ionization (too much ionization),
absorption is increased and may last for
days.

Question 8

What effect does tropospheric bending
have on 2-metre radio waves?

A. It causes them to travel shorter distances
B. It lets you contact stations farther away
C. It reverses the sideband of the signal
D. It garbles the signal

Answer 8

B. It lets you contact stations farther away

BENDING. Tropospheric bending
refraction occurs when a wave travels through masses of differing densities(humidity content) in the troposphere.The wave travels further rather than escape right away into space.

Question 9

Why is a loading coil often used with an
HF mobile vertical antenna?

A. To lower the Q
B. To tune out capacitive reactance
C. To improve reception
D. To lower the losses

Answer 9

B. To tune out capacitive reactance

Short answer: a coil (inductor) has a
behaviour totally opposite to capacitors; cancelling reactive capacitance’ makes sense. A short antenna (e.g., 2.5m)
operated on HF frequencies
(wavelengths of 10 to 80 metres) looks like an antenna operated well below its natural resonant frequency. If you think of an ideal antenna as a resonant circuit where capacitive and inductive reactances cancel each other, you’l
note that CAPACITIVE reactance (XC=1 over ‘2PIf*C’) grows below the resonant frequency. A “loading coil” cancels out that capacitive reactance.

Question 10

What is the low angle radiation pattern of an ideal half-wavelength dipole HF antenna installed parallel to the earth?

A. It is a circle (equal radiation in all
directions)
B. It is a figure-eight, off both ends of the
antenna
C. It is two smaller lobes on one side of the antenna, and one larger lobe on the other side
D. It is a figure-eight, perpendicular to the
antenna

Answer 10

D. It is a figure-eight, perpendicular to the
antenna

Picture a horizontal dipole viewed from above. If you plotted radiation all around it, the plot would look like a “number eight”: peak radiation at 90 degrees (broadside) from the antenna, negligible
radiation from the ends.

Question 11

Why is a Yagi antenna often used for
radiocommunications on the 20-metre
band?

A. It provides excellent omnidirectional
coverage in the horizontal plane
B. It helps reduce interference from other
stations off to the side or behind
C. It is smaller, less expensive and easier to
erect than a dipole or vertical antenna
D. It provides the highest possible angle of
radiation for the HF bands

Answer 11

B. It helps reduce interference from other
stations off to the side or behind

20-metre is an amateur band with global
reach. It is open during day time even
during solar cycle lows. The directive
antenna pattern of a Yagi permits
reducing interference by focusing
energy in one direction only.

Question 12

In a waveguide, it is a field made up of magnetic lines of force that are caused by current flow through the conductive material of the waveguide. The strength of the field is indicated by the number of H lines in a given area, varies directly with the amount of current.

A. H field and Magnetic field
B. H field
C. E field
D. Magnetic field

Answer 12

A. H field and Magnetic field

Magnetic lines of force, called H lines,are continuous closed loops. All of the H lines associated with the current are collectively called a magnetic field or H field. The strength of the H field, indicated by the number of H lines in a
given area, varies directly with the
amount of current.

Question 13

Electromagnetic energy transmitted into space consists of electric and magnetic fields that are at right angles (90 degrees) to each other and at right angles to the direction of propagation. A
simple analogy to establish this
relationship is by use of the right-hand rule for electromagnetic energy, based on the ____

A. Wavefronts
B. POYNTING Vector
C. Electromagnetic fields
D. Pointing vector

Answer 13

B. POYNTING Vector

It indicates that a screw (right-hand
thread) with its axis perpendicular to the
electric and magnetic fields will
advance in the direction of propagation
if the E field is rotated to the right
(toward the H field).

Question 14

In laser transmission, which describe
how much of the range from laser to
quiescent bias point to cut-off is taken
by the signal?

A. Quiescent index
B. Optical modulation index
C. Bias index
D. Optical dispersion index

Answer 14

B. Optical modulation index

Question 15

The waveguide yields an electric field
configuration known as

A. Triangular wave electric distribution
B. Square wave electric distribution
C. Full-sine electric distribution
D. Half-sine electric distribution

Answer 15

D. Half-sine electric distribution

The waveguide yields an electric field
configuration known as the half-sine
electric distribution. This configuration is also called a MODE OF OPERATION. Note that the strength of the field is indicated by the spacing of the lines; that is, the closer the lines, the stronger
the field. The regions of maximum
voltage in this field move continuously
down the waveguide in a sine-wave
pattern. To meet boundary conditions, the field must always be zero at the “b”walls.

Question 16

The travel of energy down a waveguide is similar, but not identical, to the travel of electromagnetic waves in free space.The difference is that the energy in a waveguide is confined to the physical
limits of the guide. Two conditions,
known as _____ , must be satisfied for
energy to travel through a waveguide.

A. Boundary conditions
B. Central conditions
C. Magnetic field pattern
D. Zero-current points

Answer 16

A. Boundary conditions

Question 17

It is only one of many field
configurations, or modes, that can exist
in a rectangular waveguide.

A. Half-square wave field
B. Full-sine field
C. Full-square wave field
D. Half-sine field

Answer 17

D. Half-sine field

A full-sine field can also exist in a
rectangular waveguide because the field
is zero at the “b” walls.

Question 18

The ____ is an association that
sponsors the use of infrared waves.

A. FCC
B. IrDA
C. PUD
D. EIA

Answer 18

B. IrDA

Question 19

Also known as EPON (Ethernet passive optical network) or EFM (Ethernet in the first mile). A protocol for FTTH developed by the lEEE.
It is used extensively in Asia and in other parts of the world. It features symmetrical wire rates of 1.25 Gb/s.

A. GE-PON Gigabit Ethernet passive
optical network
B. FTTC Fiber-to-the-curb
C. BPON Broadband passive optical network
D. GPON Gigabit passive optical network

Answer 19

A. GE-PON Gigabit Ethernet passive
optical network

Question 20

Inductive sensors are also referred to as
“NMR” coils. What does NMR stand for?

A. Nuclei Magneto Resonance
B. Nuclei Magnetic Resonator
C. Nuclear Magnetic Resonator
D. Nuclear Magnetic Resonance

Answer 20

D. Nuclear Magnetic Resonance

Inductive proximity sensor:

• An inductive proximity sensor can
only detect metal targets.

• This is because the sensor utilize an
electromagnetic field.

• When a metal target enters the
electromagnetic field, the inductive
characteristics of the metal change the
field’s properties

• Thereby alerting the proximity snesor
of the presence of a metallic target.

• Depending on how inductive the
metal is, the target can be detected at
either a greater or shorter distance.

• Inductive sensors are also referred to
as NMR(Nuclear Magnetic Resonance).

Question 21

Capacitive transducers cannot be used
as strain gauges.

A. True
B. False
C. Partly false
D. Partly true

Answer 21

B. False

Strain to be measured is applied to
parallel plates of a capacitor and total
displacement change will be
proportional to strain.

Question 22

Which of the following represents
drawback of the inductive transducer
for displacement measurement?

A. None of these choices
B. Lower sensitivity
C. Requirement of large displacement
D. Act of electromagnetic force of
attraction

Answer 22

D. Act of electromagnetic force of
attraction

Electromagnetic force of attraction is
acted on moving core, and hence
displacement source has to overcome
this force.

Question 23

Which if the following is NOT an application of capacitive element sensors?

A. Pollution detection
B. Level control of Liquids
C. Metrology application to measure shape
errors
D. Small vessel pump control

Answer 23

A. Pollution detection

Question 24

Statement (I): Capacitive proximity
sensor can only be used for the
detection of metal objects and is best
with ferrous metals.

Statement (II): One forms of capacitive
proximity sensor consists of a single
capacitor plate probe with the other
plate being formed by the object, which
has to be metallic and earthed.

A. Both Statement (l) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
B. Both Statement (1) and Statement (Il) are individually true but the Statement (II) is not the correct explanation of Statemen (I)
C. Statement (I) is true but Statement (II) is
false
D. Statement (I) is false but Statement (II)
is true

Answer 24

D. Statement (I) is false but Statement (II)
is true

One form of capacitive proximity sensor
consists of a single capacitor metallic
and earthed figure. As the object
approaches so the plate separation’ of
the capacitor changes, becoming
significant and detectable when the
object is close to the probe. Magnetic
field proximity sensors are relatively
simple and can be made using a
permanent magnet. The magnet can be made a part of object being detected or can be part of the sensor device. It can only be used for the detection of metal object and is best with ferrous metal.

Question 25

Which of the following is correct for
moisture transducers?

A. None of these choices
B. Dielectric constant of pure water and of
other materials are equal
C. Dielectric constant of pure water
greater than other materials
D. Dielectric constant of pure water much
less than other materials

Answer 25

C. Dielectric constant of pure water
greater than other materials

Dielectric constant of pure water is 80
which is much greater than other
materials, this characteristic helps in
measurement of moisture content.

Question 26

Input transducers and inverse
transducers are the same.

A. False
B. Partly true
C. True
D. Partly false

Answer 26

A. False

Input transducers are devices which
convert non-electrical quantity to
electrical quantity and Inverse
transducers are devices which convert
electrical quantity to non-electrical
quantity.

Question 27

Which of the following cannot act as
inverse transducer?

A. Quartz
B. Barium titanate
C. Cadmium
D. Lead zirconate

Answer 27

C. Cadmium

Quartz, Barium titanate and Lead
zirconate are piezo electrical
substances which are known for its
ability to act as inverse transducers.

Question 28

RAID-1 is also known as mirroring

A. Partly true
B. True
C. False
D. Partly false

Answer 28

B. True

RAID stands for redundant array of
independent disks. RAID-1 is also called mirroring as one disk is a safety back-up for the other disk. It is the main
advantage of the RAID-1 level. All the
data written to one disk is copied
continuously to the disk two. It is a
simple and very effective way of
protecting valuable data.

Question 29

In memory-mapped scheme, the
devices are viewed as

A. distinct 1/0 devices
B. only output devices
C. memory locations
D. only input devices

Answer 29

C. memory locations

In memory-mapped scheme, the
devices are viewed as memory
locations and are addressed likewise.

Question 30

A robot is a

A. Machine that replaces a human by
performing complex mental processing
tasks
B. Type of virtual reality device that takes the
place of humans in adventures
C. Computer-controlled machine that mimics the motor activities of living things
D. Machine that thinks like a human

Answer 30

C. Computer-controlled machine that mimics the motor activities of living things

Robots are computer-controlled machines that mimic the motor activities of living things.

Question 31

While performing read operation, one
must take care that much current
should not be

A. sinked from address lines
B. sourced from data lines
C. sinked from data lines
D. sourced or sinked from data lines

Answer 31

D. sourced or sinked from data lines

More current should not be sourced or sinked from data lines while reading to avoid loading

Question 32

Consider the following statements
regarding PLC:
1. It was developed to replace the
microprocessor
2. Wiring between device and relay
contacts are done in its program
3. Its I/0 interface section connects it to
external field devices
4. It requires extensive wiring in the
application

Which of the above statements are
correct?

A. 2 and 4
B. 2 and 3
C. 1 and 3
D. 1 and4

Answer 32

B. 2 and 3

• A Programmable Logic Controller, or
PLC for short, is simply a special computer device used for industrial control systems.

• They are used in many industries such as oil refineries, manufacturing lines, conveyor systems and so on.Where ever there is a need to control devices the PLC provides a flexible way to “softwire” the components together.

• PLCs come in many shapes and
sizes. They can be so small as to fit in your shirt pocket while more involved controls systems require large PLC racks.

• 1/0 - The PLC’s CPU stores and
processes program data, but input and output modules connect the PLC to the rest of the machine; these I/0 modules are what provide information to the
CPU and trigger specific results.

• 1/0 can be either analog or digital;input devices might include sensors,switches, and meters, while outputs might include relay, light, valves and drives. Users can mix and match a PLC’s I/0 in order to get the right configuration for their application.

Option 1 and 4 are wrong because

• PLC does not replace microprocessor
infact it is part of PLC
• It does not require extensive wiring
by PLC.

Question 33

The port that is used for the generation of handshake lines in mode 1 or mode 2 is

A. port A
B. port B
C. port C Lower
D. port C Upper

Answer 33

D. port C Upper

Port C upper is used for the generation of handshake lines in mode 1 or mode 2.

Question 34

The number of memory chips that are
enabled at a time for refresh activity is

A. 2
B. 8
C. 4
D. More than 1

Answer 34

D. More than 1

More than one memory chip can be
enabled at a time to refresh activity to
reduce the number of total memory
refresh cycles.

Question 35

The RAID level 50 is a combination of

A. RAID 1 and RAID 0
B. RAID 3 and RAID 0
C. RAID 5 and RAID 0
D. None of these choices

Answer 35

C. RAID 5 and RAID 0

RAID stands for redundant array of
independent disks. RAID 50, also known
as RAID 5+0, combines distributed
parity (RAID 5) with striping (RAID 0).It requires a minimum of six drives. This RAID level offers better write performance, increased data protection and faster rebuilds than RAID 5.

Question 36

Actuator is the basic component of an
automatic control system.

A. Partly false
B. Partly true
C. False
D. True

Answer 36

D. True

There are 5 basic components of an
automatic control system. They are
error detector, amplifier, actuator, plant,
and sensor. So, Actuator is a basic
component of automatic control
system.

Question 37

If the characteristic equation of the
closed loop system is s^2 + 2s +2=0,
then the system is

A. Over damped
B. Underdamped
C. Undamped
D. Critically damped

Answer 37

B. Underdamped

The given equation is: s^2 + 2s +2=0

It is a second-order differential
equation. The Laplace transform of a
standard form of a second-order
differential equation is

s+2wnos +wn

Comparing the values, we get,
w_n=√2
2w_n8 =2
6=1/√2
6<1
Thus, system is underdamped.

Question 38

The capacitor used which prevents a
portion of the signal from radiating from
their leads.

A. feedthrough
B. neutralization
C. coupling
D. bypass

Answer 38

A. feedthrough

Question 39

Derivative output compensation:

A. Reduction is settling time
B. Improvement in transient response
C. Increase in damping constant
D. Reduction in steady state error

Answer 39

A. Reduction is settling time

Derivative controller is the controller
that is also like high pass filter and is
also phase lead controller and it is used to increase the speed of response of the system by increasing the damping coefficient.

Question 40

A performance index must offer
selectivity.

A. False
B. True
C. Partly true
D. Partly false

Answer 40

B. True

It must offer selectivity, that is, an
optimal adjustment of parameters must
clearly distinguish non optimal
adjustment of parameters. If there was
no selectivity we would not have been
able to distinguish between parameters.

Question 41

Which of the following is not the correct
reason to select feedback
compensation over cascaded one?

A. No amplification is required as the energy
transfer is from higher to lower level.
B. It is economical
C. Suitable devices are not available for
compensation(series)
D. Provides greater stiffness against load
disturbances

Answer 41

B. It is economical

Feedback compensation is the
compensation obtained due to feedback and cascade refers to the cascading of blocks in the forward path and feedback compensation is not preferred over cascading as it is economical.

Question 42

Which of the statement is correct with regard to the bandwidth of the control loop system

A. In systems where the low frequency
magnitude in 0 dB on the bode
diagram, the bandwidth is measured at
the -3 dB frequency
B. The bandwidth is the measurement of the
accuracy of the closed loop system
C. The system with larger bandwidth provides
slower step response and lower fidelity
ramp response
D. The stability is proportional to the
bandwidth

Answer 42

A. In systems where the low frequency
magnitude in 0 dB on the bode
diagram, the bandwidth is measured at
the -3 dB frequency

Bandwidth is the frequency measured at the gain of 3dB and for the good control system the value of the bandwidth must be large but the large value of the bandwidth increases the noise in the
system.