Sample Exam 4 – Radio Society of Sri Lanka

Fundamentals of Electricity & Radio Communications sample paper-4

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The Radio Society of Sri Lanka

The copy right of the information contained in this sample exam are with the Radio Society of Sri Lanka (RSSL).

These questions are mainly targeting the Radio Amateur exam for Novice and General class. The recommended time duration is 1 hour. For more information please contact Mr. Jayasiri Wijeratne (4S7VJ) 4s7vj@rssl.lk

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Congratulations - you have completed Fundamentals of Electricity & Radio Communications sample paper-4. You scored %%SCORE%% out of %%TOTAL%%. Your performance has been rated as %%RATING%%

Your answers are highlighted below.

Question 1

29.1MHz is the third harmonic of

A	19.4 MHz
B	87.3 MHz
C	9.7 MHz
D	90 MHz

Question 2

What happens to the input impedance of a Yagi antenna when more elements are added ?

A	increases
B	remains unchanged
C	Decreases
D	will cause unbalanced

Question 3

An antenna whose input impedance is 50Ω Should have a feeder link with an impedance of

A	50 Ω
B	100 Ω
C	300 Ω
D	75 Ω

Question 4

The automatic gain control (AGC) circuit is usually used to control the gain of the

A	IF amplifier
B	mixer
C	detector
D	audio amplifier

Question 5

The Radiation Resistance of a ½-wave dipole is

A	300 Ohms
B	75 Ohms
C	100 Ohms
D	50 Ohms

Question 6

What is the effective capacitance between the points A and B shown in the diagram ?

A	9pF
B	18 pF
C	27 pF
D	1 pF

Question 7

A sunspot cycle is

A	21 years
B	10 years
C	11 years
D	5 years

Question 8

The total power content of an amplitude modulated signal is 10W, and the percentage modulation is 100%. The power transmitted by the side bands is

A	6.67 W
B	10 W
C	5 W
D	3.33 W

Question 9

A fuse is used in an electrical circuit

A	to prevent damage of all equipment due to overload
B	to prevent AC hum
C	none of these
D	to protect from lightning

Question 10

Radio waves above 30 kHz are called

A	Audio frequencies.
B	super high frequencies
C	radio frequencies.
D	very high frequencies.

Question 11

A 300 Ohm twin feeder line is

A	a wave guide
B	an unbalanced line
C	none of the above
D	a balanced line

Question 12

If a person gets an electric shock you should immediately

A	Give him artificial respiration
B	Remove the victim to a safe place
C	Send for a doctor
D	Switch off the mains supply immediately

Question 13

A dipole is used on 7 MHz will work very efficiently on

A	3.5 MHz
B	14 MHz
C	21 MHz
D	28 MHz

Question 14

A transformer is laminated to

A	reduce eddy current losses
B	increase exciting current
C	reduce hysteresis losses
D	increase magnetic flux

Question 15

Which one is incorrect from following statments

A	Power factor of a capacitor is infinity
B	Power factor = actual power / apperent power
C	Power factor of a pure resistor is 1
D	Power factor of a pure inductor is zero

Question 16

The equivalent resistance of the circuit given is

A	22 kΩ
B	1 kΩ
C	11 kΩ
D	10 kΩ

Question 17

The conductivity of a current carrying conductor can be decreased by

A	reducing its diameter
B	reducing its length
C	increasing its diameter
D	reducing its temperature

Question 18

The ability of a receiver to pickup weak signal is

A	none of these
B	sensitivity
C	selectivity
D	stability

Question 19

The basic concept of Amplitude Modulation (AM) is to vary the

A	amplitude of carrier signal
B	frequency of carrier signal
C	amplitude of modulating signal
D	frequency of modulating signal

Question 20

The unit of electric current is

A	Ampere hour
B	Hertz
C	Ampere
D	Volt

Question 21

The value of the resistor shown in the figure is

A	12Ω
B	210Ω
C	120Ω
D	21Ω

Question 22

The resonance frequency of a tuned (LRC) series circuit is given by

A	(1 / 2π)√(L/C)
B	2π/√(LC)
C	1 / 2π√(LC)
D	1 / [2π√(LC)]

Question 22 Explanation:

The correct answer is 1 / [2π√(LC)] ; but 1 / 2π√(LC) is confused whether it is equal to 1 / [2π√(LC)] or [1 / 2] π√(LC)

Question 23

The electric field of an antenna is parallel to the Earth’s surface. The polarization of the antenna is

A	none of these
B	circular
C	horizontal
D	vertical

Question 24

How can key clicks be eliminated?

A	Neutralize the P.A.
B	Use a key click filter
C	Have an antenna matching device.
D	Should have a regulated power supply

Question 25

Envelope of diode detector is used for the detection of

A	AM signals
B	SSB signals
C	FM signals
D	CW signals

Question 26

20 dB power gain is an increase power by

A	20 times
B	10 times
C	2 times
D	100 times

Question 27

What is the total inductance between A and B ?

A	9 mH
B	27 mH
C	18 mH
D	1 mH

Question 28

To determine the voltage polarity across a resistor, we should know

A	the magnitude of the current
B	the direction of the current
C	the value of the resistor
D	the battery voltage

Question 29

A moving coil meter responds only by itself to

A	AC+DC
B	DC
C	AC
D	Frequency

Question 30

The deviation of a standard 2 meter Amateur Radio Transmitter is

A	5kHz
B	2.5 kHz
C	50 kHz
D	25 kHz

Question 31

A vertical polarized transmission could have for best reception

A	a cross polarized antenna
B	A horizontal receiving antenna
C	a circular polarized antenna
D	a vertical receiving antenna

Question 32

A 10 Ohm resistor consumes a current of 1 Ampere. The power dissipated in the resistor is

A	1 Watt
B	0.1 Watt
C	100 Watts
D	10 Watts

Question 33

A coaxial cable is

A	none of these
B	a wave guide
C	a balanced line
D	an unbalanced line

Question 34

The Meggar is used for

A	measuring current
B	measuring voltage
C	testing insulation
D	measuring power

Question 35

The purpose of adding reflector and directors to a folded dipole antenna is

A	to decrease its impedance
B	to have some effect on its impedance
C	none of these
D	to increase its impedance

Question 36

Over modulation in an F.M. transmission will cause

A	To occupy narrow bandwidth
B	none of the above
C	to occupy wide bandwidth
D	Heavy distortion

Question 37

One way communication is called

A	half duplex
B	duplex
C	simplex
D	monocom

Question 38

The transformer is used to change the value of

A	frequency
B	power
C	none of these
D	voltage

Question 39

The power input of a transistor is

A	collector current X collector voltage
B	base current X collector voltage
C	Emitter current x base current
D	collector current X emitter current

Question 40

An R.F. choke

A	prevent AC ripple.
B	Aids the flow of R.F. current
C	prevent the flow of R.F. current
D	accelerates the flow of R.F.

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