Noise And dB

Question 1

Unit used to express in logarithmic scale the ratio of two values with same dimension

Answer 1

decibel

Question 2

Unit used to quantify gains and losses across telecom system

Answer 2

dB

Question 3

Conversions

Answer 3

PdB = 10log(P2/P1) ; dB

Question 4

dB cannot be converted to ___ reference levels

Answer 4

Any

Question 5

Standard CATV (analog) revd signal

Answer 5

0dBmV

Question 6

Correct conversions

Answer 6

dB-dBm
dBu-dBu
dBf-dBf

Question 7

Does not represent actual amount of power

Answer 7

dB

Question 8

A level of 10dBm refers to:

Answer 8

10dB above 1mW

Question 9

0dB means:

Answer 9

no gain, no loss

Question 10

Operations cant be performed with dB values

Answer 10

Multiplication

Question 11

To which cant a dBm value be converted?
a. dBV
b. dB
c. dBu
d. More than one of the choices

Answer 11

d.

Question 12

10 dBf is equivalent to:

Answer 12

dBf = dBu + 90
dBu = dBf - 90
= 10dBf - 90
-80dBu or -80

Question 13

What is the difference between 25 and -10 dBm?

Answer 13

25dBm - (-10 dBm)
= 35dB

Question 14

What does a power difference of -3dB mean?

Answer 14

A loss of one-half of the power

Question 15

Any unwanted signal tending to interfere with desired signal

Answer 15

Noise

Question 16

Problems
N noise
I interference
D distortion
A attention

Answer 16

Solutions
Filter (1 & 2)
Equalizer
Amplifier

Question 17

Mixing of 2 signals (crosstalk)

Answer 17

Interference

Question 18

Variation of signal shape

Answer 18

Distortion

Question 19

Different freq of diff speed

Answer 19

Delay distortion

Question 20

Signal ampli degradation

Answer 20

Attenuation

Question 21

Signal impairments

Answer 21

Attenuation
Noise
Distortion

Question 22

Categories of Noise

Answer 22

Correlated
Uncorrelated

Question 23

Noise direct result of signal

Answer 23

Correlated

Question 24

Present whether theres a signal or none

Answer 24

Uncorrelated

Question 25

Unwanted cross-product (sum & difference)

Answer 25

Intermodulation

Question 26

Unwanted multiples of single freq

Answer 26

Harmonic distortion

Question 27

Types of Noise

Answer 27

Internal External

Question 28

Any device created by men produce noise Affect freq uo to 500MHz

Answer 28

Man-made or Industrial noise

Question 29

Due to lighting discharge Below 30MHz

Answer 29

Static or atmospheric

Question 30

From stars and galaxies Between 8MHz to 1.43GHz

Answer 30

Extraterrestrial or space noise

Question 31

Solar cycle

Answer 31

11 years

Question 32

Supercycle

Answer 32

99 years

Question 33

Greatly affects satellite comms

Answer 33

Solar noise

Question 34

Noise power formula

Answer 34

N = KTB K= 1.38×10‐²³ B= bandwidth T= temp in kelvin, 273 + °C

Question 35

Noise is essentially

Answer 35

Amplitude variation

Question 36

Noise is a problem in communication system because:

Answer 36

The receive signal are so low in amplitude

Question 37

Industrial freq range ( up to 500MHz)

Answer 37

15 to 120MHz

Question 38

Space noise

Answer 38

8MHz to 1.43GHz

Question 39

Usable microwave freq

Answer 39

1 to 10GHz

Question 40

Sunspot cycle in radio wave propagation occurs every ___ years

Answer 40

11 years

Question 41

A non continuous irregular pulses or noise spikes. Primary source of bit-errors in digital data comms

Answer 41

Impulse noise

Question 42

Low freq noise affects MOS 1/f or flicker or excess noise

Answer 42

Pink noise

Question 43

Burst or popcorn noise Low freq noise affects BJT

Answer 43

Resistance noise

Question 44

Limiting factor in most microwave comms systems such as satellites and radar is ____

Answer 44

Internal noise

Question 45

If resistance is halved, then noise voltage is

Answer 45

Reduced by 29.3%

Question 46

Effect of signal to noise ratio of a system in dB if the bandwidth is halved

Answer 46

Increased by 3dB

Question 47

Noise figure for an amplifier with noise is always

Answer 47

Greater than 1

Question 48

Which noise figure represents the lowest noise? 1.5 dB 2.8 dB 1.2 dBm 4.9 dB

Answer 48

1.5 dB

Question 49

Noise temp is only appropriate to used in circuits or equipment that operates under

Answer 49

VHF UHF Microwave freq

Question 50

What carrier-to-noise ratio is required for microwave relay systems?

Answer 50

10-20dB