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114 (8th WK) Flashcards

1
Q

indicate the false statement the superheterodyne receiver replaced the TRF receiver because the latter
suffered from

A

Inadequate selectivity at high frequencies

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2
Q

It is true that digital system where the signal is transmitted and received in digital form.

A

Digital communication System

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3
Q

A standard AM wave has a total transmitted power of 4 kW Modulated 85%. How much total power should an SSB wave contain in order to have the same power content as that contained in the two sidebands?

A

2123W > (or 3.4kW?)

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4
Q

A PCM system has the following parameters: a minimum sampling rate of 10 KHz, a maximum decoded voltage at the receiver of +_5V, and a minimum dynamic range of 80dB. Determine the maximum analog input that will not result to aliasing (in Hz)

A

5000

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5
Q

Compute for the free space path loss in dB for a 400MHz at 40 Km away from the source.

A

116

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6
Q

Which of the following is not an application under VHF

A

Upper TV channels 14-83

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7
Q

In an FM signal, the signal power __as the modulation index increase.

A

Remains constant

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8
Q

What Is the meaning of the velocity factor of a transmission line?

A

The velocity of the waves on the transmission line is divided by the velocity of light in a vacuum.

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9
Q

Function of a data link protocol that coordinates hop-to-hop data delivery where a hop maybe a computer, a network controller or a network connecting device such as router.

A

Flow control

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10
Q

Indicate in which of the following only one sideband is transmitted:

A

H3E

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11
Q

In a message, 2 of the characters are in error. The 1st character has a single error on b2 while the 2nd character has two errors; one error is in b1 and the other at b5. Which of the following statements is correct

A

The error on the 1st character can be detected by VRC and LRC. The error on the 2nd character can be detected by LRC but not by VRC.

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12
Q

What is mean by antenna gain?

A

The ratio of the amount of power produced by the antenna compared to the output power of the transmitter

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13
Q

Determine the check digit: 978-971-778-195-x

A

2

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14
Q

In FSK, if the mark frequency is equal to 28Khz and the space frequency is 20KHz, what is the carrier in frequency in KHz?

A

f_c = (f_m + f_s) / 2
f_c = (28 kHz + 20 kHz) / 2
f_c = (48 kHz) / 2

ANS: 24

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15
Q

A mixer stage has a noise figure of 25dB, and this is preceded by an amplifier that has a noise figure of 10 dB and an available power gain of 20 dB. Determine the overall noise figure referred to the input

A

20.0012 > 11.19?

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16
Q

If the bit interval of a digital input is equal to1000μs, what is the baud rate if the system is using QPSK?

A

500

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17
Q

What is the product of the power supplied to the antenna and its gain relative to the half wave dipole in a given direction?

A

Effective radiated power

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18
Q

Which of the following statements is true about fiber optic cable?

A

Its core must be more dense than the clad

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19
Q

Compute for the guardband in between channels in a master group with 2.5Mhz total bandwidth

A

200.33

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20
Q

Which of the following frequency bands does sky wave propagation usually apply?

A

HF band

3 - 30 MHZ (EST)

21
Q

A superheterodyne receiver with an IF of 450 kHz tuned to a signal at 1200 kHz. What is the local oscillator frequency needed produce an IF of 450KHz

A

2100Hz > 750hz?

22
Q

A web client is receiving a response for a web page from a web server. From the perspective of the client, what is the correct order of the protocol stack that is used to decode the received transmission?

A

Ethernet, IP, TCP, HTTP

23
Q

What is the equivalent noise resistance ( in ohms) when the measured noise voltage is 500x10^-15V. the temperature is 20C and the bandwidth is 5kHz?

A

0.00000000309

24
Q

What type of network traffic requires QoS

A

Video conferencing

25
Q

Consider the analog signal x(t) = 3cos(500πt). What is the minimum sampling rate required to avoid aliasing?

A

250 > 1000Hz?

26
Q

A frequency modulated signal which is modulated by a 3-kHz sine wave reaches the maximum frequency of 100.02 MHz and minimum frequency of 99.98 MHz. what is the modulation index of the signal?

A

13.33

27
Q

Determine the coding efficiency required for the dynamic range: 100dB. Use 2 decimal places

A

97.83

28
Q

What term describes a technology that allows devices to connect to the LAN using an electrical outlet?

A

Powerline networking

29
Q

Intermediate frequency for an AM broadcasting system as per FCC rules.

A

455kHz

30
Q

It is the measure of the mismatch between a load and the transmission line.

A

Reflection coefficient

31
Q

A waveguide is considered as _____.

A

High pass filter

32
Q

A 50-W resistor operates at room temperature (25C). How much noise power (in femtoWatts) does it provide to a matched load over the bandwidth of A TV channel of 6MHz.

A

24.698 > 0.002483167 or 2.47 *

N = k * T * B

33
Q

A type of transmission line whose conductors experience the same electrical capacitance relative to the ground

A

Balanced

34
Q

What are two services provided by the OSI network layer?

A

Routing packets toward the destination

35
Q

A dipole antenna requires to be fed with 20 kW of power to produce a given signal strength to a particular distant point. If the addition of a reflector make s the same field strength with and input power of 11kW. What is the dB gain obtained by the use of the reflector?

A

2.6 dB
(Pinoy Bix)

36
Q

The signal level at the input of the amplifier is 120 mV, and the noise level is 6 mV. Calculate the noise figure of the amplifier if the signal to noise ratio at output is 20 dB

A

6.02

37
Q

A computer can access devices on the same network but cannot access devices on other networks. What is the probable cause of this problem?

A

The computer has an invalid default gateway address.

38
Q

An electromagnetic wave is ____ polarized when the electric field lies in a plane parallel to the earth’s surface

A

Horizontal

39
Q

A 4 kHz audio signal modulates a 125 MHz carrier, causing a frequency deviation of 5kHz. The bandwidth of the narrow band FM signal is ___ kHz

A

8 > 18 or 9

40
Q

What causes fold-over distortion?

A

Is produced by getting not enough samples from the analog input

41
Q

All energy signals will have an average power of _________

A

Zero

42
Q

An open-circuited transmission line with a length greater than wavelength λ/4 but less than λ /2 will exhibit ____ reactance

A

Inductive

43
Q

For a given length of RG 8A/U coaxial cable with a distributed capacitance C=96.6 pF/m, a distributed inductance L=241.56nH/m, determine the velocity of propagation

A

2.07 x 10^8 m/s

44
Q

What process involves placing one PDU inside of another PDU?

A

Encapsulation

45
Q

network is made of a set of switches connected by physical links, in which each link is divided into n channels.

A

circuit-switched

46
Q

What important information is examined in the Ethernet frame header by a Layer 2 device in order to forward the data onward?

A

destination MAC address

47
Q

What layer is responsible for routing messages through an internetwork in the TCP/IP model?

A

Internet

48
Q

Which is not true about synchronous time-division multiplexing?

A

In synchronous TDM, the multiplexer combines light signals using a fiber channel and produces unidirectional light.

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