# fb-20-est compress

```Excel Review Center
Intensive Final Coaching (IFC)
1.
Calculate the approximate dimensions
for a square patch antenna, for a
frequency of 2 GHz, on a substrate with
a relative permittivity of 2.
A. 50 mm *
B. 40 mm
2.
C. 30 mm
D. 25 mm
A taxi company uses a central
dispatcher, with an antenna at the top of
a 15 m tower, to communicate with
taxicabs. The taxi antennas are on the
roofs of the cars, approximately1.5m
above the ground. Calculate the
maximum communication distance
between the dispatcher and a taxi.
A. 21 km *
B. 10.1 km
3.
C. 12 km
D. 17.3 km
Find the cutoff frequency for the TE10
mode in an air-dielectric waveguide with
an inside cross section of 2 cm by 4 cm.
Over what frequency range is the
dominant mode the only one that will
propagate?
A. 7.0 GHz
B. 15.0 GHz
4.
The GSM cellular radio system uses
GMSK in a 200-kHz channel, with a
channel data rate of 270.833 kb/s.
Calculate the frequency shift between
mark and space.
A.
B.
C.
D.
5.
135.4165 kHz *
153.4615 kHz
315.4165 kHz
351.4615 kHz
system hops to each of 100 frequencies
every ten seconds. How long does it
spend on each frequency?
A.
B.
C.
D.
7.
C. 143 mm *
D. 123 mm
0.01 second per hop
0.1 second per hop *
0.2 second per hop
0.02 second per hop
What length of standard RG-8/U coaxial
cable would be required to obtain a 45&deg;
phase shift at 200 MHz?
A. 124 mm *
B. 125 mm
8.
Find the characteristic impedance of a
coaxial cable using a solid polyethylene
dielectric having ∈r = 2.3, with an inner
conductor 2 mm in diameter and an
outer conductor 8 mm in inside
diameter.
A. 54 8 
B. 84.5 
9.
C. 142 mm
D. 140 mm
*
C. 58.4 
D. 85.4 
Find the maximum dynamic range for a
linear PCM system using 16-bit
quantizing.
C. 89.88 dB
D. 98.08 dB *
10. The North American TDMA digital cell
phone standard transmits at 24.3
kilobaud using DQPSK. What is the
channel data rate?
A.
B.
48.6 kb/s *
45.9 kb/s
C. 46.8 kb/s
D. 44.1 kb/s
11. A three-stage amplifier has stages with
the following specifications. Gain and
noise figure are given as ratios.
Stage
Power
Noise
Gain
Figure
1
10
2
2
25
4
3
30
5
Calculate the equivalent noise
temperature for the whole amplifier.
A. 382 K *
B. 364 K
C. 283 K
D. 285 K
12. Find the modulation index if a 10-volt
carrier is amplitude modulated by three
different frequencies, with amplitudes of
1, 2, and 3 volts respectively.
A. 0.374 *
B. 0.473
C. 0.734
D. 0.300
13. A cell phone transmitter has a maximum
frequency deviation of 12 kHz. Calculate
the modulation index if it operates at
maximum deviation with a voice
frequency of 300 Hz.
A. 45
B. 40 *
A series-tuned circuit operating at a
frequency of 1 GHz is to be constructed
from a shorted section of air-dielectric
coaxial cable. What length should be
used?
A. 133 mm
B. 153 mm
6.
C. 3.5 GHz
D. 7.5 GHz *
A. 90.88 dB
B. 97.98 dB
C. 50
D. 35
14. An FM signal has a frequency deviation
of 5 kHz and a modulating frequency of
1 kHz. The signal-to-noise ratio at the
input to the receiver detector is 20 dB.
Calculate the approximate signal-tonoise ratio at the detector output.
A. 34 dB *
B. 16 dB
C. 43 dB
D. 31 dB
15. A digital communication system uses
sampling at 10 kilo samples per second
(kSa/s). The receiver filters out all
frequencies above 5 kHz. What
frequencies appear at the receiver for a
1 kHz signal frequency at the input to
the transmitter?
A.
B.
C.
D.
1 kHz, 17 kHz and
1 kHz, 13 kHz and
1 kHz, 15 kHz and
1 kHz, 11 kHz and
3 kHz
7 kHz
5 kHz
9 kHz *
16. Calculate the number of levels if the
number of bits per sample is 16 (as
used in the compact disc audio system).
A. 65536 *
B. 66553
C. 63556
D. 63655
17. A signal at the input to a mu-law
compressor is positive, with its voltage
one-half the maximum input voltage.
What proportion of the maximum output
voltage is produced?
A. 0.786Vo
B. 0.876Vo *
C. 0.687Vo
D. 0.781Vo
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18. Convert the 12-bit sample
100110100100 into an 8-bit compressed
code.
A. 11011010 *
B. 01011010
C. 11011011
D. 10011010
19. A radio channel has a bandwidth of 10
kHz and a signal-to-noise ratio of
15 dB. What is the maximum data rate
than can be transmitted using a code
with four possible states?
A. 20 kb/s
B. 40 kb/s *
C. 30 kb/s
D. 50 kb/s
20. A modulator transmits symbols, each of
which has 64 different possible states,
10,000 times per second. Calculate the
baud rate and bit rate.
A.
B.
C.
D.
5 kbaud and 50 kb/s
10 kbaud and 60 kb/s *
20 kbaud and 40 kb/s
15 kbaud and 30 kb/s
21. A carrier with an RMS voltage of 2 V
and a frequency of 1.5 MHz is
modulated by a sine wave with a
frequency of 500 Hz and amplitude of 1
V RMS. Write the equation for the
resulting signal.
A. v(t) = 2.83 + 1.41 sin (3.14 &times; 103t)]
sin (9.42 &times; 106t) V *
B. v(t) = 2.38 + 1.14 sin (3.14 &times; 103t)]
sin (9.42 &times; 106t) V
C. v(t) = 2.83 + 1.41 sin (3.14 &times; 101t)]
sin (9.42 &times; 105t) V
D. v(t) = 2.83 + 1.41 sin (3.14 &times; 102t)]
sin (9.42 &times; 109t) V
22. A modem uses 16 different phase
angles and 4 different amplitudes. How
many bits does it transmit for each
symbol?
A. 2
B. 6 *
C. 4
D. 8
23. A voice transmission occupies a
channel 30 kHz wide. Suppose a
increase its bandwidth to 10 MHz. If the
signal has a total signal power of −110
dBm at the receiver input and the
system noise temperature referred to
the same point is 300 K, calculate the
signal-to-noise ratio for both systems.
A.
B.
C.
D.
19
17
15
13
dB
dB
dB
dB
and -6 dB *
and -9 dB
and -11 dB
and -3 dB
24. A digital communication scheme uses
DQPSK. It is to transmit a compressed
PCM audio signal which has a bit rate of
16 kb/s. The chipping rate is 10 to 1.
Calculate the number of signal changes
(symbols) which must be transmitted
each second.
A. 90 kilobaud
B. 60 kilobaud
C. 80 kilobaud *
D. 70 kilobaud
25. Find the velocity factor and propagation
velocity for a coaxial cable with a Teflon
dielectric (∈r = 2.1).
A. 0.69 and 207 x 106 m/s *
B. 0.69 and 209 x 106 m/s
C. 0.61 and 201 x 106 m/s
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D. 0.63 and 203 x 106 m/s
26. A local loop has a resistance of 1 kΩ,
and the telephone connected to it has
an off-hook resistance of 200 Ω.
Calculate the loop current and the
voltage across the telephone when the
phone is on hook.
A.
B.
C.
D.
zero and full battery voltage *
infinite and zero voltage
10 A and -48 V
5 A and -48 V
27. An FM signal has a deviation of 3 kHz
and a modulating frequency of 1 kHz. Its
total power is 5 W, developed across a
50 Ω resistive load. The carrier
frequency is 160 MHz. Calculate the
RMS signal voltage.
A. 18.5 V
B. 20.1 V
C. 15.8 V *
D. 21.6 V
28. A 50-Ω line is terminated in a 25-Ω
resistance. Find the SWR.
A. 1
B. 0.5
C. 2 *
D. 0
29. What frequencies are generated by a
telephone using DTMF signalling when
the number 9 is pressed?
A.
B.
C.
D.
852 Hz and
697 Hz and
941 Hz and
770 Hz and
1477 Hz *
1477 Hz
1477 Hz
1477 Hz
30. Find the propagation loss for a signal at
800 MHz, with a transmitting antenna
height of 30 m, over a distance of 10
km, using the free-space model.
A. 110.5 dB *
B. 124.1 dB
C. 115.0 dB
D. 121.3 dB
31. An open-wire line uses wire with a
diameter of 2 mm. What should the wire
spacing be for an impedance of 150 Ω?
A. 1.5 mm
B. 3.5 mm *
C. 2.5 mm
D. 4.5 mm
32. A resistor has a noise temperature of
300 K. Find its noise power density.
A.
B.
C.
D.
4.14 &times;
4.14 &times;
4.14 &times;
4.14 &times;
10−19 W/Hz
10−23 W/Hz
10−21 W/Hz *
10−18 W/Hz
33. A generator sends 50 mW down a 50-Ω
line. The generator is matched to the
line but the load is not. If the coefficient
of reflection is 0.5, how much power is
reflected and how much is dissipated in
A.
B.
C.
D.
12.5 mW
15.0 mW
25.1 mW
10.5 mW
and 37.5
and 35.5
and 56.1
and 35.5
mW *
mW
mW
mW
34. A transmitter supplies 50 W to a load
through a line with an SWR of 2. Find
the power absorbed by the load.
A. 44.4 W *
B. 34.4 W
C. 54.3 W
D. 64.4 W
35. A transmission line is specified to have
a loss of 4 dB/100 m at 800 MHz. Find
the loss in decibels of 130 m of this
cable.
A. 3.2 dB
B. 5.2 dB *
C. 1.2 dB
D. 2.2 dB
36. A waveguide has a cutoff frequency for
the dominant mode of 10 GHz. Two
signals with frequencies of 12 and 17
GHz respectively propagate down a 50
m length of the guide. Calculate the
difference in arrival time for the two.
A. 95.5 s
B. 95.5 ns *
C. 95.5 ms
D. 95.5 ps
37. A power of 100W is supplied to an
isotropic radiator. What is the power
density at a point 10 km away?
A. 79.6 nW/m2 *
B. 97.1 nW/m2
C. 76.9 nW/m2
D. 87.1 nW/m2
38. A transmitter has a power output of
150W at a carrier frequency of 325MHz.
It is connected to an antenna with a gain
of 12 dBi. The receiving antenna is
10 km away and has a gain of 5 dBi.
Calculate the power delivered to the
propagation. Assume also that there are
no losses or mismatches in the system.
A. -33.9 dBm *
B. -43.3 dBm
C. -39.3 dBm
D. -53.5 dBm
39. Find the propagation loss for a signal at
800 MHz, with a transmitting antenna
height of 30 m, over a distance of 10
km, using the mobile-propagation
model.
A. 159.5 dB *
B. 165.0 dB
C. 195.5 dB
D. 175.1 dB
40. An AM transmitter has a carrier power
output of 50W.What would be the total
power produced with 80% modulation?
A. 56 W
B. 46 W
C. 66 W *
D. 76 W
41. An automobile travels at 60 km/hr. Find
the time between fades if the car uses a
cell phone at 800 MHz.
A. 12.1 ms
B. 11.2 ms *
C. 10.1 ms
D. 14.3 ms
42. A metropolitan area of 1000 square km
is to be covered by cells with a radius of
2 km. How many cell sites would be
required, assuming hexagonal cells?
A. 83
B. 73 *
C. 93
D. 63
FB 20 - EST
A. 60 mm
B. 70 mm
C. 80 mm *
D. 90 mm
45. A pyramidal horn has an aperture
(opening) of 58 mm in the E plane and
78 mm in the H plane. It operates at 10
GHz. Calculate its gain in dBi.
A. 15.8 dBi *
B. 13.9 dBi
C. 18.5 dBi
D. 12.9 dBi
46. A resistor at a temperature of 25&deg;C is
connected across the input of an
amplifier with a bandwidth of 50 kHz.
How much noise does the resistor
supply to the input of the amplifier?
A. 0.206 fW * *
B. 0.206 W
C. 0.206 pW
D. 0.206 aW
47. Citizens’ band radio channels are 10
kHz wide. What is the maximum
modulation frequency that can be used
if a signal is to remain entirely within its
assigned channel?
A. 5 kHz *
B. 3 kHz
C. 10 kHz
D. 15 kHz
48. Calculate the minimum data rate
needed to transmit audio with a
sampling rate of 40 kHz and 14 bits per
sample.
A. 460 kb/s
B. 640 kb/s
C. 560 kb/s *
D. 650 kb/s
49. A signal would have a bandwidth of 200
kHz and a signal-to-noise ratio of 20 dB
if transmitted without spreading. It is
spread using a chipping rate of 50:1.
Calculate its bandwidth and signal-tonoise ratio after spreading.
A.
B.
C.
D.
10 MHz and 3 dB *
5 MHz and 1.5 dB
7.5 MHz and 7 dB
1 MHz and 3.5 dB
50. A transmitter has a power output of 10
W at a frequency of 250 MHz. It is
connected by 20 m of a transmission
line having a loss of 3 dB/100 m to an
antenna with a gain of 6 dBi. The
receiving antenna is 25 km away and
has a gain of 4 dBi. There is negligible
loss in the receiver feedline, but the
and line are designed for a 50 Ω
impedance, but the receiver input is 75
Ω. Calculate the power delivered to the
propagation.
A. -51.9 dBm
B. -61.9 dBm
C. -59.1 dBm *
D. -69.1 dBm
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43. Calculate the free-space path loss at a
frequency of 1 GHz, for each of the
following paths, to a point on the earth
directly under the satellite from a LEO
satellite at an altitude of 500 km.
A. 164.1 dB
B. 143.3 dB
C. 146.4 dB *
D. 145.2 dB
44. A helical antenna with 8 turns is to be
constructed for a frequency of 1.2 GHz.
Calculate the optimum diameter.
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```