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The first complete system of wireless communications was provided by
Guglielmo Marconi
An intricate part of electronic communications system because of its up- and down-conversion functions as they are transported through a channel
translation
In radio communication, the difference between the output power of the transmitter to the minimum required power of the receiver is
system gain
The frequency band normally used to penetrate ocean depths and therefore used for communicating with submarine
ELF
The frequency band used as subcarriers or signals which carry the baseband modulating information but in turn modulate another higher-frequency carrier
LF
In what major RF band is ground wave basically applied
MF
These are frequencies generally known as short waves
HF
These are frequencies used in two-way or amateur radio CB communications
HF
Line of sight communications is not a factor in which frequency range
HF
The frequency band used by cellular telephones and mobile communication services is
UHF
Troposheric scatter is used with which frequencies
UHF
VLF waves are for some types of services because
they are very reliable
Medium frequency range is also
hectometric wave
Super High frequency is also
centimetric
The amplitude of a sine wave which is modulated by a musical program will
be complex and contain fundamental and harmonic frequencies
A type of noise caused by random arrival of carriers at the output element of an active electronic device
transistor noise
Industrial noise frequency is between
15 to 160 MHz
Standard design reference for environmental noise temperature in degrees centigrade
17C or 290K
Audio signals are not propagated directly to space because
they will require antennas that are too long
Which of the following circuits is immediately fed into the discriminator on a frequency modulation receiver
local oscillator
Oscillators that are not self-sustaining are called
triggered
A circuit that compensates for minor variations in the received RF signal level
automatic gain control
In microwave communications system, the minimum radio fading that maybe compensated by the AGC is
40 dB
In microwave communications, for proper operation, a magnetron must be accompanied by a
permanent magnet
It is the point where the reflected resistance is equal to primary resistance and the Q of the primary tank circuit is halved and the bandwidth doubled
critical coupling
Which of the following emission (AM) is used as that when the modulation index is doubled, the antenna current is also doubled
J3E
What type of emission is produced when an amplitude modulated transmitter is modulated by a fax signal
A3C
Phase modulation emission type
G3E
Frequency tolerance for the RF carrier in the standard AM radio broadcast band
+/- 20 Hz
FM broadcast frequency tolerance
+/- 2 kHz
Standard FM bandwidth
200 kHz
What is the channel width of an AM station
10 kHz
It is a form of amplitude modulation in which the carrier and one complete sideband is transmitted, but only part of the second sideband is transmitted
VSB or vestigial sideband
Which component is used to produce AM at very high frequencies
PIN Diode
To provide two or more voice circuits with the same carrier, what system must be used
ISM emission
What is the advantage of series modulation
high gain selectivity
In the spectrum of a frequency-modulated wave, __
total number of sidebands depends on the modulation index
What is the modulation used for stereophonic subcarrier of FM composite baseband signal
AM DSBSC
Frequency deviation of standard FM broadcast
75 kHz
Deviation ratio for commercial FM
5
FM broadcast guard band
+/- 25 kHz
In a stereophonic FM, SCA has a carrier of
67 kHz
Pilot subcarrier frequency used in FM stereophonic transmission
19 kHz
THe L-R stereo channel in FM broadcasting is between
23 kHz to 53 kHz
What is the radio transmission of two separate signals, left and right, used to create a multidimensional effect on the receiver
Stereo system
In an FM stereo multiplex transmission, __
the difference signal modulates the 38-kHz subcarrier
A monoaural FM receiver receives only the ___ signal of the stereo multiplex transmission
L+R
Where is the pre-emphasis added in a stereo FM
before the matrix at the transmitter
Where is the de-emphasis added in a stereo FM
after the matrix at the receiver
An additional channel of multiplex information that is authorized by the FCC for stereo FM radio stations to feed services such as commercial free programming to selected customers
SCA or subsidiary communications authority
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