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90 Cards in this Set

  • Front
  • Back
cw transmitter requires four essential components.
generates the rf carrier at a preset frequency and maintains it within close tolerances
is a voltage amplifier that increases the amplitude of the oscillator signal to a level that drives the power amplifier (pa).
intermediate power amplifier stage (referred to as the ipa)
buffer serves two other purposes?
isolate the oscillator from the amplifier stages.
frequency multiplier.
final stage of a transmitter is the
power amplifier
instantaneous amplitude of the rf output signal is varied in proportion to the
modulating signal.
converts the audio frequency (af) input (a person’s voice) into corresponding electrical
amplifies the audio, and the modulator further amplifies the audio signal to the amplitude necessary to fully modulate the carrier
combines the rf carrier and the modulating signal in the power amplifier to produce the
amplitude-modulated signal output for transmission
In the absence of a modulating signal
a continuous rf carrier is radiated by the antenna.
the modulating signal combines with the carrier to cause the frequency
of the resultant wave to vary with the instantaneous amplitude of the modulating signal
frequency modulation
With no modulation in FM the
oscillator generates a steady center frequency
The modulating signal applied to a varicap causes
the reactance to vary
increase the frequency and then to a power amplifier to increase the amplitude to the desired level for transmission
frequency multiplier
are always exact multiples of the basic or fundamental frequency generated by an
oscillator and are created in amplifiers and their associated circuits
True harmonics
Designing and building a stable crystal oscillator is difficultget around
this problem by operating the oscillators in most transmitters at what comparatively frequencies
main difference between low-frequency and high-frequency transmitters is the
number of frequency-multiplying stages used.
is the elimination of the undesired portions of the signal
combines its audio input and its carrier input to produce the two sidebands.
ssb generator (modulator)
two sidebands are then fed to a what that selects the desired sideband and suppresses the other one.
By eliminating the carrier and one of the sidebands, intelligence is transmitted at a savings in?
power and frequency bandwidth
uses ssb as a means of
communications between fleet commanders; and fleet commanders use it for communications between
their subordinates and adjacent commands.
high command (HICOM) network
uses outputs from two sideband generators; it suppresses both carriers and then filters out an upper
sideband from one and a lower sideband from the other. We then combine the two remaining sidebands
and transmit an envelope with upper and lower sidebands that contain different intelligence
Independent sideband (isb)
a method for simultaneous transmission of two or more signals over a common carrier wave
for operator-to-operator service messages and for making frequency changes
when necessary
occurs when a transmitted electromagnetic wave passes through the receiver antenna and
induces a voltage in the antenna.
is the ability of the receiver to select a particular frequency of a station from all other
station frequencies appearing at the antenna of the receiver.
is the action of separating the low (audio) frequency intelligence from the high (radio) frequency carrier. A detector circuit is used to accomplish this action.
is the action of converting the electrical signals to sound waves, which can then be interpreted by your ear as speech, music, and the like
The ability of a receiver to reproduce weak signals is a function of the of a receiver
is the limiting factor of sensitivity.
of a receiver is its ability to accurately reproduce, in its output, the signal that appears at
its input
is the process used to tune two or more circuits with a single control.
Ganged tuning
There is a fixed difference in frequency between
the local oscillator and the rf amplifier at all times. This difference in frequency is the
A typical value of IF for an AM communications receiver is
455 kilohertz
is a circuit designed to
respond to frequency shift variations
which limits all signals to the same amplitude level to minimize noise interference
LIMITER circuit
What frequency conversion principle is used to develop the IF?
What is the major disadvantage of an fm signal as compared to an AM signal?
Wide bandpass
What two components give a ssb receiver its advantages over an AM superheterodyne receiver?
special type of detector and a carrier reinsertion oscillator
What does manual gain control do to strong and weak signals, respectively?
Attenuates the strong and amplifies the weak.
What is the purpose of agc/avc in a receiver?
To limit unwanted variations in the output.
What is a disadvantage of agc?
Weak signals produce bias, which could result in no usable receiver output.
What is the main difference between agc and dagc?
Dagc does not attenuate weak signals.
What is the function of the bfo?
It is heterodyned with the rf to produce an audio frequency.
What is the purpose of a squelch circuit?
It eliminates noise when no signal is being received.
What does a tone control circuit in a receiver do to the audio signal?
It controls the amount of bass and treble response
What is the function of a crystal filter in a receiver?
It is used to achieve maximum selectivity.
What is the primary function of an afc circuit?
It is used to accurately control the frequency of the oscillator
What is frequency synthesis?
The process of selecting and/or heterodyning frequencies to produce a signal frequency
is when an amplifier is driven toward cutoff.
What are the basic functions of a handset?
To convert energy electrical/acoustic to acoustic/electrical and to key/unkey a transmitter. Also it mutes a receiver when transmitting.
What capability does a transmitter transfer switchboard provide?
Transferring remote control functions and signals to transmitters
What function does a receiver transfer switchboard perform?
Transfers receiver audio outputs to remote control stations.
If the rf amplifier discussed has an 80 milliwatt input, what would be the maximum output?
800 watts.
What are the tuning modes for the coupler group discussed?
Automatic, semiautomatic, and manual.
What is the purpose of an antenna coupler?
It matches the impedance of an antenna to that of a transmission line at any desired frequency.
Why is the coupler pressurized with nitrogen?
To aid in heat transfer and prevent corona and arcing.
What are the transmitter operating modes?
Lsb, usb, isb, AM, cw, fsk.
What type of tuning does the receiver use?
What is the function of an antenna patch panel?
To connect an antenna/transmission line to a receiver/transmitter.
What are the functions of a multicoupler?
Patching and filtering and permits the multiple use of receivers and/or transmitters on a single
What are the terms used to describe an open or closed telegraph circuit?
Space and mark.
How many units are in a tty signal and what are they?
Intelligence (5), start (1), stop (1).
There are not enough combinations of the five-unit code to handle the alphabet, symbols and so forth. What is used to increase the number of available code combinations?
Shift signals.
What are the two teletypewriter modes of operation?
Synchronous and nonsynchronous.
Define baud.
A unit of modulation rate.
Define bit.
Binary digit.
What are the two types of dc operations used to represent mark and space conditions?
Neutral and polar.
What is the function of a keyer?
Converts dc to corresponding mark and space modulation
What is the function of a converter?
Converts the audio signal to dc pulses.
Basically describe an afts system.
Uses AM to change dc to audio.
Basically describe an rfcs system.
A keyer provides rf excitation, which can be shifted above or below the assigned frequency.
Most Navy tty sets operate at what speeds?
60, 75, or 100 wpm.
A receive tty set provides outputs in what formats?
Page-size copy paper and perforated tape.
What does the color red indicate on a tty patch panel?
It handles classified information.
What are the functions of cryptographic equipment?
To code or decode messages
What are the functions of a converter-comparator group?
The comparator compares the signal strengths from the receivers and the converter converts the frequency-shift rf signal into a tty set dc loop control signal.
What is the function of a tone terminal set?
It converts dc to audio or vice versa
What are the two types of multiplexing?
Time-division and frequency-division
What is the purpose of multiplexing?
It allows simultaneous transmission of multiple signals on a single transmission path.
The transmission of still images over an electrical communications system is known as what?
The term TEMPEST refers to what?
Compromising emanations.
What are the three fundamental requirements of a military communications system?
Reliability, security, and speed.
Which of the above requirements is most important?
What is the purpose of QMCS?
To ensure continuous, optimum performance of communications systems.
What is emi?
Electromagnetic interference.
What are the two emi transmission methods?
Conduction and radiation.
Electromagnetic radiation is hazardous to personnel in what two ways?
Rf burns and biological, thermal, and neurological effects.
What is the most useful and widespread technique to reduce rf burn hazards?
Proper bonding and grounding