M2 B2 Flashcards
Which US government agency divides the radio frequency spectrum into different bands?
Federal Communications Commission (FCC)
High-frequency (HF) transmissions are normally conducted in which two operating modes?
SSB and ISB
Which frequency band is most susceptible to jamming?
High frequency (HF)
The ability of a receiver to reproduce the signal of a very weak station is characteristic of a receiver’s
sensitivity
The ability of a receiver to reproduce the input signal accurately is characteristic of its
fidelity
A combination transmitter and receiver, built as a single unit and shares common tuned circuits, is called a
transceiver
Conductor material resistance in a transmission line leads to this type of loss
Copper loss
The amount of skin-effect loss is directly proportional to the
frequency
Leakage loss in a transmission line is minimized by using a
very high-resistance dielectric
A transmission line that consists of a center conductor, placed inside a rigid metal tube that functions as the outer shield, is called
rigid coaxial cable
A waveguide is a type of transmission line that you would use
when the frequencies are so high that their wavelength is miniscule
All statements concerning waveguides are true except
their outer surface will arc from being very slightly damaged
Which two transmission line properties determine its characteristic impedance (ZO)?
Inductance and capacitance
This is the correct statement concerning a wavelength
Wavelength is inversely related to frequency.
Determine the wavelength of a 250 megahertz (MHz) signal
1.2 meters
A nonresonant transmission line is one with
no reflected waves
When discussing resonant and nonresonant transmission lines
maximum power transfer results from a nonresonant line
This will likely result if a transmission line is terminated in an open
Signal loss would be significant
Direct waves are radio waves that travel
through the air in a straight line from transmitter to receiver
Radio waves that travel near the Earth’s surface are called
ground waves
The Earth’s conductivity is determined by the type of
soil and water in the propagation path
This term is used to describe radio waves that bend as they travel from one medium to another that has different density
Refraction
The refractive index of air depends on moisture
atmospheric pressure, and temperature
When comparing the radio and optical horizons, which one is farther away and by what percentage?
Radio, 15
Which process permits communication in shadow regions behind obstacles?
Diffraction
Which frequency range will show little effect from precipitation?
High frequency (HF)
Line-of-sight (LOS) radio waves that are guided through the air between two layers of the atmosphere are known as
ducting
Which condition gives sky-wave propagation its ability to communicate beyond the optical line-of-sight (LOS)?
Refraction
The angle at which a radio wave enters the ionosphere is known as the
angle of incidence
There are several critical sky-wave propagation angles and frequencies. Radio waves that angle too low are
absorbed before refraction occurs
In sky-wave propagation, frequencies higher than the critical frequency are
passed into space
The term frequency of optimum transmission (FOT) is also referred to as the
optimum traffic frequency
In sky- and ground-wave propagation, the area of silence where no signals are received is known as the
skip zone
This occurs when a transmitted signal travels over two or more separate paths during transmission
Multipathing
How many layers make up the Earth’s atmosphere?
5
This occurs when high-energy ultraviolet light waves from the sun enter the ionospheric region of the atmosphere and strike the gas atoms
Ionization
The atmospheric recombination process is dependent on the
time of day (TOD)
Which layer of the ionosphere is most important for high-frequency (HF) communications?
F
During which season do we have the wider range of critical frequencies and less absorption of all frequencies?
Winter
As ionospheric solar variations, sunspots are disturbances that appear and disappear
on the sun’s surface
On which regular ionospheric variation do sunspots occur?
11-year cycle
In a basic communication system, this is used to convert radio frequency (RF) current oscillation into electric and magnetic fields of force.
Antenna
The concept where alternating current (AC) changes in magnitude, and reverses its direction during each cycle, is
what makes radio transmission possible
At which point do magnetic fields around a wire no longer have time to collapse completely between alternations?
10,000 cps
In radio-wave creation, which type of field detaches from the antenna and travels through space at great distances?
Radiation
Which types of polarization do most satellite communication terminals transmit and receive?
Transmit right-hand circular and receive left-hand circular polarizations
A resonant antenna effectively radiates a radio signal for frequencies close to its designed frequency. Which percentage range, plus or minus, is it usually within?
2
The design frequency of a resonant antenna is 10 megahertz (MHz). What will be its frequency range?
9.8 - 10.2 MHz
The lowest frequency at which an antenna resonates is known as its
fundamental
The ability of an antenna to both receive and transmit equally well is known as the antenna’s
reciprocity
This matching device is inserted to make a transmitter “think” it is connected to a low standing-wave ratio (SWR) antenna
Coupler
This matching device would be used to connect a 52-ohms RG–213 cable to an antenna with an impedance of 600-ohms
Balun
Which type of antenna radiates radio energy equally well in all directions?
Omni-directional
Add this device to make a long-wire antenna more directional
Terminating resistor
Beam width of a directive antenna is measured at the
half-power point
A dipole or long-wire antenna is an example of a
Hertz antenna
This is one of the simplest and most functional antennas in use
Half-wave dipole
The minimum length of a long-wire antenna is
one wavelength
You should use this type of antenna to communicate over the horizon to an amphibious ship on the move or to a station up to 450 kilometers away
Near-vertical incidence sky-wave
How are most antennas designed that are used in satellite communications?
Directional
Which type of polarization is used to radiate a signal using a helical satellite antenna?
Cicular
This type of antenna is used to transmit and receive microwave signals
Horn
Where are aircraft antennas normally housed?
Inside NONCONDUCTIVE radomes outside or flush with the fuselage.
At which vertical angles should the multi-hop, long-distance transmission be used in airborne antenna applications for frequencies in the upper portion of the high-frequency (HF) band?
5 and 30 degrees
This is the best way to orient line-of-sight (LOS) antennas
In a straight path to the receiving station
When siting a radio station, which type of foliage would have a more adverse effect on radio-wave propagation?
Broadleaf tree
This has the greatest effect on an antenna’s radiation pattern
Earth
This is one fundamental rule about camouflage
Straight lines are obvious
This is the most effective type of antennas in mountainous terrain that has a mountain between you and the distant end
Near-vertical incidence sky-wave
Which electronic warfare (EW) component responds to a tasking to search for, intercept, identify, and locate intentional and unintentional sources of radiated energy?
Support
Electromagnetic (EM) deception, as it applies to electronic warfare (EW), is
conveying misleading information to an enemy through the deliberate radiation of EM energy
In frequency-hopping (FH) operations, the interval at which each transmitter remains on a given frequency for a specific time is known as
dwell time
Which type of hopping-rate category changes frequencies approximately 100 times per second?
Medium
What does the term “ICOM” indicate?
Integrated communications security
Which statement best identifies the requirements for two transceivers to establish HAVE QUICK (HQ) communications?
They must have the same word of day (WOD) and time of day (TOD)
How long is each word-of-day (WOD) used with the HAVE QUICK II (HQII) communications multiple word-of-day (MWOD)?
24 hours
Which tactical data link (TDL) is a secure, full-duplex, point-to-point digital data link that uses satellite, microwave, or terrestrial cable, as opposed to a modulated waveform, to transmit data?
Link 11b
Which multiple channel access method eliminates the requirement for a net control station (NCS) in the joint tactical information distribution system (JTIDS) by providing node-less communications network architecture?
Time division
The Air Force integrates with modified close air support aircraft with digitized battlefield information using this type of network.
Situation awareness data link (SADL)
Which type of advanced waveform was designed to operate on manned, vehicular-based communication systems?
Wideband networking
Which type of advanced waveform enables data and imagery situational awareness and provides enhanced combat effectiveness?
Soldier radio
In high-frequency (HF) communications, your station’s automatic link establishment (ALE) self-address is the address
the user programmed for his or her station
This is the simplest form of an automatic link establishment (ALE) call
Individual
Which automatic link establishment (ALE) call option lets you call a predefined group of stations with a single shared address, and requires them to respond, one at a time, in a predefined order?
Net
Where is the primary high frequency global communications system (HFGCS) network control station located?
Andrews AFB, Maryland
This is not a major network within the Military Auxiliary Radio Service (MARS)
Ultra-high frequency (UHF) network
The process of unscrambling encrypted information so that it is intelligible is known as
Decryption
Which type of cryptographic algorithm permits the encryption key to be public?
Asymmetric
Which secure communications device operates by simply sliding the key tape into the reader?
KOI-18
The common name for the method of changing encryption keys over the radio channel in a two-way radio system is called
over-the-air-rekeying (OTAR)
Which type of conventional land mobile radio (LMR) device maximizes the communications distance between lower-powered equipment items?
Repeater
In a land mobile radio (LMR) repeater system, a device that separates and isolates the incoming receive signal from the outgoing transmit signal and vice versa is known as a
duplexer
Which type of site configuration was designed to provide coverage for a small geographical area?
Single-site
This provides the interface between dispatch consoles and the central controller in a typical trunking system
Switching equipment
When setting up a trunking network, users with common missions or functions are assigned as
talkgroups
Which statement is not a benefit of having a trunking network?
Unbalanced channel loads
This differentiates the enterprise land mobile radio (ELMR) network from a regular trunking or conventional network
Centralized core controller
Which Air Force instruction (AFI) requires communications squadrons to maintain installation notification and warning systems (INWS)?
AFI 10–2501, Air Force Emergency Management Program
In the giant-voice system, this controls the system’s signal routing and power distribution
Control board
Which is not a major component of the giant-voice system?
Decoder
