How can we help?

You can also find more resources in our Help Center.

102 terms

3D1X3 CDC Volume 2

URE Question Review Cards for RF Transmission Air Force
STUDY
PLAY
Equipment used for generating, amplifying, and transmitting RF carrier is collectively called
a transmitter
What basic receiver function involves having the transmitted electromagnetic wave pass through the receive antenna in such a manner as to induce a voltage in the antenna?
Reception
The ability to reproduce the input signal accurately is the characteristics of the receiver's
fidelity
A combination of a transmitter and receiver that is built as a single unit and sharing common tuned circuits is called a
transceiver
Which of the following cannot be performed by the transceiver's computerized components
and micro-circuitry?
repair itself
A transmission line that consists of a center conductor placed inside a metal tube functioning as the outer tube is called a
rigid coaxial cable.
Which selection best describes the term "cutoff frequency" when discussing transmission
line properties?
The frequency where Xc causes the signal to be shunted
Using figure 1-10, determine the wavelength if the frequency is changed from 150 MHz to
250 MHz.
1.2 meters
Using figure 1-10, determine the electrical length if the frequency is changed from 150
MHz to 250 MHz
8.33 wavelengths
A nonresonant transmission line is a line
having no reflected waves
If a transmission line is terminated in a short
current is at maximum and voltage at minimum at the termination
In a basic communication system, what converts radio frequency (RF) energy's current oscillation into electric and magnetic fields of force?
Antenna
The concept that alternating current (AC) changes in magnitude and reverses its direction during each cycle is
what makes radio transmission possible
If the electric field component travels in a plane perpendicular to the Earth's surface, the radio wave is
vertically polarized
What types of polarization do satellite terminals transmit and receive?
Transmit right hand and receive left hand circular polarizations
What measurement is used to determine whether an antenna is resonant at a particular frequency?
Standing wave ratio.
The ability of an antenna to both receive and transmit equally well is known as the antenna's
reciprocity
The standard used to measure the radiating effectiveness (gain) of an antenna system is the
isotropic antenna
What does the effectiveness of an entire transmitting and receiving system depend largely upon?
Impedance matching
Which antenna radiates radio energy in a circular pattern?
Omnidirectional
Which antenna type is usually used on long-range, point-to-point circuits where the concentrated radio energy is needed for circuitry reliability?
Unidirectional
Ungrounded lengths of wire specifically designed to be either a half-wavelength or more than full wavelength long is called a
Hertz antenna.
A long-wire's takeoff angle depends on the antenna's
length
All antennas used in satellite communications are designed to be
directional
A common satellite antenna is the
parabolic
A helical antenna radiates a signal with what type of polarization?
Circular
Aircraft antennas are housed
inside nonconductive radomes mounted outside or flush with the fuselage.
In airborne antenna applications for frequencies in the upper portion of the HF band, what vertical angles are used for multi-hop, long distance transmission?
5 and 30 degrees.
What determines an antenna's location and orientation on the aircraft?
Optimizing the antenna's radiating pattern for its application.
Which type of airborne antenna can be designed into any part of an aerospace vehicle's surface, so that it does not upset its aerodynamic properties?
Conformal
In selecting an antenna for a circuit, what is the first thing to look at?
type of propagation
Which object has the greatest effect on an antenna?
Earth
Where is the most challenging location for a radio frequency (RF) transmission systems technician to establish and operate a radio station from?
Amazon Jungle
With a mountain between you and the distant end, which antenna is more effective?
Near-vertical incidence skywave
Direct waves are radio waves that travel
through the air in a straight line.
Radio waves that travel near the earth's surface are called
ground waves
Sky wave transmission is used for which type of communications?
Long distance.
The path that undergoes a 180° phase shift is a
ground-reflected path.
Which gives sky wave propagation its ability to communicate beyond the optical line-ofsight (LOS)
Refraction
Frequencies higher than the critical frequency are
passed into space.
In high frequency (HF) communications, the lowest frequency that arrives at the distant receiver on 90 percent of the undisturbed days of the month is called the
lowest usable frequency (LUF).
The abbreviation FOT is derived from the term
frequency of optimum transmission
Magneton splitting creates two waves called
ordinary and extraordinary
What occurs when a transmitted signal travels over two or more separate paths during transmission?
Multipathing
What is the recombination process dependent upon?
Time of day.
Which layer of the ionosphere is most important to high frequency (HF) communications?
F
During what season do we have the wider range of critical frequencies and less absorption of all frequencies?
Winter
Sunspots are disturbances
on the sun's surface
For communications purposes, the usable frequency spectrum ranges from
3 hertz (Hz) to 300 gigahertz (GHz+.
What U.S. government agency divides the radio frequency (RF) spectrum into different bands?
Federal Communications Commission.
Near-vertical-incidence sky (NVIS) wave operations are most effective when you're using
lower high frequency (HF) frequencies.
What frequency band is most susceptible to jamming?
High frequency.
What frequency bands does the MILSTAR satellite system use?
Super-high frequency (SHF) and extremely high frequency (EHF).
The main very high frequency (VHF)/ultra high frequency (UHF) communications emphasis is on
air-ground communications.
Super high frequency (SHF)/extremely high frequency (EHF) range is limited to
line-of-sight (LOS).
In a move to overcome the limited range of forward propagation by tropospheric scatter (FPTS) without requiring many costly relay systems, what was developed?
Satellite communications
Why isn't very high frequency (VHF) normally used for satellite communications?
Ionospheric refraction can occur
When comparing the radio and optical horizons, which one is farther away and by what percent?
Radio; 15
When K is greater than 4/3, the radio horizon will
increase
A radio wave originated at a center source in free space. If the field strength at one mile
from the source has a field strength of 100 microvolts per meter, what is the field strength at two
miles?
50 microvolts per meter
Any military action involving the use of the electromagnetic (EM) spectrum to include directed energy to attack an enemy is called
electronic warfare (EW).
Which is not an example of electronic protection (EP)?
Communications intelligence.
Which electronic warfare (EW) component responds to taskings to search for, intercept,
identify, and locate intentional and unintentional sources of radiated energy?
Electronic support (ES).
Electromagnetic (EM) deception as it applies to electronic warfare (EW) is
the deliberate radiation of EM energy intended to convey misleading information to an enemy.
What is the process of unscrambling encrypted information so that it is intelligible?
Decryption
How many selectable traffic key slots does the KG-84A have?
4
Which switch on the KY-57 VINSON zeroizes channels one through five?
Fill
The common name for the method of changing the encryption keys over the radio channel in a two-way radio system is called
over-the-air-rekeying (OTAR).
Centralized control of encryption keys will not reduce
safety problems.
In frequency hopping (FH) operation, the interval at which each transmitter remains on a given frequency for a specific time is known as the
dwell time
Which RT-1523 SINCGARS subassembly removes synchronization and frequency hopping information that is embedded in a receive signal?
The interleaver.
The RT-1523 SINCGARS radio's time sync and correlator module manipulates control signal outputs during the frequency hopping (FH) mode to
shut down reception and transmission during frequency shifts.
Concerning HAVE QUICK II communications (MWOD), how long can each word of day (WOD) be used?
For 24 hours.
Which one of the following statement is not a characteristic of the AN/GRC-171B(V)4
transceiver?
It operates from 116 MHz to 149.975 megahertz (MHz). It DOES operate from (225 MHz to 399.975 MHz
What does the low-pass filter of the AN/GRC-171B(V)4 transceiver perform?
Image frequency rejection in receive and harmonic attenuation in transmit
The output power of the AN/GRC-171B(V)4 transceiver is
20 Watts in AM, 50 Watts in FM
The Joint Tactical Information Distribution System (JTIDS) is commonly referred to as
Link 16
Which service uses the Enhanced Position Location Reporting System (EPLRS) to locate and track amphibious assault craft?
Navy
What type of network radio does the Air Force use for close air support?
Situation Awareness Data Link (SADL).
How many programmable devices can the multiband inter/intra team radio hold?
7
What must the primary and remote annunciators be capable of in an intrusion detection system (IDS)?
Operate independently of one another.
On a sensor system the annunciation display must be able to differentiate between
alarms and tampers
The interior sensor that operates on a principle of magnetic fields imposed on a reed switch is a
balanced magnetic switch.
Which personnel identification device provides positive identification through measurement of biometrics?
Hand geometry unit (HGU).
On the advanced entry control system (AECS), which panel configuration monitors sensors and reports any alarm conditions detected?
Intrusion detection.
What device on the advanced entry control system (AECS) allows the operator to install, review, modify, and broadcast databases created to all other workstations?
System administrator terminal.
How many hours of power must the uninterrupted power supply (UPS) in an advanced entry control system (AECS) provide in the event that the station power is lost?
6
Which site configuration was designed to provide coverage for a small geographical area?
Single-site.
What provides the interface between dispatch consoles and the central controller in a trunking system?
Switching equipment.
How many talkgroups can a trunked mobile radio monitor at one time?
1
What has the ability to patch different talkgroups together?
Dispatch console.
What Air Force instruction (AFI) requires communications squadrons to maintain "installation warning systems"?
AFI 10-2501.
What is a common problem with a mass alert system in a deployed environment?
Cleanliness
In the Whelen siren stacks, what size driver does a speaker cell contain?
400-watt
In the Whelen siren cabinet, what controls signal routing and power distribution of the system?
Motherboard
With the Whelen configuration software, which tabs allow you to troubleshoot the system?
Status and dual tone multi-frequency (DTMF)
In high frequency (HF) communications, your station's self address is
user programmed into your system.
We define link quality analysis (LQA) as
the process of sounding and determining channel clarity.
What is the maximum power of the AN/PRC-150 in frequency modulation (FM) mode
10 watts.
Where do the modulation and digital-to-analog (D/A) conversion take place in the AN/PRC-150?
Signal process and control module
wavelength (λ)
λ= 300/frequency in MHz
Electric Length
E.L.= Physical Length/λ