3D1X3 CDC Volume 2

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102 terms · URE Question Review Cards for RF Transmission Air Force

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

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