Flashcards in CDC 3D153 v2 Deck (276):
Define communications system.
A group of related components designed to transfer information from one point to another.
Name the transmitter requirements for successful communications.
Relatively stable in frequency and amplitude and free from excessive noise, harmonics, and spurious outputs.
Name the five basic functions of a communications receiver.
Reception, selection, detection, amplification, and reproduction.
What is the difference between a receiver’s selectivity and its sensitivity?
Sensitivity—the ability of a receiver to reproduce the signal of a very weak station.
Selectivity—the ability of a receiver to select and reproduce a desired signal from several closely spaced stations or from interfering frequencies.
What is a transceiver?
A transceiver is a combination of a transmitter and a receiver built as a single unit and sharing common tuned circuits.
What has also allowed our transceivers to become lighter, smaller, and easier to operate?
Define "transmission line" and give an example of one.
A conductor or series of conductors used to carry energy from a source to a load. Examples include the flexible coaxial cable, the rigid coaxial cable, an AC power cord on a stereo, a cable television wire, and a telephone cord.
What are the major power losses in a flexible coaxial cable?
The dielectric and skin effect.
Why is there very little radiation loss in a rigid coaxial cable?
Because the energy is confined between the two conductors.
At what frequencies are waveguides used?
For frequencies so high that their wavelength is miniscule.
What physical properties determine the characteristics of a rectangular waveguide?
Internal height and width.
What effect does internal moisture have on a waveguide?
It can cause serious arching.
Identify the primary determinants of a line’s capacitance.
The amount of capacitance is primarily determined by the size of the conductors, the space between them, plus the dielectric material.
What determines ZO of a transmission line?
Its series inductance and shunt capacitance.
Describe how a transmission line’s characteristic impedance is affected by changing its physical length.
Changing the physical length of a transmission line has no effect on characteristic impedance.
What does "cutoff frequency" refer to when talking about transmission lines?
The frequency at which the value of XL and XC are such that the signals will be developed across the series inductance and shunted by the capacitance and, thus, not pass along the line.
The distance in space occupied by one cycle of a radio wave at any given instant.
As signal frequency decreases, what happens to wavelength?
What is the unit of measure for electrical length?
Number of wavelengths.
If the transmission line’s physical length remains constant, what happens to electrical length as frequency decreases?
Electrical length decreases.
Describe a nonresonant transmission line.
It is a line having no reflected waves.
What is an incident wave?
Voltage and current waves as they move from source to load.
What is a standing wave?
It is the vector sum of the forward and reflected waves.
This is a comparison (expressed as a ratio) of the maximum and minimum voltages found along the lines.
If a transmission line has a perfect impedance match, what would the VSWR be?
What will likely happen with a high VSWR?
A high VSWR not only causes communications to fail, it can also damage the equipment or transmission line.
At what level will voltage be at an open termination?
Voltage will be at maximum across an open.
What is the phase relationship between forward and reflected voltage waves when the line is terminated in a short?
Voltage is reflected 180° out of phase.
What is the purpose of the antenna?
It is a transducer; it converts RF energy as current oscillations into electric and magnetic fields of force.
In radio communications, which major force fields are we concerned with?
Electric and magnetic.
What is the relationship between the electric and magnetic fields?
If an electric field is changing, a magnetic field is created; if a magnetic field is changing, an electric field is created.
Which type of electric current continually changes in size and direction?
Alternate current is continually changing in size and periodically changing in direction.
Define radio waves.
EM fields of force; that is, magnetic fields generated by continually changing electric fields.
What happens to magnetic fields above approximately 10,000 cps?
They are radiated from the conductor in the form of radio waves.
Describe the induction and radiation fields.
The radiation field detaches from the antenna and travels through space. The induction field is the portion of the EM field that immediately surrounds the antenna and collapses completely when the antenna voltage and current reverse.
At what distance from the antenna are the induction field and the radiation field the same strength?
One-sixth of a wavelength from the antenna.
Explain the rate of decrease in the two fields’ strengths as the distance from the antenna increases.
The induction field decreases as the square of the distance increases. The radiation field decreases linearly with distance.
What are the determining factors that affect the pattern of radiation?
Antenna design, the earth, and surrounding objects affect the direction of radiation.
What is the polarization if the E field component travels in a plane parallel to the Earth’s surface?
How can an antenna receive a maximum transfer of energy from the EM fields?
An antenna needs to be in the proper plane of polarization for maximum transfer of energy from the EM fields.
Describe circular polarization.
In a circularly polarized antenna, the plane of polarization rotates in a corkscrew pattern, making one complete revolution during each wavelength. A circular polarized wave radiates energy in both the
horizontal and vertical planes and all planes in between.
Differentiate between a resonant and nonresonant antenna?
In a resonant antenna, almost the entire radio signal fed to the antenna is radiated. If the antenna is fed with a frequency other than its designed frequency, much of the signal is lost and is not radiated.
What is the frequency range of a resonant antenna?
The frequency of a resonant antenna effectively radiates a radio signal for frequencies close to its designed frequency, usually within a range of plus or minus 2 percent.
What is a frequency independent antenna?
A nonresonant antenna designed to operate over a wide range of frequencies using maximum power is known as a frequency independent antenna.
In the real world, what is the ideal standing wave ratio?
1.1 to 1.
What is the fundamental frequency of an antenna?
The lowest frequency at which it resonates.
What is the concept of antenna reciprocity?
The more efficient it is for transmitting, the more efficient it is for receiving.
What is an isotropic antenna?
A theoretical antenna that radiates equally well in all directions.
How can an antenna deliver twice as much power to the receiving antenna?
The antenna does this by redirecting the energy from other directions.
What allows all available power to be absorbed and radiated by the antenna without reflections back down the line?
Proper impedance match.
Describe an antenna coupler.
A coupler is a matching device inserted between a transmitter and its antenna to make a transmitter "think" it is connected to a low-SWR antenna.
What can you use to match a 50-ohm cable to a 600-ohm antenna?
A balun can be used to match the impedance.
Describe each classification of antenna in accordance with its radiation pattern.
An omnidirectional antenna radiates radio energy in a circular pattern. A bidirectional antenna has two main lobes, with nulls between them. A unidirectional antenna has a single large lobe in one direction and
greatly reduced lobes or nulls in other directions.
Why would you use an omnidirectional antenna?
The omnidirectional antenna is used when it is necessary to communicate in several different directions at once, such as an ATC tower or operating in a multi-station net.
Give examples of a deployable bidirectional antenna.
Deployable bi-directional antennas are usually the inverted-V or center-fed, half-wave dipole.
What is the biggest factor about setting up unidirectional antennas?
Since a unidirectional antenna concentrates almost all the radio signal in one specific direction, it must be carefully oriented.
How can you make a long-wire antenna directional?
A long-wire antenna can also be made directional by placing a terminating resistor at the distant end of the antenna.
The beamwidth of a directive antenna is the width in degrees, of the major lobe between the two direction at which the relative radiated power is equal to one-half its value at the peak of the lobe.
What are the two basic types of antenna?
Hertz and Marconi.
What are Hertz antenna specifically designed for?
Hertz antennas are ungrounded lengths of wire specifically designed to be either a half-wavelength long, such as a dipole or doublet antenna or more than a full wavelength long, such as a long-wire antenna.
How did Mr. Marconi overcome great antenna heights at lower RF ranges?
Mr. Marconi found that when a quarter-wave vertical antenna has its base on the ground, the earth below the antenna acts like a large reflector (or mirror) and supplies another quarter-wavelength. In effect, the quarter-wave vertical antenna acts like a half-wave antenna.
What is the most commonly used HF antenna for covering short distances in a tactical environment?
Which HF antenna is a complicated multidipole array that’s often used in high-powered fixed radio stations?
When an LPA receives a certain frequency, which parts of the log periodic antenna are actually being used?
Only the parts of the LPA that are resonant to the operating frequency are actually being used.
What reduces the gain and efficiency of half-wave dipole antenna?
Excessive antenna sag can actually reduce the gain and efficiency of a half-wave dipole antenna.
Describe multiband half-wave dipole antenna?
When space or other resources aren’t adequate to erect separate dipoles, you can combine three or four dipoles to occupy the space normally required for one. Each wire in a multiband dipole is cut to a halfwavelength of an assigned frequency. All the separate antennas are connected to the same antenna feed block or connector and are fed by a single transmission line.
Define inverted-V antenna?
The inverted-V is a half-wave dipole, supported in the center by a single mast, with both antenna legs anchored near the ground. It is designed and cut for a specific frequency and has a bandwidth of plus or
minus 2 percent.
What is the minimum length of a long-wire antenna?
A half -wavelength.
How many wavelengths are required to produce the best results on a sloping long-wire?
The sloping wire produces best results when it is more than two wavelengths long.
What improvements does the sloping V offer over the standard long-wire antenna?
Sloping V long-wire version is an improvement over the standard long wire and the sloping long wire, in that the two legs tend to reinforce each other for improved performance and increased effective radiated power.
Which elements on the inverted L antenna provide omnidirectional radiation for ground-wave propagation and high-angle radiation for short-range sky wave propagation?
Inverted L antenna provides omnidirectional radiation for ground-wave propagation from the vertical element and high-angle radiation from the horizontal element for short-range sky wave propagation.
What is a NVIS antenna?
The NVIS omnidirectional antenna is a HF high-angle radiation and low operating frequencies antenna.
What are all satellite communications antennas designed to be?
Highly directional and high-gain in order to overcome free-space loss affecting satellite systems.
What is the basic principle of all parabolic antennas?
Reflection of a radio signal for controlled directivity.
Which type of polarization does a helical satellite antenna uses to radiate a signal?
What is the horn antenna used for?
In the transmission and reception of RF microwave signals.
What are the typical applications for airborne antennas?
Wideband and satellite communications; telemetry data collection, tracking, and signal relay; timing signal reception; and satellite navigation signal reception.
What angles should the signal arrive at the aircraft antenna for frequencies in the lower portions of the HF band?
Vertical angles between 20 and 60 degrees above the horizon.
Where on the aircraft is the vertical whip antenna typically mounted?
Typically, on top of the aircraft’s fuselage.
What are two problems associated with airborne antenna operating above HF?
1. A serious problem at these frequencies involves the interference between the direct ray and groundreflected ray. As a result, a receiver in an aircraft which approaches a ground station from a considerable distance at a constant altitude will experience a marked rise and fall in signal strength as the aircraft moves in.
2. Another difficult problem is the aircraft antenna design. Obstructions forming part of the airframe produces undesired shadows and diffraction effects. In addition, reflections from these obstructions produce interference effects that result in many lobes.
What types of application use the fixed-blade and other low-profile antenna styles?
Fixed-blade and other low-profile antenna styles are used for such things as UHF/SHF satellite communications, telemetry data relay, transponder tracking, and global positioning system navigation.
Where on the aircraft would satellite communications antennas be mounted?
On the top of the aircraft.
Which type of antenna is mounted on the nose of the aircraft?
A steerable parabolic dish antenna used for telemetry tracking is mounted in an aircraft’s nose.
What antenna has a unique design where the antenna becomes part of the skin of the vehicle?
A unique antenna design where the antenna becomes part of the skin of the vehicle is the conformal antenna.
What is the first thing you look at when selecting an antenna for an HF circuit?
The type of propagation.
What is the first step in selecting an antenna for HF sky wave propagation?
Find the distance of the circuit so that you can find the required takeoff angle.
Describe the ideal antenna site selection setting.
A clear, flat area with no trees, buildings, fences, power lines, or mountains.
Name the 5 steps in the HF sky wave antenna selection process?
HF sky wave antenna selection involves:
1. Determining the range.
2. Determining the type of coverage (omnidirectional, bidirectional, directional).
3. Determining the operating frequency.
4. Determining the takeoff angle required to clear site obstacles.
5. Selecting the antenna with the highest gain at the required takeoff angle that can be erected on the
available site with the available materials.
Differentiate the one-half wavelength above the ground and the one-quarter wavelength above the ground radiation pattern of a dipole antenna.
When a half-wave dipole antenna is placed one-half wavelength above the ground, the radiation pattern has two main lobes. When it’s lowered to a quarter-wavelength above the ground, the radiation is directed
upwards in one large lobe.
What is the gain of an 8-meter vertical dipole antenna at 18 MHz and a radiation angle of 30°?
For a LOS system (microwave), what determines if a repeater is necessary?
The distance to be spanned and the terrain.
What kind of location should you pick for a tactical antenna that uses frequencies above 30 MHz?
One that allows LOS communications.
Why does dry ground limit a radio set’s range?
Dry ground has high resistance and limits the range of the radio set.
What object has the greatest effect on an antenna?
Why shouldn’t you use sawed-off branches and foliage for camouflage?
The leaves soon wilt, change color, and become conspicuous against the natural growth.
To what level can the poor electrical ground caused by the dry, sandy soil of a desert reduce the effectiveness of a whip antenna?
As little as one-third of its normal efficiency.
In mountainous areas with high winds, what should you do to the antenna masts?
Secure the masts with extra guy ropes in anticipation of high winds.
What causes sensitive components to either malfunction or get out of alignment?
Which radio wave travels near the earth's surface of the earth and are greatly affected by the earth’s conductivity?
Since ground waves travel near the surface of the earth, they’re greatly affected by the earth’s conductivity and by any obstruction (such as mountains or buildings) on its surface.
What are the limiting factors for direct wave communications?
Direct waves continue to travel in a straight line until they are interrupted by an object or weaken over a great distance. The average distance of direct wave communications is therefore limited by the height of the transmit or receive antenna.
What determines the earth’s conductivity?
The type of soil and water in the propagation path.
Name the radio wave used in long-distance communications.
Sky wave transmissions are very effective for long-distance communications in the HF range (3 – 30 MHz).
What frequency is used for ground wave propagation?
Low and very low frequencies.
How we extend LOS distance?
Increasing the height of the transmitting antenna, the receiving antenna, or both.
What is the best type of surface for surface wave transmission?
What gives sky wave propagation its ability to communicate beyond the optical LOS?
Describe the skip zone.
The area between the most distant point reached by the ground waves of a particular signal and the point at which the ionospheric wave first returns to the earth. In this zone, you would experience a zone of silence because no radio signals are received.
Define skip distance.
The distance from the transmitter to the point at which the refracted sky-wave first returns to earth.
What is the primary loss from multihop transmission?
Each time a hop is made, considerable signal strength loss occurs. This loss results primarily from absorption.
What causes the cancellation and summation effects of the received signal to occur at the receiver?
Because of the relative amplitude and phase differences of these various signals.
Which type of fading is a function of frequency?
List the five basic regions that make up the atmosphere.
The troposphere, stratosphere, ionosphere, mesosphere and thermosphere.
How are long-distance HF communications made possible?
By reflections/refractions of radio waves from ionized layers in the ionosphere.
What causes the different ionospheric layers?
The different wavelengths of ultraviolet rays expanding their energy at different heights within the atmosphere.
The recombination process is dependent on what?
Time of day.
Name the different layers within the ionosphere?
D, E, F1, F2 and the topside.
How is the E layer broken down?
It is broken down into a thick E2 layer and a highly variable thin layer called Sporadic E.
Describe the difference between the two general types of ionospheric variations.
Regular variations can be predicted in advance with reasonable accuracy. Irregular variations are those that result from abnormal variations and cannot be predicted in advance.
What happens to the ionospheric layers when solar activities are no longer present?
When solar activity is no longer present the D, E, and F1 layers disappear, leaving only the F2 layer. The F2 layer decreases in altitude with the setting sun, and combines with the remnants of the F1 layer to form a single nighttime F layer.
What is the length of the sunspot cycle?
Every 11 years.
Solar flares produce what?
A burst of radiation across the EM spectrum.
Which layer do ionospheric storms mainly affect?
The higher F2 layer, reducing its ion density.
What is the exact cause of the Sporadic E?
Its not known.
For communications purposes, what is the usable frequency spectrum?
3 Hz through 300 GHz, and up to about 100 THz Tera Hertz.
What organization regulates the use of the frequency spectrum by all nations?
International Telecommunications Union (ITU).
What is the audio frequency range?
15 Hz and 20,000 Hz.
How are ELF transmissions propagated?
Through the earth’s substrate.
What determines the range of MF propagation?
Transmit output power and atmospheric conditions.
What is the frequency range of the HF frequency band?
What determines the distance HF sky waves can propagate?
Atmospheric conditions and the frequency used.
Why are HF communications not considered suitable for critical C2 systems?
The inherent vulnerability of intercept and jamming.
What is the general rule to remember when using the VHF frequency band?
The higher the frequency, the less power required to transmit VHF signals over a given distance.
Name a satellite system that is currently using the EHF frequency range?
What is the general rule of thumb for radio wave propagation as frequencies increase from HF to VHF?
Propagation takes on more of the characteristics of LOS.
What is the approximate air-to-ground range of VHF/UHF communications?
What is the primary transmission path for frequencies in the SHF/EHF range?
The direct wave.
Give an example of a SHF communications system.
Defense Satellite Communications System (DSCS) III.
Explain the reason for the difference in distance between the optical and radio horizon.
The slight bending of the transmitted waves in the lower atmosphere.
Which principle of communications was developed to overcome the LOS distance disadvantage?
Forward propagation by tropospheric scatter (FPTS).
Why is the principle of reflection very useful in the design of directional antennas?
Reflection allows the waves to be focused into a beam.
What happens to the speed of a propagated wave as the atmosphere becomes less dense?
How much farther is the radio horizon than the true horizon in a standard atmosphere?
What effect happens to the radio horizon if K experiences a significant decrease in value?
It decreases along with the value of K.
Which propagation characteristic permits communications in shadow regions behind obstacles?
Which propagation characteristic permits communications in shadow regions behind obstacles?
The presence of moisture particles such as rain, snow, and clouds in the transmission path.
In super refraction, what will decrease from the standard?
If the atmosphere’s temperature increases with height (inversion) and/or the water vapor content decreases rapidly with height, the refractivity gradient will decrease from the standard.
Describe how ducting can occur.
During a temperature or humidity inversion, thicker air is on top instead of on the bottom. Instead of downward, a radio wave entering this inversion is bent upwards, out of the LOS transmission path. If propagated radio waves encounter another atmospheric layer above the inversion layer, they could be refracted (bounced) back and forth between the boundaries of the two layers.
What is free space loss?
If radio waves could originate at a center source in free space, they would spread out in ever-growing spheres from the source. In free space the intensity of the field of the radio wave decreases directly with the distance from the source. This decrease in field strength is caused by spread of wave energy over larger and
larger spheres as the distance from the source in increased.
Why is the free space path loss increases with the square of the frequency?
The frequency dependence solely based on the decreasing effective aperture of the receiving antenna as the frequency increases. This is because the physical size of an antenna type is inversely proportional to frequency.
What is the major loss in satellite and tropospheric communications?
Free space loss.
How do receivers overcome Doppler shift?
The receiver needs to accommodate the maximum expected Doppler shift. It needs either sufficient bandwidth or a means of following the frequency shift.
What is the average distance between stations using direct wave communications?
20 to 30 miles.
What is electronic warfare?
Any military action involving the use of the EM spectrum to include DE to control the EM spectrum or to attack an enemy.
How does EA prevent or reduce an enemy’s use of the EM spectrum?
Detection, denial, disruption, deception, and destruction.
What is the key element in preventing jamming by friendly forces?
Proper frequency management.
Give some examples of EP.
Frequency agility in a radio, change pulse repetition frequency on a radar set, electronic and material shielding for systems, and processes to counter meaconing, interference, jamming, and intrusion.
What taskings do ES respond to?
Search for, intercept, identify, and locate sources of intentional and unintentional radiated EM energy for the purpose of threat recognition.
What EW effects are waged throughout the electromagnetic spectrum to secure and maintain effective control and use?
Through the integration of detection, denial, deception, disruption, and destruction.
Define EM deception as it applies to EW.
The deliberate radiation, reradiation, alteration, suppression, absorption, denial, enhancement, or reflection of EM energy in a manner intended to convey misleading information to an enemy or to enemy EMdependent weapons, thereby degrading or neutralizing the enemy’s combat capability.
The process of scrambling information so it is unintelligible to anyone except the intended recipient.
What is secure voice?
Devices which are designed to provide voice encryption for voice communication over a range of communication types such as radio, telephone or IP.
Describe the difference between symmetric and asymmetric algorithms?
Symmetric algorithms use the same key for both encryption and decryption where the decryption key is derived from encryption key. Asymmetric algorithms use a different key for encryption and decryption, the decryption key cannt be derived from the encryption key.
What permits the encryption key to be public and the decryption key to be private?
Asymmetric algorithms permit the encryption key to be public, allowing anyone to encrypt with the key,
but the decryption key is private so only the intended recipient can decrypt the message.
Describe the difference between “keyed” and “unkeyed” encryption devices.
When an encryption device is appropriately configured with the proper codes, it is considered to be “keyed.” Absence of this configuration code renders the device useless; it is then considered to be “unkeyed.”
If the operator uses a TOP SECRET code key, what security classification would the device take?
If the operator uses a TOP SECRET code key, the device is considered TOP SECRET.
How is COMSEC hardware categorized when it is empty and free of codes?
Cryptographic controlled item (CCI).
Describe the KY–99 encryption device?
A self-contained terminal with embedded communication security and is designed to provide secure voice and/or data communications for military customers.
Which encryption device is a general, high-capacity key generator used to encrypt and decrypt teletypewriter and digital data in both tactical and fixed environments?
What does the mode switch on a KY–57 do?
It allows you to transmit in the clear and secure mode and it controls the loading of encryption codes.
When the cryptographic ignition key is removed and not collocated, how should the KIV–7 be handled?
As an UNCLASSIFIED cryptographic controlled item (CCI).
How do you operate a KOI–18?
Slide the key tape into the reader and pull it out at a moderate rate.
How do you verify the presence of a code in a KYK–13?
The red indicator light blinks when you press the initiate button in the OFF/CHECK position.
What is one advantage of the CYZ–10?
You can carry hundreds of fills
What is OTAR?
Method of changing the encryption keys in a two-way radio system over the radio channel or over the air.
What does OTAR give you?
A centralized control over encryption keys which reduces procedural, operational, and security problems.
What does the FH signal to a receiver that is not synchronized to the transmitter look like?
What type of techniques makes the HAVE QUICK and SINCGARS radios effective against jamming, compared to older systems?
What is the hopping speed of the fast FH mode?
More than 1,000 hops/sec.
Name the types of spread spectrum systems.
Direct sequence, FH, time hopping, pulsed FM (chirp), and hybrid systems.
What type of system uses a combination of spread spectrum methods to use the beneficial properties of the systems used?
What four properties arise as a result of the pseudorandom code sequence and the wide signal bandwidth that results from spreading?
Selective addressing code, division multiplexing, low probability of intercept, and antijamming.
What does the acronym “ICOM” indicate?
Integrated COMSEC capability.
Which section of the RT–1523 is responsible for modulation and demodulation?
The RF section.
State the purpose of the interleaver during receiver operations.
Removal of synchronization and frequency-hopping information that is embedded in the signal.
How many different impedance bands are contained in the impedance matching network?
Which band of the impedance matching network is used if a BNC-type connector is connected to the RT?
The 50-ohm band.
State two conditions which will cause the SIDETONE DISABLE line to be set to logic level 1.
Temperature exceeding 105° Celsius or VSWR exceeding 5:1.
Name the 3 items used to select a frequency from the look-up table during FH mode.
The TRANSEC variable, FH sync time (TOD), and net ID number.
Where does the control module obtain and execute instructions during remote operation?
From the remote I/O module.
Which RF section module performs modulation of the carrier?
The exciter/power amplifier.
State the purpose of HAVE QUICK radios.
To prevent unfriendly forces from interfering with our communications.
What is the purpose of WOD and TOD?
The radios use WOD and TOD to decide which frequency they should be on at any given time.
Why isn’t HAVE QUICK considered a means of secure communications?
Broadband spectrum analyzers can quickly “see” each frequency as it is being used and thereby “listen” to the communications. A determined enemy can tune 7,000 receivers to the proper frequencies and listen to the communications.
List two differences between HQI and HQII.
HQ1 allows one word to be loaded at a time; the word has no time limit for how long it can be used. HQII allows up to six words to be loaded at a time and each word expires after 24 hours.
Which module of the AN/GRC–171B(V)4 controls all activities of the transceiver?
The ECCM module.
What is the RF output power when in FM mode?
What happens to the guard receiver when the transceiver is keyed?
The guard receiver is disabled.
Which module determines frequency selection when in the HAVE QUICK mode?
The ECCM processor.
What causes all 6s to be displayed on the FREQ/CHAN display?
An over temperature condition.
What does it mean if the FAULT lamp comes on?
It indicates an out-of-tolerance condition exists.
What is JTIDS commonly referred to?
State the principle of operation that eliminates the requirement for a net control station?
TDMA eliminates the requirement for a net control station (NCS) by providing nodeless communications network architecture.
What acts as the single time source for time synchronization of all units entering the network?
Network Time Reference (NTR).
What makes JTIDS resistant to jamming?
Spread-spectrum and FH techniques.
The JTIDS terminal operates in what frequency band?
L-band (between 960 and 1215 MHz.
Describe the enhanced position location reporting system.
EPLRS is a joint service, software programmable, networking digital radio. It provides secure, jam-resistant wireless digital connection among battlefield computers; allowing field commander’s to form a joint network. Also, it provides platform position information independent of GPS. EPLRS aids in fratricide
prevention because it is highly jam resistant and thus allows weapons platforms to see where other EPLRS
are located even in a congested battlefield environment.
What are the EPLRS system virtual circuits called?
Needlines, to set up communications between EPLRS RSs.
Who controls the EPLRS control network, performs all the necessary calculations, routes control net messages and queries, and graphically displays the positions of all active RSs?
EPLRS network manager.
Name the four features the EPLRS radio sets provide.
The radio sets provide the following features:
1. Display user position location with accuracy of 10 to 30 meters for manpack, surface vehicle, and grid
reference RS and 25 to 100 meters for airborne RS.
2. Provide automatic reporting of RS position location.
3. Provide user-to-user digital readout communications.
4. Provide range and bearing to other RS, designated reference points, or predesignated positions.
Describe the situational awareness data link (SADL).
SADL integrates modified US Air Force close air support aircraft with the digitized battlefield information via EPLRS on their heads up display showing where Army/Marine/ground radios are located.
What is the ultimate goal for the joint tactical radio system family of radios?
To produce a family of interoperable, modular, software-defined radios that operate as nodes in a network to ensure secure wireless communication and networking services for mobile and fixed forces.
What does legacy interoperability deal with?
Legacy interoperability deals with the ability for JTR sets to communicate with designated radios currently fielded and, more specifically, the waveforms associated with each of those radios.
What can each channel of a JTR capable of executing?
Each channel of a JTR is capable (in general) of executing a different waveform (e.g. WNW, EPLRS, etc.) depending on the mission requirements determined by the operator.
How many programmable devices can MBITR hold?
Being software-based, MBITR holds seven programmable devices.
What factors should you consider when planning the installation of IDS?
Equipment capabilities and limitations, mission criticality, and threat to the resources that are to be protected.
How does IDS assist SF capabilities?
By alerting security personnel to an approach, intrusion, or attempted intrusion.
What type of system should the installed IDS be?
A “closed” system, not allowing access from external source.
What is the main purpose of a boundary fence?
To present a physical and psychological deterrent to unauthorized entry.
What does a clear zone consists of?
A 30 foot area inside and outside the site perimeter fence.
For what purpose does the area lighting need to illuminate the interior of the restricted area?
To help personnel detect and track intruders.
What must a line of detection detect?
A person walking, running, rolling, crawling across, or jumping through the line of detection.
Where are CCTVs typically located?
CCTVs are typically located along exterior site perimeter clear zones, at controlled access points to sites or buildings, within a restricted area that overlooks selected security areas outside, and at selected locations within the protected areas indoor.
What is the purpose of an entry control facility?
To assist SFs in controlling entry in to and exit from restricted areas.
What components make up a simple portal?
Single door, a turnstile, or a pedestrian or vehicle gate.
What personnel identification device can be used at portals to read the encoded magnetic stripe on badges?
The card reader PIN pad/prompt.
List the four card reader Pin/pad/prompt configurations used with the AECS.
1. Card reader with prompt display.
2. PIN pad with prompt display.
3. Prompt display only.
4. Card reader with PIN pad and prompt display.
Which panel configuration locks and unlocks portals based on inspection of personnel credentials such as magnetic stripe-encoded badges, PIN entries, or biometric measurements?
The portal control panel (PCP).
What workstation functions as a central file server and communicates directly to the CSC workstation?
The enrollment master station (EMS).
Which workstation displays events and assists the operator in responding to these events?
What audio subsystem component is typically located at access portals enabling persons attempting entrance to a controlled area?
What allows the camera inputs to the video switches located at the CSC, MSCF, and ECP workstations to be forwarded to another station?
What devices are used to accommodate large geographical separations between workstations and panels?
Modems and fiber optic transceivers.
What backup power voltage do the primary and backup power supplies provide in the event that station power is lost?
What are some of the advantages of a conventional LMR system?
They are cost effective, they are easy to maintain, and their limited infrastructure ensures that communication is possible in the event of a catastrophic failure.
When you key and speak into a radio, who can hear you?
Everyone on that particular channel can hear you.
When would you use a simplex radio system?
Simplex radio system works well when there are only a few users who are closely located.
In a half-duplex operation, what are the two frequencies used for?
Transmissions take place on one frequency and receive on another.
Why do repeaters use duplexer?
With a duplexer, it isolates the receiver from “hearing” the transmitter and prevents damage to the receiver.
What are the limitations of a single-site configuration?
The user radio must be within the range of coverage of the repeater, base station, or other radio asset.
What system is employed to increase area coverage and to improve radios talkback capability?
To extend the coverage of an area and improve its talkback capability, a receiver voting system is employed to the existing LMR architecture.
Describe the primary difference between a simulcast and multicast system?
While a simulcast system transmits on the same RF channels simultaneously from each base station/repeater, multicast systems use different RF channels at each site.
What does a typical trunking system consist of?
Some type of access control (whether in each mobile unit or centralized at a base station site), switching equipment, system management computer, control and voice channel repeaters, modems, and telephone
When you set up a trunking network, how are different user groups defined?
User groups are defined as “talkgroups.”
What is trunking?
Electronically controlled sharing of a relatively small number of communications channels among a relatively large number of users.
How does trunking result in a more balanced load sharing?
Trunked systems use access control schemes to share channel capacity among many users. The electronic control enables users to take advantage of some transmitted channels that are idle at a particular time while others are busy.
What part of the trunking system sends a data message over the control channel to automatically switch all radios in a particular talk group to the available voice channel?
If a voice channel is available, the system controller sends a data message over the control channel switching all units in User A’s talk group to the available voice channel.
Besides spectrum conservation, what are the other inherent benefits of a trunking system?
Other inherent benefits include faster system access, better channel efficiency, more user privacy, flexibility to expand, and selective radio inhibit.
On the radio, what does the scan function do?
Cycles through the talkgroups programmed in the scan function but again they are only monitoring one talkgroup at a time.
Which trunking user equipment provides users the capability to monitor more than one talkgroup at a time?
Dispatch consoles provide the capability to monitor more than one talkgroup at a time.
How are LMR radios rekeyed without having to physically recall the radios from the field?
LMR radios can support over-the-air rekeying of encryption keys without having to physically recall the radios from the field.
What does giant voice provide?
The base with crucial safety and security information.
What AFI requires communication squadrons to maintain “installation warning systems”?
AFI 10–2501, Full Spectrum Threat Response Planning and Operations.
Besides maintaining “installation warning systems,” what else must a communications squadron do?
To originate, verify, and maintain an audibility footprint map showing area of coverage and low audible/hazard areas.
What is one of the common problems with mass alert systems in a deployed environment?
What are the three basic components of a Whelen system?
Siren stacks, siren cabinet, the encoder.
Differentiate the operation between the remote and local position of the WPS–2800 system?
There are two ways to operate the WPS–2800 system, remote or local position. Remote position operation involves transmitting signals from the encoder to the desired station via a landline connection or through FM transceivers. Local position operation is accomplished through the control panel on the front of the siren cabinet.
How long does the E–969 encoder maintain current time when power is lost?
Up to three months.
Name the two ways you can program the E–969 encoder.
Through a personal computer or through the encoder’s keypad.
How many call keys does the E–2010 have?
What is automatic link establishment?
A means of automatically establishing an HF link between two or more stations with minimum operator inputs.
What are the two major differences between conventional HF and ALE HF communications?
1. ALE lets you call one station in a ALE net selectively without disturbing the rest of the net.
2. The ALE system automatically chooses the best frequency (from a preprogrammed list) for a call
under the conditions at that time.
How many alphanumeric characters are used in most ALE addresses?
Most ALE addresses consist of three alphanumeric characters, even though addresses up to 15 characters long may be used.
What happens if a link attempt is not successful on the first channel selected, or if the channel is busy?
If a link attempt is not successful on the first channel selected, or if the channel is busy, alternative channels are selected automatically.
What is an individual call?
The individual call (station-to-station call) is intended to establish a two-way communication link between two ALE stations on a single, automatically selected channel.
Differentiate between a group call and a net call?
Unlike net calls, which require prior coordination by a network manager, group calls let you contact a group of stations when you know only the self address and scan list.
Define the term “sounding.”
The process of transmitting a signal on a frequency used by other stations to determine that channel’s usability.
State the purpose of link quality analysis.
To determine a particular frequency’s signal quality.
What does sounding contain?
They contain station identity information for use by other stations to “rank” this channel among all channels on the scan list.
Describe an AN/PRC–150 Manpack radio?
The AN/PRC–150(C) is an advanced HF radio which operates from 1.6 MHz to 29.9999 MHz using sky wave (USB, LSB, CW, AME) modulations with selectable low (1.0 watt), medium (5.0 watts), and high
(20.0 watts) output power. The AN/PRC–150(C) also operates from 20.0000 MHz to 59.9999 MHz in FM with maximum power of 10.0 watts. Communications can take place with manpack, mobile, and fixed-site
Where are all functions of the radio controlled from?
All functions are controlled from the front panel and KDU, or via a remote control device.
What does the ALE phone call features allow?
The ALE phone call features allow the radio to call and link to an “HF Ground Station” capable of patching voice calls to a Public Service Telephone Network (PSTN) landline or similar communications network.
What common transmission technique does the AN/PRC–150 use?
It uses a common transmission security technique called frequency hopping.
What type of antenna comes with AN/PRC–150 radio?
The OE–505 manpack whip antenna kit provided with the radio is 3.1 meters long and consists of six collapsible sections.
What is required to operate in medium-range communications along with the AN/PRC–150?
The AN/PRC–150 along with an RF–5834H-PA power amplifier can increase power to a 400-watt capability. It operates in applications where medium-range communications are required.
Where are the impedance matching circuits located?
The signal then passes through an impedance matching circuit in A3A5 Antenna Coupler Assembly.