1C853B CDC Vol.1 Self test/URE
List the two main causes of attenuation in optical fibers.
(1) Absorption; (2) Rayleigh scattering.
Name the four steps of PCM.
(1) Band limiting. (2) Sampling. (3) Quantizing. (4) Encoding.
What are the three ILS categories?
(1) Category I ILS provides acceptable guidance information from the point where the pilot intercepts the ILS to the point where the localizer course line intersects the glide path at a height of 100 ft. above the horizontal plane containing the runway threshold. (2) Category II requires that the pilot must be able to follow the ILS from point of interception to a point where the localizer course line intersects the glide path at a point above the runway threshold. (3) Category III allows for a safe landing from the point of interception to touchdown.
What three components make up the "power of ten" format?
(1) Coefficient. (2) Base. (3) Exponent.
What three types of amplifiers will you most likely encounter in electronic circuitry?
(1) Common collector; (2) Common emitter; (3) Common base.
State the two main precautions when using the vector voltmeter.
(1) Do not exceed the maximum input voltage rating; (2) Handle the probes with care.
The AM‒48 can be used in what three basic configurations?
(1) End-to-end; (2) Loopback; (3) Testing with responders.
When using a wattmeter, what two things are important to be aware of with the elements?
(1) Ensure the plug-in elements are selected based on the proper frequency and power to be measured; (2) Keep the arrows on the plug-in elements flow according to the traveling RF waves; otherwise, the RF waves traveling in the opposite direction of the arrow cancel each other out.
State four disadvantages of using NiCad batteries.
(1) Explosion hazard; (2) Dendrites may develop causing internal short circuits and premature battery failure; (3) Environmental consequences for disposing the batteries; (4) Recharging problems called the "lazy battery effect
Name six parameters a spectrum analyzer can measure.
(1) FM; (2) AM; (3) Pulsed RF; (4) Frequency drift during system warm-up; (5) Long- and short-term frequency stability; (6) Parameters such as subcarrier oscillator outputs and complex signals.
Briefly describe the three fiber classifications.
(1) Multimode step-index: This fiber has a core diameter of 30 to over 800 μm with a constant index of refraction, and a step change in index at the cladding boundary. It allows many modes of light to travel; (2) Single-mode step-index: Small core diameter of 2 to 8 μm helps eliminate dispersion. It propagates one mode efficiently; (3) Multimode graded-index: Has a core diameter of 50 to 125 μm. The core has numerous concentric layers of glass that decrease in refractive index as they go away from the center.
Name the three UPS topologies.
(1) Passive standby; (2) Line interactive; (3) Double conversion
What four advantages do integrated circuits have over conventional wired circuits of discrete components?
(1) Possible improvement in circuit performance; (2) Drastic reduction in size and weight; (3) Large increase in reliability; (4) Lower cost.
What are the five types of power line faults?
(1) Sags; (2) Blackouts; (3) Spikes; (4) Surges; (5) Noise.
List the four basic facts that we must consider in understanding light wave propagation.
(1) The normal (imaginary line perpendicular to the interface of the two materials); (2) The angle of incidence (between the normal and the incident ray); (3) The angle of refraction (between the refracted ray and the normal in the second material); (4) The angle of reflection (between the reflected ray and the normal in the first material)
List the three major types of buffering designs.
(1) Tight buffer tube; (2) Loose tube; (3) Ribbon.
List the three main properties of a parallel circuit.
(1) Total voltage is equal to each of the branch voltages; (2) Total current is the sum of each of the branch currents; (3) Total resistance is always smaller than the smallest branch resistance.
List the three conditions for the servo system.
(1) Tuning up (2) Tuned (3) Tuning down.
State three characteristics that affect radiation pattern of the AN/TPS-75 radar.
(1) Unevenness of the ground surface; (2) Obstacles; (3) Antenna height.
List three applications for the RF generator.
(1) Verifying transmission within designated frequency ranges by comparing transmitter outputs with known radio frequencies; (2) Aligning telemetry receivers by injecting the system with range-standard modulated RF; (3) Check transmission lines and antenna systems for proper operation.
Name the three oscilloscope axes and what information they represent.
(1) Voltage information on the vertical, or Y, axis (up-down); (2) Time information on the horizontal, or X, axis (left-right); (3) Depth information on the Z axis represented by variations in intensity (in-out).
When using the Fluke 8025A multimeter, what is the input direct current (DC) voltage range that can be measured when the function selector is in the DC volts (V) position?
-1000 to +1000.
When an aircraft is on the correct GS, what is the difference between the two modulation depths?
0
What is the binary coded decimal (BCD) equivalent of the binary number 1011?
0001 0001.
Convert the decimal number 13 to BCD.
0001 0011 (BCD)
All matter, depending on their ability to conduct electricity, may be placed into what three categories?
1) Conductors; (2) Semiconductors; (3) Insulators.
Microwave tubes overcome what four problems so they can be used as high power, high frequency oscillators, and amplifiers?
1) RF radiation losses in external circuitry; (2) Inter-electrode capacitance; (3) Electron transit time; (4) Lead inductance.
What is the wavelength if the frequency is changed from 150 megahertz (MHz) to 250 MHz?
1.2 Meters
If the calculation in question 4 was measuring W, how would you display the answer using a metric prefix?
1.9 megawatts.
Perform this power of ten calculation and answer in scientific notation: (7 x 105) + (1.2 x 106).
1.9 x 10to the power of 6.
How many seconds maximum does it take the AN/GRC-171/211 transceiver to tune?
10
When measuring high noise figures with a noise figure meter, at what decibel (dB) level does the result become very inaccurate?
10
What is the maximum separation distance between the AN/TPN-19 operations and radar shelters?
10 miles.
What is the power ratio the bel represents between two sounds?
10 to 1, or 10:1.
Communications facilities require what reading on their system grounds?
10 Ω or less.
In what AN/GRT−21/22 transmitter transmit mode should you connect the antenna to K1J3?
10-watt (W).
Before measuring a signal with the oscilloscope and the source voltage is totally unknown, it is wise to start with a divider probe rated at
100:1.
Convert the decimal number 12 to binary.
1100
What is the binary equivalent of the decimal number 7?
111
What is the frequency range of the AN/GRT-21?
116.000 and 149.975 MHz.
The radio frequency (RF) power output of the CM-350 transmitter is
12 to 35 watts (W).
Both CM-300 series receivers can operate on
120 V AC or 24 V DC.
How many different pieces of test equipment does a communication service monitor (CSM) have combined in one package?
16
If a transmission line has a perfect impedance match, what would the VSWR be?
1:1
How many functions is the CSM capable of performing?
20
What is the power output of the AN/GRC-171?
20 W.
If the modulating audio signal is 10 kilohertz (kHz) wide, what is the bandwidth (BW) of the transmitted amplitude modulated signal?
20kHz
What is the frequency range of the AN/GRT-22?
225.000 and 399.975 MHz.
The frequency range of the AN/GRT−22 transmitter, in megahertz (MHz), is
225.000 to 399.975.
When using the checksum method of error detection, what binary number is used to divide the sum of all the characters in order to derive the checksum?
255
The binary makeup for data word 5 is 0 0101 0101 1001 10. What frequency does this represent?
255.950 MHz.D
What type of signal does the noise figure meter generate to drive a noise source?
28 VDC pulse signal.
If a receiver has an IF of 10 MHz and the desired signal is 290 MHz, what could the two injection frequencies be?
280 or 300 MHz.
Use Ohm's Law to calculate the current of a basic series circuit if the resistance is 10 ohms and the voltage is 20 V.
2A
What is the modulation index of a 5 kilohertz (kHz) modulating signal that has enough peak voltage to cause a deviation of 15 kHz?
3.0
What is the maximum number of users for the MIL-STD-1553 system?
32
How many channels does the CU-547/GR antenna coupler support?
4
If a 10 W signal "A" is 3 dB stronger than signal "B", what is the power of signal "B"?
5 W.
The LPA amplifies the transmitter signal to how many watts?
50 W.
At what frequency is AC generated in the United States?
60 hertz.
What scientific notation is the correct way to express the number 764,500?
7.645x10^5
Express the number 7,750,000,000,000,000 in scientific notation.
7.75 x 10to the 15th power
What is the frequency range of infrared light?
750 to 1,500 nm.
If the signal in figure 2-3C, has an Emax of 50 mVrms and an Emin of 5 mVrms, what is its % mod?
81.8 percent.
What is the transmit duty cycle for the AN/GRC-171 transceiver?
9 minutes transmit, 1 minute receive.
How effective is CRC at detecting errors in most applications?
99 percent in most applications
If the source voltage is totally unknown, what probe should you use?
A 100:1 divider probe to reduce the possibility of damaging the probe.
What can you use to match a 50-Ω cable to a 600-Ω antenna?
A balun
Describe electromagnetic induction.
A changing magnetic field produces voltage in a conductor. If a conductor lies in a magnetic field, and either the field or conductor moves, a voltage is induced in the conductor.
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 is numerical aperture?
A fiber's inherent light-gathering capability.
What is the relationship between modulation index and sideband power?
A higher modulation index means more power in the sidebands. It is even possible to have all the power in the sidebands and none in the carrier. At this point, any further increase in modulation would start taking power from the sidebands and placing it back in the carrier resulting in a redistribution of power.
What is a mode?
A mathematical and physical concept describing the propagation of electromagnetic waves, but for our purpose it is simply a path that light can take in traveling down a fiber.
Define space modulation.
A modulation technique in which the phases and powers of the two individual signals mix within airspace, rather than in a modulator.
What happens when you connect the antenna directly to the mixer?
A part of the oscillator signal might be radiated into space.
What is a significant sideband?
A sideband that contains at least 1 percent of the total transmitted power.
How do we define fiber optics?
A technology in which light is transmitted along the inside of a thin, flexible glass or plastic fiber.
What is the most common use of fiber optics?
A transmission link connecting two electronic devices or circuits.
What should objects in proximity to the TACAN antenna be under?
A truncated cone.
In what transmitter module is the RF generated?
A8 oscillator synthesizer.
What type of circuit has voltage that forces electrons to flow first in one direction, then in the opposite direction, alternating very quickly?
AC circuit.
What test equipment tests the integrity and quality of 2-wire or 4-wire voice and data transmission lines by sending selected analog signals and measuring standard parameters of the received signals?
AM‒48, transmission test set.
Between the AN/GRC-171 and AN/GRC-211, which transceiver has a continuous transmit duty cycle?
AN/GRC-211.
What Precision Approach Radar (PAR) test set allows you to test radar power, frequency, pulse repetition frequency (PRF), range tracking capabilities, receiver bandwidth, and minimum discernible signal?
AN/UPM-145.
Which logic gate requires all inputs to be HIGH in order for the output to be HIGH?
AND gate
What versatile UHF antenna has removable radiators and is omnidirectional?
AT-197/GR.
Who do you communicate with during the communication portion of the airfield driving test?
ATCT.
What two types of power does the power meter measure?
Absolute or relative power.
To what can we attribute fiber-to-fiber connection power losses?
Acceptance cone/ejection cone mismatches, fiber core diameter mismatches, connector insertion loss, and intrinsic fiber loss.
In the A4 module, what do you optimally adjust R41 for when there is no input signal?
Adjust R41 to balance out the transistor bias so that the meter reads zero when there is no signal in.
What is the output RF power range for the CM‒350 (V2) VDT?
Adjustable from below 12 W up to 35 W.
In a schematic diagram, how is current flow always portrayed on a transistor when it is forward biased?
Against the arrow.
When a transistor is forward biased, how does the current flow in relation to the arrow on the schematic diagram?
Against the arrow.
What is used as a dielectric in waveguides?
Air
What test equipment enables technicians to communicate with telephone switching equipment through the use of pulse, dual tone multi-frequency (DTMF), and multi-frequency (MF) dialing?
Ameritec Model (AM)‒48 transmission test set.
The time required for a capacitor to charge depends on what two things?
Amount of resistance through which the charging current flows and the size of the capacitor
What part of the modulating signal controls the amount of phase shift in PM?
Amplitude
What does the vector voltmeter measure?
Amplitude and phase of two RF voltages of the same frequency.
What is the process of heterodyning an intelligence (audio) signal with a radio frequency (RF) carrier to produce a new signal?
Amplitude modulation (AM).
What is normally connected to the primary winding of a transformer to induce voltage into the secondary winding?
An AC signal.
Define Antenna Gain
An increase in radiating effectiveness of an antenna system over some standard (usually an isotropic antenna).
What type of line fault can be found by putting a tone on one end and checking for continuity at the distant end?
An open circuit.
What is an image frequency?
An undesired signal that, when mixed in the mixer, produces the correct IF.
What does the GS represent for the pilot?
An ~3 degrees glide path to the runway threshold.
What multimeter function shows a 31-segment bar graph, which indicates the absolute value of the input?
Analog bar graph.
When considering light wave propagation, what is the name of the angle between the normal in the first material and the ray that is bounced back in the first material?
Angle of reflection.
What component allows two receivers to connect to one antenna?
Antenna coupler.
Explain the term load.
Any device through which an electrical current flows and which changes this electrical energy into a more useful form.
How does an SCR turn on?
Applying a small positive potential to the gate terminal of the SCR forward biases the middle junction and turns the SCR on.
What happens to the audio in the AN/GRC-171/211 transceiver when the squelch sample is greater than the front panel squelch reference?
Audio is heard at the speaker.
What provides the legal audio recording capability between air traffic controllers, pilots, and ground-based entities?
Audio recorder.
What equipment produces stable AF signals used for testing audio equipment?
Audio signal generators.
List the three intelligence inputs used to modulate the carrier.
Audio, mic, and the data inputs.
In a generator, what allows smooth and immediate transfer of electrical current between multiple sources and the load?
Automatic transfer switch
What feature of the 436A power meter is ideal for monitoring fast changes while adjusting peak transmitter output?
Auxiliary meter.
On the vector voltmeter, the phase indicated on the meter represents the relative phase between what two signals?
B channel with respect to the A channel.
In LRC, what transmitted character does the receiver use to determine if a transmission was error free?
BBC
When testing a fiber optic (FO) cable, what is the energy that travels back toward the optical source called?
Backscatter.
What is the first step in the pulse code modulation (PCM) process?
Band-limiting the analog signal.
The direct flow of current from the negative battery post to the positive post is a representation of what kind of circuit?
Basic DC circuit.
Why is there very little radiation loss in a rigid coaxial cable?
Because the energy is confined between the two conductors.
Why does the UHF multiplier contain one more stage of amplification than the VHF version
Because the fourth harmonic is weaker than the second.
What happens to light when it passes from a higher-index material to a lower one?
Bent away from the normal.
What range of input voltages can you measure when using the Fluke 8025A's AC volts function?
Between 0 and 1,000 VAC.
What range of input voltages can you measure when using the Fluke 8025A's DC volts function?
Between −1,000 and +1,000 VDC.
What is the simplest numbering system used in digital circuitry?
Binary (or base 2) system.
How does synchronous transmission reduce the overhead costs of data transmission?
Blocks many characters together for transmission.
What test equipment allows individual access to all signal conductors in a 25-wire Recommended Standard (RS)-232 connector?
Breakout box.
How do you determine the modulation index in FM?
By dividing the amount of frequency deviation by the frequency of the modulating signal.
How does the receiving device determine whether it has received a correct character?
By summing the 1 bits. If the character arrives with an even number of bits, the device assumes that it has received a correct character.
How are optical fibers generally classified?
By the number of modes and the core's refractive index profile.
How can we reduce Fresnel losses in a fiber?
By using index-matching fluids.
Besides accessing front panel controls, what other way can you select the operating frequency, make adjustments, and monitor various transmitter functions on CM‒300/350 transmitters?
By using the front panel controls or an MDT device.
What is the purpose of the E/L relay when using an LPA?
Bypass a defective LPA or bypass the LPA in the event of AC power failure or excessive VSWR.
What should you do if an AN/GRT−21/22 transmitter's voltage standing wave ratio (VSWR) exceeds 3:1?
Bypass the linear power amplifier (LPA).
How does the CRC method of error detection determine the dividend when computing the BCC?
CRC treats the binary ones and zeros in the frame address, control, and information fields as one long binary number.
What analyzer provides the capabilities of 16 different pieces of test equipment in one convenient package?
CSM
What type of circuit component stores an electrical charge?
Capacitor.
Which is not a type of rechargeable, secondary cell battery?
Carbon Zinc.
What component of a fiber optic (FO) cable provides the reflective surface that allows light to propagate?
Cladding.
What wave-shaping circuit ties down the upper or lower extremity of a waveform to a fixed direct current (DC) potential?
Clamping
What does the low pass filter section use to prevent over modulation when using the data input?
Clipper circuit.
What is electrical length?
Comparison of physical length and wavelength expressed in number of wavelengths.
Which is not a waveform produced by a function generator?
Compound waveform.
In the audio section of the AN/GRC-171/211 transceiver, what component keeps the modulation percentage constant?
Compression amplifier.
What component keeps the modulation percentage constant?
Compression amplifier.
What kind of material must be used in the construction of waveguides?
Conductive material.
What parameters can a multimeter measure?
Continuity, resistance, current, voltage, diode, and temperature checks.
A resistor is used in a circuit to
Control current flow
Define sampling
Converting a continuous time signal into a discrete time signal.
What does a power sensor do?
Converts RF energy into a linear DC voltage that can be used by the power meter.
The large surface area of a waveguide greatly reduces what type of loss that is common in two-wire and coaxial lines?
Copper loss (I^2R).
What is the most useful way to classify fiber optic (FO) cable?
Core's refractive index profile and number of modes.
What are the components of a typical fiber optic cable?
Core, cladding, and protective coating (buffer).
What is the most selective filter in the system, determining overall selectivity?
Crystal filter.
What primary condition must magnetic lines of force meet in order to exist?
Current flow in a conductor.
In 1819, Hans Christian Oersted discovered the strength of a magnetic field can be changed by varying what characteristic?
Current through a conductor.
What is the biggest limitation for space-wave communications?
Curvature of the Earth.
What connectors are almost universally used on the RS-232 data bus?
DB-25
What type of signals can you measure on the PIR?
DDM, percent of modulation, RF, AF, THD, and perform SA.
Name two safety precautions to observe when working with fiber optics.
DO NOT look into a laser beam, severe eye injury or blindness could result; (2) Always wear goggles when working with the fibers to protect against flying fragments of silica, especially if you clean the fibers.
What logarithmic expression do we use to specify the ratio of power loss in fiber optic (FO) cables?
Decibels-per-kilometer (dB/km).
What happens to electrical length as signal frequency decreases?
Decreases.
The formula to find the modulating index is
Deviation divided by frequency of modulation.
When using the Fluke 8025A multimeter for diode checks, what does it mean when you get an "OL" indication when you place the leads across the diode and also when the leads are reversed?
Diode is considered non-operational.
What type of antennas is used more often today due to their smaller size, cheaper costs, and technological advancements?
Dipole collinear array antennas.
How is light affected in a cable that has a large numerical aperture?
Dispersion is increased.
What UPS topology provides the highest level of protection?
Double conversion.
What type of multiplier does the AN/GRT−21 transmitter have?
Doubler.
The A9 module multiplies the signal by what factor in the VHF transmitter?
Doubles the signal.
When bench-checking a transmitter, what test equipment should you use to absorb any transmitted radio frequency (RF) signals?
Dummy load.
When is the carrier at its rest frequency in PM?
During the constant amplitude part of the modulating frequency.
Describe the effect the positive and negative alterations of a modulating signal have on the phase of the carrier in PM.
During the positive alternation of the modulating signal, the phase of the carrier lags behind the unmodulated carrier. During the negative alternation, it leads the unmodulated carrier.
What test equipment would you use to verify if a ground rod is effective and conduct stray voltages to the ground?
Earth ground tester.
Which statement describes an advantage of using fiber optic (FO) cables?
Electromagnetic fields do not affect fiber optic cables.
What test equipment measures frequency by totaling (or counting) the number of input cycles, or events, over a precise period of time?
Electronic counter.
What is a disturbance generated by an external source that affects AM electrical circuits by electromagnetic induction, electrostatic coupling, or conduction?
Emi/RFI
Optical fibers are normally composed of what materials?
Entirely of glass or silica, plastic-clad silica, or all plastic.
Who conducts flight check inspections?
FAA personnel with assistance from RAWS personnel.
What test equipment is essentially an upgraded, portable spectrum analyzer?
Field Fox.
Converts pulsating DC to a purer, more desirable form of DC voltage.
Filter
How many channels does the CU-547/GR support?
Four.
What is another name for chassis ground and what is its purpose?
Frame ground. It ensures the chassis of two devices are at the same ground potential to prevent electrical shock to the user.
What part of the modulating signal controls the rate of phase shift?
Frequency
What term refers to a transmitter's ability to maintain a constant output carrier frequency?
Frequency accuracy.
Where do FM sidebands get their power?
From the unmodulated carrier.
What is the primary purpose of an oscillator?
Generate a given waveform at a constant peak amplitude and specific frequency and to maintain this waveform within certain limits of amplitude and frequency.
State the purpose of a network/protocol analyzer.
Generates, monitors, and captures data traffic moving across a network connection.
What input coupling position lets you set a zero-volts reference level on the CRT screen without disturbing the input signal connection?
Ground (GND) position.
What is the output of the PTT keyer, regardless of the input?
Ground.
One of the advantages of fiber optics is high bandwidth. What is bandwidth?
High bandwidth, the information-carrying capacity of a carrier wave.
What type of antennas is less likely to pick up other interference?
Horizontal antennas.
What oscilloscope axis produces the trace on the display screen?
Horizontal, or X, axis.
What receiver module provides most of the receiver's amplification?
IF amplifier and detector A6.
What receiver circuit has tuned circuits, fixed at a definite resonant frequency?
IF amplifier.
What component determines the overall receiver selectivity?
IF filter.
What navigational systems do you use the PIR for?
ILS localizer and glide slope, VOR, and marker beacon equipment.
What does Snell's law state?
If a ray of light enters a junction of two media of different refractive indices beyond the critical angle, the light is totally internally reflected.
What is a measure of the combined opposing forces to an alternating electric current?
Impedance
How do we measure dispersion?
In (ns/km).
What is the difference between half-duplex and full-duplex communications?
In a half-duplex channel, data may travel in both directions but only one direction at a time. In a full-duplex channel, data may travel in both directions simultaneously.
How do we express the amount of power in a fiber optic link?
In microwatts or milliwatts.
In what section does most of the superheterodyne receiver amplification take place?
In the IF section.
When are light guns used?
In the event of a radio failure.
If the ALC voltage decreased, what would the RF output of the predriver/ALC attenuator do?
Increase.
What effect does nuclear radiation have on fiber optic cables?
Increased attenuation caused by absorption and scattering
Which is not a conventional problem that microwave tubes overcome in order to be used in high power, high frequency oscillators and amplifiers?
Inter-cathode resistance
Which receiver component determines the overall selectivity?
Intermediate frequency (IF) filter.
When in the transceiver configuration, what component provides the transmit and receive switching?
Internal ATR switch.
What is the purpose of an RMS voltmeter?
It calculates the equivalent DC current value of an AC waveform.
Describe isochronous data transfer.
It combines the features of an asynchronous and synchronous data transfer system.
What happens when a fiber's bending radius is exceeded?
It experiences macrobends or microbends.
Describe a nonresonant transmission line.
It is a line that has no reflected waves.
Describe the fiber core.
It is often made from a solid section of ultra pure, ultra transparent silicon dioxide or fused quartz (glass), but may also be made of plastic
What is spectral attenuation?
It is related to light wavelengths and requires careful balancing of light sources and fibers.
What is a standing wave?
It is the vector sum of the forward and reflected waves.
Why are communications over fiber optic cables highly secure?
It is virtually impossible to tap a fiber optic cable unnoticed because the light-carrying part of the core is so affected by the tap that it is easily detected. Since fiber does not radiate energy, other eavesdropping techniques are useless.
Define "percent of modulation."
It refers to the amount of effect or change that the intelligence has on the carrier.
What signal information can you gather from an oscilloscope's graphic display on the CRT?
It shows you an actual graphing of the signal's amplitude as it relates to time (amplitude vs time). With this display you can tell its wave shape, its frequency, and its amplitude and whether the signal is relatively pure.
What determines ZO of a transmission line?
Its series inductance and capacitance.
Explain the difference in timing between key 1 and key 2.
Key 1 is FASR, while key 2 is SAFR. Fast attack means that key 1 goes low quickly when keyed; slow attack means that key 2 goes low after a small (milliseconds) delay. Fast release means that key 2 goes high quickly when unkeyed; slow release means that key 1 goes low after a small (milliseconds) delay.
What types of audio do the CM‒300 transmitter family support?
Legacy analog audio and VoIP digital audio.
Why are coaxial lines more efficient at microwave frequencies than two-wire transmission lines?
Less radiation loss because fields are completely confined by the conductors
What type of wave-shaping circuit prevents some part of a waveform from exceeding a specified value?
Limiter.
How does dispersion affect the bandwidth?
Limits it.
What action develops the BCD information that the radio uses to tune the filter to a desired frequency?
Local frequency select thumbwheels.
What ILS component provides the lateral component to for the runway centerline?
Localizer
What system is the MBTS primarily used for?
MSSR.
What is the most commonly used means for producing or using electricity?
Magnetism.
What does AGC do?
Maintains a constant audio output with a varying RF input.
What is the metric prefix for the decimal number 1,000,000?
Mega.
What frequency range are waveguides principally used?
Microwave range.
What data bus was originally developed for military avionics applications?
Military Standard (MIL-STD)-1553
What applications were the MIL-STD-1553 data bus was specifically designed for?
Military avionics applications.
What metric prefix is used to describe the decimal number .001?
Milli
The length of the AN/TPS-75 interconnecting waveguide and the bend limits of the flex waveguide limit the distance between the antenna pallet and equipment shelter to what distance range?
Minimum of 7 ft. to a maximum of 21 ft.
What causes each of the two main types of dispersion?
Modal dispersion is caused by the different paths of light in various modes. Material dispersion is caused from different velocities of different wavelengths.
What is the main purpose of the breakout box?
Monitor and access multiple conductors; including the conductors of EIA RS-232 and ITU V.24 interfaces
Define the term current
Movement of free electrons through a conductor
What type of fiber has a core diameter of 50-125 micrometers (μm) and consists of numerous concentric layers of glass, something like the annular rings of a tree, configured to reduce dispersion?
Multimode graded-index.
Which fiber classification has the highest dispersion factor?
Multimode step-index.
When siting a localizer, what is the maximum height of surface roughness for area "A"?
Must not exceed ±0.5 ft.
Which logic gate only outputs a HIGH when all inputs are LOW?
NOR gate
What type of oscillator generates complex waveforms to include square, trigger, and sawtooth waves?
Non-sinusoidal.
In PM, what effect does the change in carrier frequency have?
None. The frequency change in PM is incidental
What modulation characteristic must be present for heterodyning to take place?
Nonlinearity.
What does VRC check each incoming character for?
Odd or even parity.
What type of antenna is best used for communicating with aircraft in all directions around a location?
Omnidirectional.
What type of antenna receives well in all directions but also allows interference from all directions?
Omnidirectional.
Describe the ideal location for RAWS equipment siting.
On flat terrain away from metallic fences, overhead power and telephone lines, heavily wooded areas, hangars, and other obstructions for several thousand ft. in all directions.
Where are ILS indications displayed in an aircraft?
On the attitude indicator.
Where should you locate the VOR system?
On the highest suitable ground with the surrounding terrain level or gradually sloping away from the site.
With ATM, what is the length of each transmission unit?
One character in length.
In a simplex channel, what direction does data travel?
One direction.
How is a loose-tube buffer formed?
Optical fibers are usually coated with a thin layer of acrylate (250 μm diameter) and then several fibers are placed in a hard plastic tube with an inside diameter several times larger than the diameter of the fiber.
Compare attenuation in fiber optics to attenuation in metallic cables.
Optical fibers have less attenuation (power loss) than metallic cables.
How does a fiber reach equilibrium-mode distribution?
Over distance.
What part of the pulse train is varied using PAM, PWM, and PPM?
PAM = amplitude, PWM = width or duration, PPM = position.
Which is not an uninterruptible power supply (UPS) topology?
Passive conversion.
What test equipment allows CW power measurements along with the ability to make precise peak power measurements at any point on a pulsed waveform?
Peak power meter.
What is the primary lower-frequency limitation of waveguides?
Physical size. The width of the waveguide must be approximately half wavelength of the frequency transmitted.
Explain what digital multimeter readings you should get when testing a good diode.
Placing the leads across a "good" diode produces an "OL" (open) on the display in one direction while reversing the leads produces a continuous audible tone indicating a short.
Which electrical term is measured in watts (W)?
Power
What term describes the narrowing down of input frequencies for a receiver, with tuned circuits selecting a band of frequencies around the desired signal?
Pre-selection.
What term describes the process of tuned circuits selecting a band of receiver frequencies around a desired signal?
Pre-selection.
Which module develops the AGC and squelch functions?
Preamplifier, AF/AGC-squelch A3.
What are the two battery categories?
Primary and secondary cells.
Which battery category includes the common disposable flashlight battery?
Primary.
Which subatomic particles are contained in the nucleus of an atom?
Protons and neutrons
What is the main purpose of the AN/TPM-32 Video Signal Processor test set?
Provides bench testing and online monitoring of the Video Signal Processor CP-1045/T of the AN/TPX‒ 42A Interrogator Set.
What is the purpose of the fiber cladding around the core? What material is it made of?
Provides the reflective surface that allows light to propagate along the core to the distant end. It is a solid section of transparent glass or plastic with a much lower density than the core
In the UHF A2 module, the quadrupler multiplies the oscillator frequency to what level?
Quadruples it up to the injection frequency.
The A9 module multiplies the signal by what factor in the UHF transmitter?
Quadruples the signal.
What type of equipment permits complete RF and IF performance tests on virtually any type of HF, VHF, or UHF receiver?
RF signal generators.
What PAR parameters can you test with the AN/UPM-145 radar test set?
Radar power, frequency, PRF, range tracking capabilities, receiver bandwidth, and minimum discernible signal.
Which test equipment item would you use to check transmission lines and antenna systems for proper operation?
Radio frequency (RF) generator.
Describe refractive index
Ratio of the speed of light in a vacuum to its speed in a given medium.
When using forward error control, at which end of the transmission link are errors corrected?
Receiving end.
Explain antenna reciprocity.
Reciprocity is the ability of an antenna to both receive and transmit equally well.
Converts the AC input signal to a pulsating DC.
Rectifier
What is an advantage of synchronous transmission over asynchronous transmission?
Reduces the overhead costs of data transmission.
Describe reflection.
Reflection is the bouncing back of light from an object.
What do we call the phenomenon that occurs when light bends while passing through material of different density?
Refraction
What organization can provide remote maintenance and system oversight for navigational aids?
Regional Maintenance Center.
Maintains the output of the power supply at a constant level in spite of large changes in load current or input line voltages.
Regulator
What power supply circuit senses changes in output voltages and compensates for the changes, usually within plus or minus (±) 0.1 percent?
Regulator.
What two components utilize electromagnetic principles to perform mechanical actions for a circuit?
Relays and solenoids
What is the opposition a device or material offers to the movement of electrons?
Resistance.
What are some of the types of transmission line loss?
Resistive, skin effect, radiation, induction, capacitive, and leakage.
When siting weather equipment, when are midfield sensor groups necessary?
Runway is longer than 8,000 feet (ft.) or the location must meet Category II criteria.
What visual aid gives the technician a "picture" of circuit components?
Schematic diagram.
What type of oscilloscope probe should you use to keep resistive loading errors below one percent?
Select a probe/scope combination that has a Rin at least 100 times greater than the source impedance.
What are two results of over modulation?
Severe distortion and increased bandwidth of an AM signal.
What electrical malfunction is caused by a loss of resistance in a component?
Short
Optic fibers are made of dielectric materials. How are fiber optic cables affected by electromagnetic interference?
Since fiber optic cable does not radiate or absorb energy through its outer jacket, it is immune to this type of interference.
What are some of the most common waveforms produced by the function generator?
Sine wave, square wave, triangular wave and sawtooth shapes.
Which fiber type is very efficient for long-distance and very high-speed applications, but is hard to work with?
Single mode step-index.
What determines the frequency, bandwidth, and power-handling capability of a waveguide probe?
Size and shape of the probe
State two things that happen to a diode's depletion region when it is forward biased.
Size of the depletion region will be reduced and its resistance will also decrease.
What causes the current-carrying area at the center conductor of a coaxial line to be restricted to a small layer at the surface?
Skin effect
Loose or inefficient coupling of energy into or out of a waveguide can be accomplished by the use of what method?
Slots or apertures
Which circuit cuts off a receiver's audio output if the radio frequency (RF) signal is too weak and allows the signal to reproduce when the RF signal strength meets or exceeds a predetermined level?
Squelch.
Which instruction word monitors "faults" in the remote units?
Status
What type of transformer produces a smaller voltage at the secondary winding than the primary winding?
Step down transformer
What is isochronous data transfer commonly used for?
Streaming video.
How does synchronous transmission differ from asynchronous transmission?
Synchronous transmissions block many characters together for transmission.
What oscilloscope function controls how fast the trace is drawn across the screen?
TIM/DIV control.
What does sidetone tell an operator?
Tells the operator that the radio is modulating a carrier that goes to the antenna jack.
Which module develops the APC voltage?
The A6 control radio frequency/modulator.
To prevent interferences with other FM stations, what agency establishes limits on the maximum amount of deviation in FM?
The FCC
Explain the basic principle of how an OTDR works.
The OTDR is an oscilloscope with a built-in laser that sends a light pulse into the end of a fiber and measures the loss of light as it is reflected back to the source.
What is the injection frequency for UHF and VHF?
The UHF injection frequency is 30 MHz below the operating frequency and the VHF injection frequency is 30 MHz above the operating frequency.
Explain mutual induction.
The action in which a change of current in one coil (or circuit) induces a voltage into another coil (or circuit).
What determines the amount of deviation of a FM carrier?
The amplitude of the modulating signal.
Describe the critical angle.
The angle of incidence that causes the angle of refraction to equal 90 degrees.
In AM, what is the relation between the bandwidth required to transmit the signal and the frequency of the modulating signal?
The bandwidth required is two times the modulating signal frequency
What part of the AM signal does not fluctuate in amplitude by the modulating signal?
The carrier.
The refractive index is a relationship between what elements of a fiber?
The core's refractive index and the cladding's refractive index.
What are the causes of major power loss in a flexible coaxial cable?
The dielectric and skin effect.
Define "wavelength."
The distance in space occupied by one cycle of a radio wave at any given instant
What happens to the H-lines between the conductors of a coil when the conductors are close together?
The fields cancel between the sections.
Define the term voltage.
The force or electrical energy required to move electrons from one place to another.
What does "cutoff frequency" refer to when you talk about transmission lines?
The frequency at which the value of XL and XC are such that the signal is developed across the series inductance and shunted by the capacitance and, thus, not passed along the line.
What characteristic of the carrier wave does the energy possessed by the photon determine?
The frequency.
What interaction causes energy to travel down a waveguide?
The interaction of the magnetic (H-field) and electric fields (E-field) causes the energy to travel through the waveguide.
What is the difference between a mixer and a convertor?
The mixer requires two input signals: the radio frequency and the injection frequency. A converter has its own self-contained oscillator and requires only one input signal, the radio frequency.
The electron theory assumes that all electrical and electronic effects are due to what phenomenon?
The movement of electrons from one place to another.
What operations can be done from the receiver front panel or MDT device?
The operator can select the operating frequency, make adjustments, and monitor various receiver functions using the front panel controls or an MDT device.
Find the % mod if a 4 Vpk-pk RF signal is modulated by a 2.5 Vpk-pk audio signal.
The percent of modulation is 62.5 percent, found by dividing 2.5 by 4 and multiplying the result by 100.
Define demodulation
The process of recovering intelligence from the modulated wave
Define multiplexing
The process of transmitting more than one channel of information over a single line.
How does ARQ work?
The receiver automatically sends a retransmitted request to the sender if it finds an error in a received frame.
What is the difference between the A8 modules in the AN/GRC-171 and AN/GRC-211?
The reflectometer (A8A7) is not used in the VHF version of the A8 module.
What is indicated by the number of arrows (closeness of spacing) used to represent an electric field?
The relative strength of the field and how evenly distributed the field is
What are the different remoting requirements to consider when siting the AN/TPN-19?
The shelter may be set up within 10 nmi for 7.5 GHz remoting, or within 4.3 nmi for 15 GHz remoting of the AN/TPN-24 ASR and AN/TPN-25 PAR.
What part of the modulated carrier wave contains the information carrying component?
The sidebands.
What are the primary determinants of a line's capacitance?
The size of the conductors, the space between them, plus the dielectric material.
What is dispersion in a fiber optic cable?
The spreading out of the light in a fiber.
Explain the function of a squelch circuit in a receiver.
The squelch circuit cuts off the receiver's output if the RF signal is too weak and allows the signal to reproduce when the RF signal strength meets or exceeds a predetermined level.
What part of ATM transmission tells the receiving device that a character is coming and that the character has been sent?
The start and stop bits.
How do you calculate the total resistance of a series circuit?
The sum of all the individual resistances in the circuit.
How do you calculate the total current of a parallel circuit?
The sum of the individual branch circuit current values.
What needs to happen in the CM-350 transceiver configuration antenna transfer relay in order to transmit?
The transmitter keys, then the ATR routes the transmit signal to the antenna.
Explain why a modem is useful in communications circuits.
They allow computers to communicate with other computers or computer systems.
Explain dummy load construction and how it dissipates RF.
They are constructed so that RF power is absorbed with minimal reflections and the absorbed energy is converted to heat.
How does the rate of deviation relate to the frequency of the modulating signal?
They are directly proportional.
Which is not a reason why oscilloscope probes are used?
They ensure circuit loading.
What are the main drawbacks of diode detectors?
They provide no power gain and selectivity is affected by loading of the tank, therefore the quality factor of the tank lowers when the diode conducts.
Why are transmitters now designed with the modulation occurring in the amplifier circuits?
This change was driven by the need for better frequency stability as well as by the fact that oscillations would tend to stop in an oscillator when 100 percent modulation was used.
Define "VSWR."
This is a comparison (expressed as a ratio) of the maximum and minimum voltages found along the line.
Explain how the channels of the Transmitter Control C‒10639/G ALOD work in the normal fourchannel configuration.
Three of the four inputs (lockout channels) are mutually exclusive; that is, the first input gains access to the transmitter and disables the remaining two lockout channels as long as the first input remains. The fourth channel is a priority channel, which can immediately override any of the other three channels.
Which method of transmission requires the receiving end to be synchronized with the transmitting commutator?
Time division multiplexing
Name the portable test set that uses radar principles to test copper core-cables and provides a visual display of cable faults.
Time domain reflectometer.
What oscilloscope control adjusts how fast the trace is drawn across the screen?
Time per division (TIM/DIV).
What type of multiplexing separates each channel using a cyclic sequence?
Time-division multiplexing.
Explain why the Field Fox was designed.
To assist in monitoring signals specifically in surveillance and secure communications, radar, electronic warfare, commercial wireless, and any signal from 5 kHz up to 50 GHz.
When using forward error control, what is the receiver's function in error correction?
To compare all copies of the transmitted message, and then reconstruct the message using the good portions of the message copies received.
Why are resistors used in a circuit?
To control current flow in the circuit.
Why was the spectrum analyzer created?
To discriminate between frequencies while still measuring each power level and display information in the frequency domain.
What is the sweep generator's most important function?
To ensure linear beam movement, meaning the beam moves at the same rate from start to finish.
State the main purpose of the band-limiting filter.
To ensure the input to the sampler never exceeds a maximum frequency.
State the two basic purposes of a transistor.
To perform as a switch or amplify a circuit.
When not transmitting, where does the ATR transfer the incoming signals?
To the receiver.
What is the transmitter's function in error correction when using forward error control?
To transmit multiple copies of the same message to the distant end.
What test equipment would you use to find a cable within a huge bundle?
Tone generator and inductive amplifier.
What does a distortion analyzer measure?
Total RMS distortion and gives a ready determination of percentage of distortion.
Steps up or steps down the input line voltage and isolates the power supply from the power line.
Transformer
What AN/GRT−21/22 transmitter component eliminates unwanted harmonics generated in the A10 driver?
Tunable filter, FL2.
What is the maximum tuning time for the AN/GRC-171 and AN/GRC-211?
Tuning the transceivers takes a maximum of (but usually less than) 10 seconds
What are the two most important factors in magnetic field strength around a conductor?
Type of core and the amount of current in the coil.
The amplitude modulated waveform contains what frequencies?
Unmodulated carrier frequency, USB, and LSB.
Name two methods of reducing induction loss.
Using standoff insulators and shielded conductors.
What is the difference in channel spacing between the UHF and VHF CM-300 receivers?
VHF has 25 kHz or 8.33 kHz channel spacing while UHF only has 25 kHz.
What is the difference in channel spacing between the very high frequency (VHF) CM- 300/350 and the ultra high frequency (UHF) CM-300 transmitters?
VHF has a channel spacing of 8.33 or 25 kHz and the UHF channel spacing is 25 kHz only.
CM-300 series receivers support legacy analog audio and
Voice over Internet Protocol (VoIP).
What is an incident wave?
Voltage and current waves as they move from source to load.
What is the phase relationship between forward and reflected voltage waves when the line is terminated in a short?
Voltage is reflected 180 degrees out of phase.
Describe what a discrete RS-232 signal is.
Voltage signals where a voltage is either present or not present.
What is the voltage level at an open termination?
Voltage will be at maximum across an open.
Which is not an acceptable action to take if a communications facility ground testing reveals more than 10 ohms (Ω) resistance?
Watering the soil around the facility.
What is the unit of measurement for power?
Watts (W)
What technology uses different colors of light to combine multiple data streams?
Wave division multiplexing.
What happens to wavelength as a signal's frequency decreases?
Wavelength increases.
What standard reference level was adopted in order to relate the power of a signal?
When 1 mW is used as a reference level, the ratio between the actual power and the 1 mW reference is expressed in dBm.
Explain what a runway incursion is.
When an aircraft, vehicle, or person enters the protected area of a surface designated for the landing and take-off of aircraft without approval from ATCT.
When is an atom considered electrically neutral?
When it contains the same number of positive charges in the nucleus as it has negative charges in its orbits.
At what point do coaxial cables become either impossible or unpredictable to use?
When the distance between the central conductor and the inner sheath of a coaxial cable approaches the dimensions of quarter-wavelength.
When siting weather equipment, when would you need a midfield sensor group?
Where the runway is longer than 8,000 ft. or at a location that must meet Category II criteria.
What electronic component is specifically designed to operate in the reverse bias mode?
Zener diode.
No matter the input keying voltage to the AN/GRC-171/211 transceiver, the output is always
a ground.
Space modulation is commonly referred to as
a. difference in the depth of modulation (DDM).
When a CM-300 series transmitter and receiver are connected to a common antenna, and the antenna transfer relay (ATR) switch position is set to ATR0, the transmit and receive switching is handled by
an internal ATR switch in the transmitter.
An advantage of integrated circuits (IC) is that they
are more reliable.
When using forward error control as a method of error correction, error correction takes place
at the receiving end.
When the modulating signal and carrier signal are combined within a modulator, the output signal contains the
carrier, upper sideband, and lower sideband.
The biggest limitation to space-wave communications is
curvature of the Earth.
What unit of measurement do we use to express fiber optic attenuation?
dB/km.
Because of screening, you need to avoid placing the AN/TPS−75 Radar System in
depressions and valleys.
If the AN/GRT−21/22 transmitter power supply temperature is too high, the thermal detector in the A7 module
develops the keyer inhibit voltage.
A non-rechargeable, primary battery is often referred to as a(n)
dry cell.
If a conductor lies in a magnetic field, and either the field or conductor moves, a voltage is induced in the conductor. This effect is called
electromagnetic induction.
Photon particles are a part of what spectrum?
electromagnetic spectrum
With the alternating current (AC) method, voltage forces electrons to flow
first in one direction, then in the opposite direction, alternating very quickly.
An atom becomes an ion by
gaining or losing electrons in it outer shell.
Diode detectors give
high-fidelity detection for signals of sufficient amplitude
Energy travels through a waveguide because of
interaction of magnetic and electric fields.
A theoretically perfect radiator (antenna) that radiates equally well in all directions is
isotropic.
The tone generator applies an audio tone to a pair or cable and the inductive amplifier is used to
listen for the generated tone at the other end.
Reducing modulation to less than 100 percent results in
no reduction in carrier power.
One disadvantage to using fiber optic (FO) cables is that
nuclear radiation can darken the optical fiber and cause signal loss.
Which atomic shell has the most energy?
outer shell
The oscillator output in a frequency modulation (FM) modulator increases in frequency with each
positive half cycle of the modulating signal.
Three devices used to inject or remove energy from waveguides are known as
probes, loops, and slots.
In phase modulation, the rate of phase shift is
proportional to the frequency of the modulating signal.
What is the purpose of the tune/operate switch?
protect the tunable filter during tuning operation
A Zener diode is specifically designed to operate in
reverse bias mode.
The number of pulses in the direct current (DC) output of a bridge rectifier is called the
ripple frequency
When an aircraft, vehicle, or person enters the protected area of a surface designated for the landing and take-off of aircraft without approval from Air Traffic Control Tower (ATCT), it is called a
runway incursion.
The two basic purposes of a transistor are either to perform as a
switch or amplify a circuit.
For greatest wattmeter accuracy, select the power element(s) having
the lowest possible power range that will not result in over-ranging.
On a transmission line with an open termination, the wave is reflected back to the source and
there would be significant signal loss.
The decibel (dB) does not (in itself) indicate power; instead, it indicates a ratio or comparison between
two power levels.
The image frequency is a(n)
undesired signal that, when mixed in the mixer, produces the correct IF.
The automatic gain control (AGC) voltage maintains a constant audio output with a
varying RF input.
A capacitor will oppose a change in
voltage and store energy in an electrostatic field.
What is the unit of measure for electrical length?
wavelengths
What is the frequency accuracy for the AN/GRR-23 and AN/GRR-24 receivers?
±0.0005 percent after 5-minute warm-up.
When selecting a site for the Instrument Landing System (ILS), what is the localizer maximum height tolerance, in feet, for surface roughness in area "A"?
±0.5.
