Volume 3. General Comm/nav Systems Theory (Part 1)

Front 1

401. The Earth and its geographic coordinates
On what axis does the Earth rotate?

Back 1

Polar axis.

Front 2

401. The Earth and its geographic coordinates
What do you call the extremities of the polar axis?

Back 2

The poles.

Front 3

401. The Earth and its geographic coordinates
What do you call the plane perpendicular to the polar axis and equal distance from the poles?

Back 3

The equator.

Front 4

401. The Earth and its geographic coordinates
What’s a great circle?

Back 4

A great circle is formed on the surface of the Earth by any plane that passes through the center of the Earth
and divides it into two equal parts.

Front 5

401. The Earth and its geographic coordinates
What is special about a course plotted between two points along a great circle?

Back 5

It’s the shortest route between them.

Front 6

401. The Earth and its geographic coordinates
What are the two fixed reference points used in the Earth’s geographic coordinate system?

Back 6

The equator and Greenwich meridian.

Front 7

401. The Earth and its geographic coordinates
What are the parallels of latitude for the north and south poles?

Back 7

90° north latitude and 90° south.

Front 8

401. The Earth and its geographic coordinates
What else do you call the 0° and 180° meridians of longitude?

Back 8

Greenwich meridian and international dateline, respectfully.

Front 9

401. The Earth and its geographic coordinates
What’s direction?

Back 9

The position of one point in space in relation to another without reference to the distance between them.

Front 10

401. The Earth and its geographic coordinates
What’s distance?

Back 10

The amount of space separating two points.

Front 11

402. Navigating environment
What happens to the movement of an object floating in the air?

Back 11

It moves downwind with the speed of the wind.

Front 12

402. Navigating environment
What two unrelated factors determine the path of an aircraft over the Earth?

Back 12

(1) The motion of the aircraft through an air mass.
(2) The motion of the air mass across the Earth’s surface.

Front 13

402. Navigating environment
What’s the intended path of an aircraft?

Back 13

The path the aircraft would travel over the Earth’s surface if there was no wind.

Front 14

402. Navigating environment
What’s the actual path of an aircraft?

Back 14

The path the aircraft travels over the Earth’s surface and includes the effects of wind.

Front 15

402. Navigating environment
What’s TR?

Back 15

The path of an aircraft over the Earth’s surface.

Front 16

402. Navigating environment
What’s TC?

Back 16

The intended path of an aircraft over the Earth’s surface.

Front 17

402. Navigating environment
What’s drift?

Back 17

The sideward displacement of an aircraft by the wind.

Front 18

402. Navigating environment
What’s GS?

Back 18

The rate of movement of an aircraft relative to the Earth’s surface.

Front 19

402. Navigating environment
What does a wind triangle represent?

Back 19

The effect of the wind on the flight of an aircraft.

Front 20

402. Navigating environment
What do you call the direction in which a magnetized needle is pointing when it’s only influenced
by the Earth’s magnetic field?

Back 20

Mag N.

Front 21

402. Navigating environment
What’s MAG VAR?

Back 21

The angle between true north and the direction indicated by the needle of a compass that’s influenced only
by the Earth’s magnetic field.

Front 22

402. Navigating environment
What do you call the lines on a navigation chart that connect points of equal MAG VAR?

Back 22

Isogonic lines.

Front 23

402. Navigating environment
What’s deviation?

Back 23

The deflection of a compass needle from Mag N.

Front 24

403. Aerial delivery fundamentals
List the five factors to consider to accurately drop a bomb.

Back 24

(1) Gravity.
(2) Airspeed.
(3) Air resistance.
(4) Wind speed.
(5) Wind direction.

Front 25

403. Aerial delivery fundamentals
When a bomber is flying too slowly, what effect does that have on a dropped bomb?

Back 25

The bomb will drop short.

Front 26

403. Aerial delivery fundamentals
What effect does air resistance have on a dropped bomb?

Back 26

A lag effect.

Front 27

403. Aerial delivery fundamentals
What effect does a strong tail wind have on a dropped bomb?

Back 27

It can cause the bomb to overshoot the target.

Front 28

403. Aerial delivery fundamentals
What two mission data tables affect the bombing parameters?

Back 28

(1) ST.
(2) AP table.

Front 29

403. Aerial delivery fundamentals
What are the requirements of the ST for a nuclear mission?

Back 29

A separate entry is required for each position on the launcher and each weapon type is identified.

Front 30

403. Aerial delivery fundamentals
What does the AP table represent?

Back 30

The preplanned flight route of the aircraft.

Front 31

404. Inertial navigation principles
List the five advantages of an INS.

Back 31

(1) Neither transmit nor receive any electromagnetic signals.
(2) Shows accurate velocity during maneuvering.
(3) Gives continuous attitude references.
(4) Gives instantaneous aircraft present position data.
(5) Is extremely accurate.

Front 32

404. Inertial navigation principles
On what basic principles do INSs operate?

Back 32

They measure aircraft acceleration, and establishing a frame of reference and sensing motion with it.

Front 33

404. Inertial navigation principles
What basic inertial navigation components are required to determine vehicle rate?

Back 33

An accelerometer, platform, integrator, and computer.

Front 34

404. Inertial navigation principles
What is an accelerometer?

Back 34

A measuring device that measures acceleration/deceleration.

Front 35

404. Inertial navigation principles
How are accelerometers protected to reduce all possible sources of errors?

Back 35

Against temperature and pressure changes.

Front 36

404. Inertial navigation principles
What’s the output signal of an accelerometer?

Back 36

Acceleration.

Front 37

404. Inertial navigation principles
What type of platform maintains accelerometer orientation?

Back 37

A gyro-stabilized platform.

Front 38

404. Inertial navigation principles
What’s the output of the first integrator in an INS?

Back 38

Velocity.

Front 39

404. Inertial navigation principles
What’s the output of the second integrator in an INS?

Back 39

Distance.

Front 40

404. Inertial navigation principles
What’s the primary function of the computer in an INS?

Back 40

To compute aircraft present position.

Front 41

405. ASQ–184 inertial navigation system
Describe the INS used on the B–1B aircraft.

Back 41

The ASQ–184 system consists of two INS channels, each consisting of one INU and two INU transformers.

Front 42

405. ASQ–184 inertial navigation system
What data is provided by the INS reference?

Back 42

Aircraft roll, pitch, and yaw.

Front 43

405. ASQ–184 inertial navigation system
How many gimbals are mounted on the gyro-stabilized platform?

Back 43

Four.

Front 44

405. ASQ–184 inertial navigation system
What senses all movement of the aircraft?

Back 44

The platform accelerometers.

Front 45

405. ASQ–184 inertial navigation system
What’s the function of the PE?

Back 45

To monitor the gyro-stabilized platform performance and relay information to the I/O assembly.

Front 46

405. ASQ–184 inertial navigation system
What aircraft systems receive data from the INS?

Back 46

RS, ACUC, flight instruments signal converter #1 and #2, flight instrument test & mode select, TACAN,
HSI, VSDI #1 and #2, FDC/MON #1 and #2, automatic flight control, MDIs, keyer control, NAV/AUX
control, and weapons.

Front 47

405. ASQ–184 inertial navigation system
What aircraft systems provide data to the INS?

Back 47

RS, Doppler radar, CADC #1 and #2, gyro stabilization, IKB, and NAV/AUX control.

Front 48

405. ASQ–184 inertial navigation system
What’re the functions of the NAV computer?

Back 48

It calculates position and velocity, synchronizes data flow, and monitors unit performance.

Front 49

405. ASQ–184 inertial navigation system
What does the CPU indicator for the front of the INU indicate?

Back 49

That the CPU has failed.

Front 50

405. ASQ–184 inertial navigation system
Which ACUC data bus allows the INS to communicate with all other aircraft systems?

Back 50

AMUX data bus A.

Front 51

406. Modes of operation
What are the INU modes of operation?

Back 51

Off, turn-on and initialization, stored heading align, air align, navigate, precision align, attitude, and test.

Front 52

406. Modes of operation
During turn-on and initialization of the INU, what’s the time period for the INU to complete a
successful INU initialization?

Back 52

Within 440 seconds.

Front 53

406. Modes of operation
What’s the stored heading align mode of the INU?

Back 53

A fast-reaction align mode in which alignment data is already available.

Front 54

406. Modes of operation
What information is the INU initialized with during an air align mode?

Back 54

Position, heading, ALT, and velocity.

Front 55

406. Modes of operation
Name the three methods used to update the navigate function of the INU.

Back 55

(1) Doppler-aided.
(2) TAS.
(3) Pure inertial.

Front 56

406. Modes of operation
What’s the approximate duration of the INU precision align mode?

Back 56

45 minutes.

Front 57

406. Modes of operation
What maintains platform level during the INU attitude mode?

Back 57

Hardware control.

Front 58

406. Modes of operation
Describe the INU BIT self-test?

Back 58

A 6-minute course alignment, followed by a 30°/hr slew on all three axes through predicted angles under
software control.

Front 59

407. Purpose of the global positioning system
How many satellites can be observed at any location on the earth by the GPS system?

Back 59

Four.

Front 60

407. Purpose of the global positioning system
What type of information is gathered by the monitor stations as they track the satellites?

Back 60

Position information and clock data from each satellite.

Front 61

407. Purpose of the global positioning system
Define ephemeris data.

Back 61

Information used to calculate exact position and clock error for each satellite (position information for
celestial bodies).

Front 62

407. Purpose of the global positioning system
How often is almanac data transmitted?

Back 62

Once every 24 hours.

Front 63

407. Purpose of the global positioning system
What are the frequencies of the two signals transmitted from the satellite?

Back 63

(1) L1 1575.45 MHz.
(2) L2 1227.6 MHz.

Front 64

407. Purpose of the global positioning system
The NAV set retrieves satellite data to compute what factors?

Back 64

Three-dimensional position, speed, and precise time information.

Front 65

407. Purpose of the global positioning system
What factors does the FOM take into account?

Back 65

Equipment status and performance, jamming-to-signal ratio, tracking loop performance, receiver operating
state and NAV mode, time correlation of the GPS and the aiding NAV system, and satellite performance
(including the number of satellites being used).

Front 66

408. Characteristics and components of the global positioning system
What’s the three-dimension NAV accuracy of position? Of time?

Back 66

16 meters; 100 nanoseconds.

Front 67

408. Characteristics and components of the global positioning system
What type of power is available for memory storage when primary power is not applied?

Back 67

Three C-cell alkaline batteries.

Front 68

408. Characteristics and components of the global positioning system
What’s the maximum GPS speed that can be displayed by the system?

Back 68

9,999 knots.

Front 69

408. Characteristics and components of the global positioning system
What makes the GPS NAV system ideal for the military?

Back 69

Antijamming, global capabilities, all-weather usage, extreme accuracy, and system passiveness (no
transmitter to be tracked).

Front 70

408. Characteristics and components of the global positioning system
Which of the ARN–151 units requires no power, adjustments, or controls to function?

Back 70

Antenna.

Front 71

408. Characteristics and components of the global positioning system
What’s the purpose of the antenna amplifier AM–7314?

Back 71

To amplify and downconvert RF satellite signals into separate L1 and L2 IF signals, and send the IF signals
to the receiver.

Front 72

408. Characteristics and components of the global positioning system
What’s the purpose of the antenna controller?

Back 72

To amplify the RF satellite signal, convert it to IF and send it to the receiver, and provide discrimination
against jamming signals.

Front 73

408. Characteristics and components of the global positioning system
How is GPS data displayed?

Back 73

On the indicator control.

Front 74

409. Operating principles of the global positioning system components
What NAV information is produced by the receiver?

Back 74

Position coordinates, ALT, time, and speed.

Front 75

409. Operating principles of the global positioning system components
What are the three basic operations of the receiver?

Back 75

(1) Initialization.
(2) Satellite tracking and NAV solution.
(3) Output.

Front 76

409. Operating principles of the global positioning system components
What information is input into the GPS receiver by the operator to initialize the system?

Back 76

Present position, time, and almanac information (if not available from memory).

Front 77

409. Operating principles of the global positioning system components
On initialization, what sources provide position, time, and almanac information to the receiver?

Back 77

The C–11702 indicator control, a data loader, up to two INS systems, PTTI equipment, a 1553 data bus
from the aircraft, or critical memory in the receiver.

Front 78

409. Operating principles of the global positioning system components
List the four receiver interfaces.

Back 78

(1) 1553.
(2) PTTI.
(3) Instrument.
(4) ARINC.

Front 79

409. Operating principles of the global positioning system components
What type of language does the PTTI interface use?

Back 79

BCD.

Front 80

409. Operating principles of the global positioning system components
What type of format does the ARINC interface use?

Back 80

Computer words using specific voltage levels for high and lows.

Front 81

409. Operating principles of the global positioning system components
What data bus is used to route control commands from the C–11702 indicator control to the
receiver?

Back 81

The ARINC 429 data bus.

Front 82

409. Operating principles of the global positioning system components
Which LRU eliminates electronic jamming? How?

Back 82

The antenna controller; it nulls out (decreases) the unwanted signal by vector addition of all input signals.

Front 83

410. Types of radar sets and transmission principles
Which part of an RS sends out the RF signal?

Back 83

Transmitter.

Front 84

410. Types of radar sets and transmission principles
What’s another name for the reflected radar wave?

Back 84

Echo

Front 85

410. Types of radar sets and transmission principles
Upon what does the successfulness of an RS primarily depend?

Back 85

Its ability to measure distance in terms of time.

Front 86

410. Types of radar sets and transmission principles
How fast does an RF wave travel a nautical mile How about a radar mile?

Back 86

6.2μs; 12.4μs.

Front 87

410. Types of radar sets and transmission principles
If the echo from a target returns in 930μs, how far away is the target?

Back 87

75 miles.

Front 88

410. Types of radar sets and transmission principles
What are two basic problems that must be overcome in all RSs?

Back 88

(1) Having a powerful transmitter and receiver operating on the same frequency.
(2) Using a constant-frequency signal.

Front 89

410. Types of radar sets and transmission principles
Name the three radar systems that overcome the basic problems affecting RSs.

Back 89

(1) FM systems.
(2) Pulse-modulation systems.
(3) Frequency-shift systems.

Front 90

410. Types of radar sets and transmission principles
In an FM system, how many signals are fed to the receiver at one time?

Back 90

Two.

Front 91

410. Types of radar sets and transmission principles
Describe the operation of the transmitter in a pulse-modulation system.

Back 91

The transmitter is turned on for short periods of time and off for long periods of time.

Front 92

410. Types of radar sets and transmission principles
Upon what principle is the frequency-shift system based?

Back 92

Doppler.

Front 93

411. Components and characteristics of the pulse-modulation system
How is the length of the electromagnetic pulses in a pulse-modulation system measured?

Back 93

In microseconds.

Front 94

411. Components and characteristics of the pulse-modulation system
How does a longer pulse in a pulse-modulation system affect power and range?

Back 94

Longer pulses have more power, which makes it possible to cover a larger range of space.

Front 95

411. Components and characteristics of the pulse-modulation system
List the six basic RS components.

Back 95

(1) Power supply.
(2) Synchronizer.
(3) Transmitter.
(4) Antenna.
(5) Receiver.
(6) Indicator.

Front 96

411. Components and characteristics of the pulse-modulation system
What’s another name for the master timer in a basic RS?

Back 96

Synchronizer.

Front 97

411. Components and characteristics of the pulse-modulation system
Which component of a basic RS triggers the transmitter?

Back 97

Synchronizer.

Front 98

411. Components and characteristics of the pulse-modulation system
Which component of a basic RS produces short, powerful bursts of RF energy?

Back 98

Transmitter.

Front 99

411. Components and characteristics of the pulse-modulation system
What do you call the device that connects the antenna to the transmitter and receiver?

Back 99

Duplexer, circulator, or waveguide switch.

Front 100

411. Components and characteristics of the pulse-modulation system
Which component of a basic RS produces an IF signal?

Back 100

Receiver.

Front 101

411. Components and characteristics of the pulse-modulation system
Name four things that can be determined by the shape of the radar pulse.

Back 101

(1) Range accuracy.
(2) Minimum range.
(3) Maximum range.
(4) Target resolution.

Front 102

411. Components and characteristics of the pulse-modulation system
Range accuracy primarily depends on which part of the radar pulse?

Back 102

The leading edge.

Front 103

411. Components and characteristics of the pulse-modulation system
What property is provided by a flat-topped radar pulse of sufficiently long duration?

Back 103

Maximum range.

Front 104

411. Components and characteristics of the pulse-modulation system
What property does PD determine?

Back 104

Maximum range.

Front 105

411. Components and characteristics of the pulse-modulation system
What’s the relationship between PRT and PRF?

Back 105

PRT = 1/PRF.

Front 106

411. Components and characteristics of the pulse-modulation system
What’s the peak power of an RS?

Back 106

The maximum power of the radar pulse of an RT.

Front 107

411. Components and characteristics of the pulse-modulation system
What’s the average power of an RS?

Back 107

The power of an RT averaged over the whole PRT.

Front 108

412. Characteristics of the frequency-shift system
What principle makes it possible to instantaneously sense and measure GS and drift angle?

Back 108

Doppler.

Front 109

412. Characteristics of the frequency-shift system
Describe the Doppler principle involved when you listen to the whistle of a moving train.

Back 109

The frequency seems to increase as the train approaches and decrease as the train moves away.

Front 110

412. Characteristics of the frequency-shift system
What’s the frequency shift when the transmitter/receiver is at a constant distance from an object?

Back 110

Zero.

Front 111

412. Characteristics of the frequency-shift system
How does the frequency shift change when an object is closing in on the transmitter/receiver?

Back 111

Increases.

Front 112

412. Characteristics of the frequency-shift system
How does the frequency shift change when an object is moving away from the
transmitter/receiver?

Back 112

Decreases.

Front 113

413. Waveguide devices and their functions
What’s a waveguide?

Back 113

A transmission line comprising a hollow conducting tube within which electromagnetic waves may be
propagated.

Front 114

413. Waveguide devices and their functions
Name two types of waveguide.

Back 114

(1) Circular.
(2) Rectangular.

Front 115

413. Waveguide devices and their functions
What are two advantages of waveguides over other types of transmission lines?

Back 115

(1) Less power loss.
(2) Greater power- handling capabilities.

Front 116

413. Waveguide devices and their functions
Name the three types of power losses peculiar to RF transmission lines.

Back 116

(1) Copper.
(2) Dielectric.
(3) Radiation.

Front 117

413. Waveguide devices and their functions
Why are waveguides impractical at frequencies below 3,000 MHz?

Back 117

Because the physical size of the waveguide would be too large for practical use.

Front 118

413. Waveguide devices and their functions
What’s the function of the choke joint?

Back 118

To provide a good mechanical and electrical connection between waveguide sections.

Front 119

413. Waveguide devices and their functions
What’s the function of the dummy load?

Back 119

To terminate the RF energy in a resistive load, changing the RF energy into heat energy.

Front 120

413. Waveguide devices and their functions
What’s the purpose of the directional coupler?

Back 120

To provide a means of coupling energy between the waveguide and test equipment.

Front 121

413. Waveguide devices and their functions
Match each waveguide function in column A with the appropriate device in column B. Items in
column B may be used only once.
Column A
____ (1) Absorbs the transmitter power during testing.
____ (2) Allows measurement of RF energy in both directions.
____ (3) Transfers energy between the waveguide and free space.
____ (4) Allows measurement of RF energy in one direction.
____ (5) Protects the receiver circuits from the transmitter pulse.
Column B
a. Feedhorn.
b. Duplexer.
c. Dummy load.
d. Bidirectional coupler.
e. Directional coupler.

Back 121

(1) c.
(2) d.
(3) a.
(4) e.
(5) b.

Front 122

413. Waveguide devices and their functions
What factors do you compare to determine the VSWR of a waveguide?

Back 122

The reflected power to the transmitted power.

Front 123

413. Waveguide devices and their functions
How does a damaged waveguide affect the operation of an electronic system?

Back 123

Causes a mismatch that increases the VSWR, which reduces the power transferred through the waveguide.

Front 124

413. Waveguide devices and their functions
What should you look for during maintenance on the waveguide systems?

Back 124

Dirt, metal objects, other particles, and moisture.

Front 125

414. Representative antennas
Which system LRU contains servoamplifiers that furnish pitch and roll drive signals to the
antenna stabilization motors?

Back 125

Electronic control amplifier.

Front 126

414. Representative antennas
Which LRU provides stabilized pitch and roll reference data for control of antenna orientation?

Back 126

Stabilization data generator.

Front 127

414. Representative antennas
Which LRU uses PCMs to steer the RF beam?

Back 127

LOA.

Front 128

414. Representative antennas
What’s the function of the PCMs?

Back 128

To act as phase shifters and radiating elements.

Front 129

415. Characteristics and components of the AN/APN–224 radar altimeter
Describe the RA subsystem.

Back 129

A dual-channel, high-resolution, pulsed radar that computes aircraft ALT AGL from 0 to 5,000 feet.

Front 130

415. Characteristics and components of the AN/APN–224 radar altimeter
What components makeup each RA channel?

Back 130

An R/T, and dedicated transmit and receive antennas.

Front 131

415. Characteristics and components of the AN/APN–224 radar altimeter
What’s the operation of the RA based on?

Back 131

The exact measurement of the time required for a RF pulse to travel from the transmit antenna to the
terrain, and then back to the receive antenna.

Front 132

415. Characteristics and components of the AN/APN–224 radar altimeter
In what two modes does the RA operate?

Back 132

(1) Track.
(2) Search/loss of track.

Front 133

416. Types of radar applications
What’s a radar ground map?

Back 133

Pictorial map of the terrain.

Front 134

416. Types of radar applications
What does weather radar provide?

Back 134

A visual indication of storm conditions at ranges up to 300 NMs.

Front 135

416. Types of radar applications
How is target range determined?

Back 135

By measuring the time the radio waves take to reach the target and return.

Front 136

416. Types of radar applications
What’s the primary function of TF radar?

Back 136

To provide the signals necessary for automatic TF flight.

Front 137

416. Types of radar applications
What’s TA radar used for?

Back 137

To display all forward terrain at and above the aircraft’s ALT.

Front 138

417. Principles of amplitude-modulated transmitters
Which AM transmitter component generates a low-amplitude signal at a low frequency?

Back 138

Master oscillator.

Front 139

417. Principles of amplitude-modulated transmitters
What is used to produce the “load’ on the oscillator in an AM transmitter?

Back 139

Low-frequency, low-power signal applied to a system of multipliers and power amplifiers.

Front 140

417. Principles of amplitude-modulated transmitters
Which AM transmitter section controls the overall stability of the system?

Back 140

Oscillator.

Front 141

417. Principles of amplitude-modulated transmitters
What’s the function of the buffer in an AM transmitter?

Back 141

To isolate the oscillator from the multiplier and amplifier load.

Front 142

417. Principles of amplitude-modulated transmitters
What’s used to increase the AM oscillator frequency to the designed frequency required for
carrier wave operation?

Back 142

Combinations of doublers and triplers.

Front 143

417. Principles of amplitude-modulated transmitters
What’s the function of the power amplifiers in an AM transmitter?

Back 143

To bring the level of the carrier up to the appropriate power level for transmission.

Front 144

417. Principles of amplitude-modulated transmitters
Why is an intermediate power amplifier sometimes required in an AM transmitter?

Back 144

To establish a more appropriate level of ‘driving’ power at the input to the final amplifier.

Front 145

417. Principles of amplitude-modulated transmitters
Which AM transmitter component modulates the audio signal from the modulator with the carrier
wave from the RF unit?

Back 145

Final amplifier.

Front 146

417. Principles of amplitude-modulated transmitters
What’s the name of the process used in modulating AM signals?

Back 146

Heterodyning

Front 147

417. Principles of amplitude-modulated transmitters
What’s the purpose of the audio power amplifier in the modulator section of an AM transmitter?

Back 147

To receive its driving signal from the audio voltage amplifier and amplify the signal to the proper level for
modulating the carrier wave at the final power amplifier in the RF section.

Front 148

417. Principles of amplitude-modulated transmitters
To achieve AM modulation, how must the modulation amplifier be operated?

Back 148

In a nonlinear manner.

Front 149

417. Principles of amplitude-modulated transmitters
What are the two prominent frequencies created by the heterodyning process?

Back 149

(1) The sum of the two original frequencies.
(2) The difference between the two original frequencies.

Front 150

418. Principles of frequency modulation
What’s another name for the unmodulated carrier in an FM system?

Back 150

The rest or center frequency.

Front 151

418. Principles of frequency modulation
What controls the amount of frequency deviation in an FM signal?

Back 151

The amplitude of the modulating signal.

Front 152

418. Principles of frequency modulation
What aspect of the FM signal is controlled by the amplitude of the modulating signal?

Back 152

The amount of frequency deviation.

Front 153

418. Principles of frequency modulation
What determines the amount of separation between the sideband frequencies of an FM wave?

Back 153

The frequency of the audio modulating signal.

Front 154

418. Principles of frequency modulation
At what power level are sidebands in an FM signal considered significant?

Back 154

At least 1 percent of the unmodulated carrier power.

Front 155

418. Principles of frequency modulation
What does the MI (deviation ratio) in an FM system identify?

Back 155

The number of significant sidebands available in a given FM signal.

Front 156

418. Principles of frequency modulation
What controls the bandwidth when you’re using a given modulating signal frequency?

Back 156

Amplitude of the modulating signal.

Front 157

418. Principles of frequency modulation
What happens to carrier power, sideband power, and total power when the percentage of
modulation in an FM signal increases?

Back 157

Sideband power increases, carrier power decreases, and total power remains constant.

Front 158

419. Principles of frequency-modulated transmitters
What’s the overall purpose of the FM transmitter AFC circuit?

Back 158

To stabilize the output center frequency.

Front 159

419. Principles of frequency-modulated transmitters
What controls the reactance that controls the oscillator frequency in an FM reactance modulator?

Back 159

The audio signal from the audio amplifier.

Front 160

419. Principles of frequency-modulated transmitters
What’s the purpose of the frequency multiplier in an FM transmitter?

Back 160

To raise the modulated frequencies to the assigned channel and increase the amount of frequency deviation
to the maximum allowable.

Front 161

419. Principles of frequency-modulated transmitters
What’s the function of the discriminator in the AFC circuit?

Back 161

To detect any change in the converter’s difference frequency and produce an AFC correction voltage to
vary the reactance of the modulator, causing the oscillator to return to the desired center frequency.

Front 162

419. Principles of frequency-modulated transmitters
What’s the purpose of the preemphasis circuit in the audio amplifier?

Back 162

To overcome the difference between the high- and low-frequency components in the transmitted signal.

Front 163

420. Principles of single-sideband transmitters
Why are SSB transmitters considered to be frequency spectrum conservers?

Back 163

In SSB, the carrier isn’t transmitted and only one sideband is transmitted.

Front 164

420. Principles of single-sideband transmitters
Why is frequency stability so important in SSB?

Back 164

Since the carrier isn’t transmitted in SSB, it must be inserted in the receiver for demodulation.

Front 165

420. Principles of single-sideband transmitters
Which term describes when an SSB transmitter is transmitting both sidebands, but no carrier?

Back 165

ISB.

Front 166

420. Principles of single-sideband transmitters
Which term describes when an SSB transmitter is transmitting only one sideband and the carrier?

Back 166

AME

Front 167

420. Principles of single-sideband transmitters
What’s the purpose of the sideband filter circuit?

Back 167

To eliminate one sideband, leaving only the desired sideband to be amplified.

Front 168

420. Principles of single-sideband transmitters
Why is a linear RF power amplifier required in SSB?

Back 168

To increase the power without introducing distortion.

Front 169

420. Principles of single-sideband transmitters
What components are used in the SSB transmitter to raise the SSB frequency to the desired
radiation frequency?

Back 169

A balanced mixer and HF oscillator.

Front 170

420. Principles of single-sideband transmitters
What led to the development of the frequency synthesizer?

Back 170

The need to select one of hundreds of channels at the flip of a switch, reduce ground bands, and utilize
channels in the UHF range.

Front 171

421. Receiver functions and characteristics
Explain the following terms:
a. Selection.
b. Sensitivity.
c. Noise.
d. Selectivity.

Back 171

a. The ability of the receiver to select a particular frequency of a station from all other station frequencies
appearing at the antenna of the receiver.
b. The ability of a receiver to reproduce weak signals.
c. A major limiting factor of sensitivity because it can prevent the receiver from responding to very low
signal inputs.
d. Ability of a receiver to distinguish between the desired signal and unwanted signals nearby in operating
frequency.

Front 172

421. Receiver functions and characteristics
Why is it almost impossible to have a high degree of selectivity and fidelity simultaneously?

Back 172

To have good fidelity, a receiver must have a wide bandwidth; good selectivity requires a receiver to have a
narrow frequency band.

Front 173

423. Operating characteristics of a frequency-modulated receiver
Why must an FM receiver have a wideband IF amplifier stage?

Back 173

To receive and pass all the side-frequency components of the modulated signal without distortion.

Front 174

423. Operating characteristics of a frequency-modulated receiver
What two fundamental sections of the FM receiver are electrically different from an AM
receiver?

Back 174

(1) Discriminator (detector).
(2) Limiter.

Front 175

423. Operating characteristics of a frequency-modulated receiver
What’s the difference between AM and FM demodulation?

Back 175

AM demodulation involves the detection of variations in the amplitude of the signal; FM demodulation is
the process of detecting variations in the frequency of the signal.

Front 176

423. Operating characteristics of a frequency-modulated receiver
What function does the limiter circuit perform?

Back 176

Removes amplitude variations from the signal to minimize noise interference.

Front 177

423. Operating characteristics of a frequency-modulated receiver
What’s the function of a discriminator circuit?

Back 177

To extract the audio frequency component from the FM signal.

Front 178

423. Operating characteristics of a frequency-modulated receiver
Why does FM provide more realistic sound reproduction?

Back 178

Because of an increase in the number of sidebands.

Front 179

423. Operating characteristics of a frequency-modulated receiver
Describe the benefits of receivers using double or triple frequency conversion.

Back 179

Very selective and suppress image signals to yield sharp signal discrimination.

Front 180

422. Operating characteristics of an amplitude-modulated receiver
What two signals are heterodyned in the receiver mixer to produce the IF signal?

Back 180

(1) Incoming RF signal.
(2) Local oscillator signal.

Front 181

422. Operating characteristics of an amplitude-modulated receiver
Explain the term ganged tuning.

Back 181

The process used to tune two or more circuits with a single control.

Front 182

422. Operating characteristics of an amplitude-modulated receiver
How many stages of IF amplification may a superheterodyne receiver contain?

Back 182

As many as needed to obtain the desired power output.

Front 183

422. Operating characteristics of an amplitude-modulated receiver
What is heterodyning? What does it produce?

Back 183

The process of mixing the input RF signal with the local oscillator signal; four different frequencies—two
original frequencies, their sum, and their difference.

Front 184

422. Operating characteristics of an amplitude-modulated receiver
What’s the purpose of the detector circuit?

Back 184

To extract the modulating audio signal.

Front 185

424. Operating characteristics of a single-sideband receiver
What are the two reasons SSB communications are better than AM?

Back 185

(1) Narrower receiver bandpass.
(2) The ability to place more signals in a small portion of the frequency spectrum.

Front 186

424. Operating characteristics of a single-sideband receiver
List three disadvantages of SSB.

Back 186

(1) Frequency stability is very critical.
(2) A weak SSB signal is sometimes completely hidden from the receiver by a stronger signal.
(3) A carrier of proper frequency and amplitude must be reinserted at the receiver.

Front 187

424. Operating characteristics of a single-sideband receiver
What’s the difference between the SSB receiver and AM receiver?

Back 187

A special type of detector and a carrier reinsertion oscillator must be used in an SSB receiver.

Front 188

424. Operating characteristics of a single-sideband receiver
Why must a carrier be reinserted in an SSB receiver?

Back 188

To receive the SSB signal and produce the original signal.

Front 189

424. Operating characteristics of a single-sideband receiver
Let’s say a SSB receiver is receiving voice communications and the SSB carrier reinsertion
oscillator starts drifting off frequency. What would be the result of this action?

Back 189

Speech could be unintelligible because the oscillator drifted off the original frequency.

Front 190

425. Antennas
What’s the function of an antenna?

Back 190

To radiate electromagnetic energy into or collect electromagnetic energy from space.

Front 191

425. Antennas
Why is an antenna considered to be a transducer?

Back 191

Because it converts energy in the form of current oscillations to electric and magnetic fields of force.

Front 192

425. Antennas
How does an antenna convert received fields back into RF current?

Back 192

When the electromagnetic fields traveling through space cut across the receive antenna, they impress a
voltage across the antenna, which causes a current to flow to a receiver.

Front 193

425. Antennas
What’s required of the transmitting/receiving antennas to provide maximum communicating
distance?

Back 193

Maximum efficiency.

Front 194

426. Radio-frequency transmission lines
Name the three types of RF transmission lines.

Back 194

(1) Parallel two-wire.
(2) Shielded pair.
(3) Coaxial.

Front 195

426. Radio-frequency transmission lines
What are the principal disadvantages of two-wire open lines?

Back 195

The high-radiation losses and noise pickup due to the lack of shielding.

Front 196

426. Radio-frequency transmission lines
Which transmission line has uniform capacitance between the conductors throughout the length
of the line?

Back 196

Shielded pair.

Front 197

426. Radio-frequency transmission lines
What’s the chief advantage of coaxial cable over parallel two-wire line?

Back 197

It minimizes radiation losses and noise pickup from other lines.

Front 198

426. Radio-frequency transmission lines
What is the relationship between the SWR and the line and load impedances?

Back 198

The higher the SWR, the greater the mismatch between the line impedance and load impedance.

Front 199

426. Radio-frequency transmission lines
Name the three types of losses in transmission lines.

Back 199

(1) Copper.
(2) Dielectric.
(3) Radiation/induction.

Front 200

427. Characteristics of high-frequency systems
What’s the purpose of HF radios?

Back 200

To provide long-range communication.

Front 201

427. Characteristics of high-frequency systems
Name the four primary disadvantages associated with HF transceivers.

Back 201

(1) Higher transmitter power.
(2) Narrower bandwidth.
(3) Carrier wave power.
(4) Lower fidelity.

Front 202

427. Characteristics of high-frequency systems
What’s the primary reason for using SSB modulation?

Back 202

Because of the need for many channels in HF radio.

Front 203

427. Characteristics of high-frequency systems
How many channels does a typical HF radio have? What’s the spacing between each channel?

Back 203

280,000; 100 Hz.

Front 204

427. Characteristics of high-frequency systems
When using the USB mode, what’s the transmitted frequency when the HF control box is set to
25.000 MHz and the signal is modulated by a 1000-Hz tone?

Back 204

25.001 MHz.

Front 205

427. Characteristics of high-frequency systems
What’s the difference between normal AM and AME signals?

Back 205

AM consists of the carrier and both sidebands ; AME consists of the carrier and only one sideband.

Front 206

427. Characteristics of high-frequency systems
Why is an antenna coupler required in an HF system?

Back 206

To match the impedance of the antenna to the selected frequency.

Front 207

428. Capabilities and major components of the ARC–190 high-frequency radio system
What’s the frequency range of the ARC–190 system?

Back 207

3.0000 to 29.9999 MHz.

Front 208

428. Capabilities and major components of the ARC–190 high-frequency radio system
Name the six modes of transmission and reception.

Back 208

(1) USB voice.
(2) LSB voice.
(3) USB data.
(4) LSB data.
(5) AME.
(6) CW.

Front 209

428. Capabilities and major components of the ARC–190 high-frequency radio system
What are the major components of the ARC–190 system?

Back 209

R/T, control box, and antenna coupler.

Front 210

428. Capabilities and major components of the ARC–190 high-frequency radio system
How does the ARC–190 receiver minimize the effects of strong interfering signals?

Back 210

By using dual conversion and crystal band-pass filters.

Front 211

428. Capabilities and major components of the ARC–190 high-frequency radio system
What’s the ARC–190 tune time when using a learned preset?

Back 211

Less than 35 milliseconds.

Front 212

428. Capabilities and major components of the ARC–190 high-frequency radio system
What’s the major functional difference between the three versions of the RT–1341?

Back 212

The RT–1341(V)1 works only with coupler CU–2275(V)1; the other R/Ts work with all couplers.

Front 213

428. Capabilities and major components of the ARC–190 high-frequency radio system
What form of frequency control data is sent between the R/T and control box?

Back 213

Serial ASCII control words at a rate of 9600 bauds.

Front 214

428. Capabilities and major components of the ARC–190 high-frequency radio system
Why is the tuner section of the antenna coupler pressurized?

Back 214

To prevent high-voltage arcing at high altitudes, provide a uniform cooling medium, and prevent corrosive
elements from getting in.

Front 215

428. Capabilities and major components of the ARC–190 high-frequency radio system
Why does the antenna coupler need to match the impedance of the antenna to the R/T unit?

Back 215

For maximum power transfer.

Front 216

428. Capabilities and major components of the ARC–190 high-frequency radio system
When does the R/T’s external blower come on?

Back 216

When the R/T is keyed and for about a minute after it’s unkeyed.

Front 217

429. Purposes and characteristics of very-high frequency systems
What propagation characteristic do the VHF systems share?

Back 217

They’re operated by LOS.

Front 218

429. Purposes and characteristics of very-high frequency systems
Which comm/nav systems operate in the VHF spectrum?

Back 218

VHF AM and FM, VOR localizer, and ILS.

Front 219

429. Purposes and characteristics of very-high frequency systems
What’s the main use for military FM radio?

Back 219

Communicating with Army and other ground units.

Front 220

429. Purposes and characteristics of very-high frequency systems
Why do you need a VHF AM radio on an aircraft?

Back 220

Alternate command radio and alternate link to control towers, especially those of civilian and foreign
agencies.

Front 221

429. Purposes and characteristics of very-high frequency systems
Which VHF radio communications extends beyond the LOS?

Back 221

FM.

Front 222

429. Purposes and characteristics of very-high frequency systems
Which VHF systems need antenna tuning?

Back 222

FM.

Front 223

429. Purposes and characteristics of very-high frequency systems
How many antennas does a VHF AM/FM radio need for communications and DF?

Back 223

Five.

Front 224

430. Capabilities and configurations of the ARC–186 very-high frequency radio
How far apart are the channels of the ARC–186 system?

Back 224

1. 25 kHz.

Front 225

430. Capabilities and configurations of the ARC–186 very-high frequency radio
To which frequencies of the VHF spectrum can the ARC–186 tune?

Back 225

FM is 30 – 87.975 MHz; AM is 108 – 151.975 MHz.

Front 226

430. Capabilities and configurations of the ARC–186 very-high frequency radio
On which of these frequencies can the ARC–186 only receive?

Back 226

108 – 115.975 MHz.

Front 227

430. Capabilities and configurations of the ARC–186 very-high frequency radio
Which LRU is only required in an installation where there is no available source for +28-VDC
power?

Back 227

PP–7541 power supply.

Front 228

430. Capabilities and configurations of the ARC–186 very-high frequency radio
Why is the C–11029 considered a true comm/nav control box?

Back 228

Because it controls the ARC–186 R/T and the VOR/ILS receiver.

Front 229

431. Purpose of ultra-high frequency equipment
What type of communications are UHF radios used for?

Back 229

Short range air-to-ground and air-to-air.

Front 230

431. Purpose of ultra-high frequency equipment
When the ARC–164 was originally introduced, what was its main advantage?

Back 230

High reliability.

Front 231

431. Purpose of ultra-high frequency equipment
How many frequencies can the ARC–164 transmitter operate on?

Back 231

7,000.

Front 232

431. Purpose of ultra-high frequency equipment
How does the HQ program resist jamming?

Back 232

By frequency hopping.

Front 233

431. Purpose of ultra-high frequency equipment
Why is it difficult for enemies to jam HQ transmissions?

Back 233

Because they never know what frequency the radios are operating on.

Front 234

431. Purpose of ultra-high frequency equipment
Why does frequency hopping work with multiple HQ radios?

Back 234

Because all HQ radios frequency hop to the same frequencies at the same time.

Front 235

431. Purpose of ultra-high frequency equipment
How could an enemy effectively jam HQ communications?

Back 235

By jamming the entire UHF band.

Front 236

432. Characteristics of HAVE QUICK II
What three entries are required to operate in the AJ mode?

Back 236

(1) WOD.
(2) TOD.
(3) Net number.

Front 237

432. Characteristics of HAVE QUICK II
What prevents WODs from being lost when power is removed from the radio set?

Back 237

They’re stored in non-volatile memory in the R/T.

Front 238

432. Characteristics of HAVE QUICK II
How many WODs can be loaded into memory?

Back 238

Six.

Front 239

432. Characteristics of HAVE QUICK II
How does the HQII radio know which WOD to use?

Back 239

A date code is loaded in memory location 14 for each word.

Front 240

432. Characteristics of HAVE QUICK II
What entry ensures HQII radios frequency hop at the same instant in time?

Back 240

TOD.

Front 241

432. Characteristics of HAVE QUICK II
What entry establishes an HQII radio’s entry point to the frequency-hopping pattern?

Back 241

Net number.

Front 242

432. Characteristics of HAVE QUICK II
What’s conferencing?

Back 242

The ability of an HQII radio to receive two signals simultaneously.

Front 243

432. Characteristics of HAVE QUICK II
What type of bandpass characteristics makes conferencing possible?

Back 243

Wideband.

Front 244

432. Characteristics of HAVE QUICK II
In what two configurations is the ARC–164 available?

Back 244

(1) Remote controlled.
(2) Panel mount.

Front 245

432. Characteristics of HAVE QUICK II
What configuration was most often used as a replacement for an older radio?

Back 245

Remote controlled.

Front 246

432. Characteristics of HAVE QUICK II
What’s the function of the data converter found on remote R/T units?

Back 246

To interface between the control unit and R/T.

Front 247

432. Characteristics of HAVE QUICK II
What’s an ID–1961?

Back 247

Remote frequency/channel indicator.

Front 248

432. Characteristics of HAVE QUICK II
With the MWOD modification, how many WODs can be loaded?

Back 248

Six.

Front 249

432. Characteristics of HAVE QUICK II
What’s the purpose of the modification providing the capability to use ANVIS green panel
lighting?

Back 249

To allow the use of the radio set with night vision goggle equipment.

Front 250

433. Multimode communications
What does the AN/ARC 210 R/T provide?

Back 250

Half-duplex, two-way communications of normal and secure voice AM or FM signals.

Front 251

433. Multimode communications
How do the upper and lower ARC 210 R/T antennas complement each other?

Back 251

By providing spherical antenna coverage.

Front 252

433. Multimode communications
What does the V/UHF2 radio set control provide?

Back 252

Controls and indicators for operation and frequency selection of the R/T.

Front 253

433. Multimode communications
What operations are controlled by the V/UHF2 radio set control?

Back 253

Normal, HQ, HQII, SINCGARS, and SATCOM.