Fcc Radar Element 8

Front 1

Which of the following has NO effect on the maximum range capability?

Back 1

Recovery Time

Front 2

What RADAR component controls timing throughout the system?

Back 2

Synchronizer

Front 3

The sweep frequency of a RADAR indicator is determined by what parameter?

Back 3

Pulse repetition frequency

Front 4

A radio wave will travel a distance of three nautical miles in?

Back 4

18.51 microseconds

Front 5

One RADAR mile is how many microseconds?

Back 5

12.34

(Remember - 1234)

Front 6

Radar range is measured by the constant:

Back 6

150 meters per microsecond

Front 7

What is the distance in nautical miles to a target if it takes 308.5 microseconds for the radar pulse to travel from the RADAR antenna to the target and back.

Back 7

25 nautical miles

Front 8

Frequencies generally used for marine RADAR are in the ____ part of the spectrum.

Back 8

SHF

(Super High Frequency)

Front 9

An S-band RADAR operates in which frequency band?

Back 9

2 - 4 GHz

Front 10

The major advantage of an S-band RADAR over an X-band RADAR is:

Back 10

It is less affected by weather conditions.

Front 11

A shipboard RADAR transmitter has a pulse repetition frequency (PRF) of 1,000 Hz, a pulse width of 0.5 microseconds, peak power of 150 KW, and a minimum range of 75 meters. Its duty cycle is:

Back 11

D. 0.0005

Front 12

If a RADAR transmitter has a pulse repetition frequency (PRF) of 900 Hz, a pulse width of 0.5 microseconds and a peak power of 15 kilowatts, what is its average power output?

Back 12

C. 6.75 watts.

Front 13

A search RADAR has a pulse width of 1.0 microsecond, a pulse repetition frequency (PRF) of 900 Hz, and an average power of 18 watts. The unit's peak power is:

Back 13

C. 20 Kilowatts

Front 14

For a range of 100 nautical miles, the RADAR pulse repetition frequency should be:

Back 14

B. 810 Hz or less

Front 15

Short range RADARs would most likely transmit:

Back 15

A. Narrow pulses at a fast rate.

Front 16

For a range of 10 nautical miles, the RADAR pulse repetition frequency (PRF) should be:

Back 16

A. Approximately 8.1 kHz or less.

Front 17

If the PRF is 2500 Hz, what is the PRI?

Back 17

B. 400 Microseconds

Divide time by frequency. They are inverse.

Front 18

If the pulse repetition frequency (PRF) is 2000 Hz, what is the pulse repetition interval (PRI)?

Back 18

C. 0.0005 seconds.

Divide time by frequency. They are inverse.

1/2000 = .0005

Front 19

If the RADAR unit has a pulse repetition frequency (PRF) of 2000 Hz and a pulse width of 0.05 microseconds, what is the duty cycle?

Back 19

A. 0.0001

Duty Cycle = Pulse Width / Pulse Rep Interval

Front 20

What is the relationship between pulse repetition rate and pulse width?

Back 20

D. Lower PRR with wider pulse width.

Front 21

A basic sample-and-hold circuit contains:

Back 21

D. An analog switch, a capacitor, amplifiers and input and output buffers.

Front 22

When comparing a TTL and a CMOS NAND gate:

Back 22

A. Both have active pull-up characteristics.

Front 23

Silicon crystals:

Back 23

D. All of these.

Sensitive, Wrapped in lead foil, tolerate low current.

Front 24

The basic frequency determining element in a Gunn oscillator is:

Back 24

C. The resonate cavity.

Front 25

The primary operating frequency of a reflex klystron is controlled by the:

Back 25

A. Dimensions of the resonant cavity.

Front 26

A Gunn diode oscillator takes advantage of what effect?

Back 26

D. Negative resistance and bulk-effect.

Front 27

The phantastron circuit is capable of:

Back 27

D. Developing a linear ramp voltage when triggered by an external source.

Front 28

The block diagram of a typical RADAR system microprocessor is shown in Fig 8A2. Choose the most correct statement regarding this system.

Back 28

A. The ALU executes arithmetic manipulations.

(Arithmetic Logic Unit)

Front 29

Choose the most correct statement:

Back 29

C. The filament of the magnetron carries dangerous voltages.

Front 30

If more light strikes the photodiode in Fig 8A5, there will be:

Back 30

C. More diode current.

(Resistance goes down)

Front 31

In the circuit shown in fig 8A6, which of the following is true?

Back 31

B. With either A or B low, Q1 is saturated and Q2 is off.

Front 32

You are troubleshooting a component on a printed circuit board in a RADAR system while referencing the Truth Table in Fig 8A8. What kind of integrated circuit is the component?

Back 32

A. D-type Flip-Flop, 3-State, Inverting

Front 33

The purpose of the modulator is to:

Back 33

B. Provide high voltage pulses of the proper shape and width to the magnetron.

Front 34

Which of the following statements about most modern RADAR transmitter power supplies is false?

Back 34

A. High voltage supplies may produce voltages in excess of 5,000 volts AC.

Front 35

The purpose of the Pulse Forming Network is to:

Back 35

C. Produce a pulse of the correct width.

Front 36

Which of the following is not part of the transmitting system?

Back 36

D. Klystron.

Front 37

High voltage is applied to what element of the magnetron?

Back 37

D. the cathode.

Front 38

The characteristic of the magnetron output pulse that relates to accurate range measurement is its:

Back 38

C. Rise time.

Front 39

What device is used as a transmitter in a marine RADAR system?

Back 39

A. Magnetron

Front 40

In a solid-state RADAR modulator, the duration of the transmitted pulse is determined by:

Back 40

C. The pulse forming network.

Front 41

The modulation frequency of most RADAR systems is between:

Back 41

A. 60 and 500 Hz

Front 42

In a pulse modulated magnetron what device determines the shape and width of the pulse?

Back 42

A. Pulse Forming Network

Front 43

The purpose of a modulator in the transmitter section of a RADAR is to:

Back 43

B. Provide the correct wave form to the transmitter.

Front 44

The purpose of the pulse-forming network is to:

Back 44

A. Determine the width of the modulating pulses.

Front 45

Pulse-forming networks are usually composed of the following:

Back 45

B. Series inductors and shunt capacitors.

Front 46

An artificial transmission line is used for:

Back 46

C. Determining the shape and duration of pulses.

Front 47

A ferrite circulator is most commonly used in what portion of the RADAR system?

Back 47

C. The duplexer

Front 48

A directional coupler has an attenuation of -30 db. A measurement of 100 milliwwatts at the coupler indicates the power of the line is:

Back 48

B. 100 Watts

Front 49

What is the purpose or function of the RADAR duplexer/circulating?

Back 49

A. An electronic switch that allows the use of one antenna for both transmission and reception.

Front 50

The ATR box:

Back 50

B. Prevents the received signal from entering the transmitter.

Front 51

When a pulse RADAR is radiating, which elements in the TR box are energized?

Back 51

C. Both the TR and ATR tubes.

Front 52

A keep-alive voltage is applied to:

Back 52

C. The TR tube.

Front 53

The triggering section is also known as the:

Back 53

D. Synchronizer

Front 54

The timer circuit:

Back 54

D. All of the above.

PRR, range markers, signals on CRT.

Front 55

Pulse RADARs require precise timing for their operation. Which type circuit below might best be used to provide these accurate timing pulses?

Back 55

A. Single-swing blocking oscillator.

Front 56

Unblanking pulses are produced by the timer circuit. Where are they sent?

Back 56

C. CRT

Front 57

An advantage of resonant charging is that it:

Back 57

C. Reduces the high-voltage power supply requirements.

Front 58

The characteristics of a field-effect transistor (FET) used in a modern RADAR switching power supply can be compared as follows:

Back 58

B. "On" state compares to a pure resistor. "Off" state compares to a mechanical relay.

Front 59

Which of the following characteristics are true of a power MOSFET used in a RADAR switching supply?

Back 59

B. High input impedence; failure mode can be gate punch-through

Front 60

RADAR receivers are similar to:

Back 60

D. Microwave receivers

Front 61

What is the main difference between an analog and digital receiver?

Back 61

B. The presence of decision circuitry to distinguish between "on" and "off" signal levels.

Front 62

An RF mixer has what purpose in a RADAR system?

Back 62

B. Converts a low-level signal to a different frequency.

Front 63

The error voltage from the discriminator is applied to the:

Back 63

A. Repeller (reflector) of the klystron.

Front 64

In a RADAR unit, the local oscillator is a:

Back 64

B. Klystron

Front 65

What device(s) could be used as the local oscillator in a RADAR receiver?

Back 65

C. Klystron and a Gunn diode.

Front 66

The klystron local oscillator is constantly kept on frequency by:

Back 66

B. The Automatic Frequency Control circuit.

Front 67

The usual intermediate frequency of a shipboard RADAR unit is:

Back 67

C. 30 or 60 MHz

Front 68

The I.F. Amplifier bandwidth is:

Back 68

A. Wide for short ranges and narrow for long ranges.

Front 69

A logarithmic IF amplifier is preferable to a linear IF amplifier in a RADAR receiver because it:

Back 69

D. Has a greater dynamic range.

Front 70

The high-gain IF amplifiers in a RADAR receiver may amplify a 2 microvolt input signal to an output level of 2 volts. This amount of amplification represents a gain of:

Back 70

C. 120 db.

Front 71

Which of the following statements is correct?

Back 71

C. The video amplifier is located between the I.F. amplifier and the display system.

Front 72

Video amplifiers in pulse RADAR receivers must have a broad bandwidth because:

Back 72

A. Weak pulses must be amplified.

Front 73

In video amplifiers, compensation for the input and output stage capacitances must be accomplished to prevent distoring the video pulses. This compensation is normally accomplished by connecting:

Back 73

D. An inductor in series with the input capacitance and an inductor in parallel with the output capacitance.

Front 74

The AFC system is used to:

Back 74

B. Control the frequency of the klystron.

Front 75

A circuit used to develop AFC voltage in a RADAR receiver is called the:

Back 75

D. Discriminator.

Front 76

An AFC system keeps the receiver tuned to the transmitted signal by varying the frequency of the:

Back 76

C. Local oscillator

(Klystron)

Front 77

The STO circuit:

Back 77

B. Decreases sea return on the PPI scope

(Stuff To Close)

Front 78

Sea return is:

Back 78

C. The reflection of RADAR signals from nearby waves.

Front 79

Sea clutter on the RADAR scope cannot be effectively reduced using front panel controls. What circuit would you suspect is faulty?

Back 79

A. Sensitivity Time Control (STC) circuit.

Front 80

Prior to making "power-on" measurements on a switching power supply, you should be familiar with the supply because of the folowing:

Back 80

B. If it does not use a line isolation transformer you may destroy the supply with grounded test equipment.

Front 81

With regard to the comparator shown in Fig. 8C11, the imnput is a sinusoid. Nominal high level output of the comparator is 4.5 volts. Choose the most correct statement regarding the input and output.

Back 81

A. The leading edge of the output waveform occurs 180 degrees after positive zero crossing of the input waveform.

Front 82

When monitoring the gate voltage of a power MOSFET in the switching power supply of a moderns RADAR, you would expect to see the gate voltage change from "low" to "high" by how much?

Back 82

C. Greater than 2 volts.

Front 83

The nominal output high of the comparator shown in Fig. 8C11 is 4.5 volts. Choose the most correct statement which describes the trip points.

Back 83

D. Upper trip point is +1.285 volts. Lower trip point is -1.285 volts.

Front 84

Noise can appear on the LCD as:

Back 84

A. Erratic video and sharp changes in intensity.

Front 85

RADAR interference on a communications receiver appears as:

Back 85

D. A steady tone.

Front 86

In a RADAR receiver the most common types of interference are?

Back 86

A. Weather and sea return.

Front 87

Noise can:

Back 87

C. Mask small targets.

Front 88

The MTI circuit:

Back 88

B. Is a filter, which blocks out stationary targets, allowing only moving targets to be detected.

Front 89

Where is a RF attenuator used in a RADAR unit?

Back 89

C. Between the magnetron and the AFC section of the receiver.

Front 90

When the receiver employs an MTI circuit:

Back 90

B. Only moving targets will be displayed.

Front 91

Voltages used in CRT anode circuits are in what range of value?

Back 91

B. 10-50 kV.

Front 92

The purpose of the aquadog coating on the CRT is:

Back 92

D. All of the above

Protect electrons, secondary anode, attract emissions.

Front 93

What are the usual input signals to the video amplifier?

Back 93

D. All of the above

Video, fixed rings, variable rings.

Front 94

Which of the following would not normally be an input to the video amplifier?

Back 94

C. Resolver signal.

Front 95

The main purpose of the sweep generator is to provide:

Back 95

D. The drive signal to the sweep amplifier.

Front 96

The circuit that develops timing signals is called the:

Back 96

B. Synchronizer

Front 97

Which of the following functions is not affected by the timing circuit?

Back 97

A. Resolver output

Front 98

The syncronizer primarily affects the following circuit or functions:

Back 98

C. Modulator

Front 99

The output from the syncronizer usually consists of a:

Back 99

B. Pulse or square wave.

Front 100

Accurate range markers must be developed using very narrow pulses. A circuit that could be used to provide these high-quality pulses for the CRT is a:

Back 100

D. Blocking oscillator

Front 101

Range markers are determined by:

Back 101

C. The timer

Front 102

A gated LC oscillator, operating at 27 kHz, is being used to develop range markers. If each cycle is converted to a range mark, the range between markers will be:

Back 102

A. 3 nautical miles.

Front 103

What would be the frequency of a range ring marker oscillator generating range rings at 10 nautical miles intervals?

Back 103

D. 8 kHz

Front 104

The variable range marker signal is normally fed to the input of the:

Back 104

C. Video amplifier.

Front 105

The purpose of the variable range marker is to:

Back 105

A. Provide an accurate means of determining the range of a moving target.

Front 106

How is the variable range marker usually adjusted for accuracy?

Back 106

D. The minimum and maximum ranges are aligned with the matching fixed range ring.

Front 107

The purpose of the Electronic Bearing Line is to:

Back 107

B. Measure the bearing of a specific target.

Front 108

Bearing information from the gyro is used to provide the following:

Back 108

C. Vessel's own heading.

Front 109

Which of the following statements about "true bearing" is correct?

Back 109

B. True North is at the top of the screen and the heading flasher indicates the vessel's course.

Front 110

While troubleshooting a memory problem in a raster scan RADAR, you discover that the "REFRESH" cycle is not operating correctly. What type of memory circuit are you working on?

Back 110

B. DRAM

Front 111

How does the dual memory function reduce sea clutter?

Back 111

A. Successive sweeps are digitized and compared. Only signals appearing in both sweeps are displayed.

Front 112

How many sequential memory cells with target returns are required to display the target?

Back 112

B. 2

Front 113

The ship's speed indication on the ARPA display can be set manually, but does not change with changes in the vessel's speed. What other indication would point to a related equipment failure?

Back 113

B. "LOG OUT" is displayed on the ARPA indicator.

Front 114

What does the term ARPA/CAS refer to?

Back 114

C. The device which acquires and tracks targets that are displayed on the RADAR indicator's CRT.

Front 115

What is the purpose or function of the "Trial Mode" used in most ARPA equipment?

Back 115

C. It is used to allow results of proposed maneuvers to be assessed.

Front 116

The display power supply provides the following:

Back 116

B. 5 volts DC for logic circuits and +-12 volts DC for analog and sweep circuits.

Front 117

In a display system power supply what is the purpose of the chopper?

Back 117

A. It acts as an electronic switch between the raw DC output and the inverter.

Front 118

In a display system power supply, what is the purpose of the inverter?

Back 118

D. Produces the pulsed DC input voltage to the power transformer.

Front 119

What would be a common switching frequency for a display system power supply?

Back 119

A. 18 kHz

Front 120

The heading flash is a momentary intensification of the sweep line on the PPI presentation. Its function is to:

Back 120

C. Inform the operator of the dead-ahead position on the PPI scope.

Front 121

The major advantage of digitally processing a RADAR signal is:

Back 121

B. Enhancement of weak target returns.

Front 122

The output of an RC integrator, when driven by a square wave with a period of much less than one time constant is a:

Back 122

D. Triangle wave

Front 123

Slotted waveguide arrays, when fed from one end exhibit:

Back 123

A. Frequency scan.

Front 124

A typical shipboard RADAR antenna is a:

Back 124

B. Slotted waveguide array.

Front 125

Good bearing resolution largely depends upon:

Back 125

D. A narrow antenna beam in the horizontal plane.

Front 126

The impedance total (Z0) of a transmission line can be calculated by Z0 = Square of L/C when L and C are known. When a section of transmission line contains 250 microhenries of L and 1000 picofarads of C, its impedance total (Z0) will be:

Back 126

C. 500 ohms.

Front 127

If long-length transmission lines are not properly shielded and terminated:

Back 127

B. Communications receiver interference might result.

Front 128

A certain length of transmission line has a characteristic impedance of 72 ohms. If the line is cut at its center, each half of the transmission line will have a Z0 of:

Back 128

C. 72 ohms.

Front 129

Standing waves on a transmission line may be an indication that:

Back 129

D. Some of the energy is not absorbed by the load.

Front 130

The position of the PPI scope sweep must indicate the position of the antenna. The sweep and antenna positions are frequently kept in syncrhonization by the use of:

Back 130

A. Synchro systems

Front 131

On a basic syncrho system, the angular information is carried on the:

Back 131

B. Stator Lines.

Front 132

What is the most common type of antenna position indicating device used in modern RADARs?

Back 132

A. Resolvers

Front 133

An antenna synchro transmitter is composed of the following:

Back 133

B. Two rotor and three stator windings.

Front 134

A microwave transmission line constructed of a center conductor suspended between parallel conductive ground planes is called:

Back 134

C. Stripline

Front 135

A waveguide is used at RADAR microwave frequencies because:

Back 135

D. It has lower transmission losses than other feedline types.

Front 136

Waveguide theory is based on the principals of:

Back 136

C. Skin effect and use of 1/4 wave stubs.

Front 137

How is the signal removed from a waveguide or magnetron?

Back 137

B. With a thin wire called a J-Hook.

Front 138

A rotary joint is used to:

Back 138

C. Connect a stationary waveguide to the antenna array.

Front 139

A right-angle bend in an X-band waveguide must have a radius greater than:

Back 139

D. Two inches.

Front 140

To insert RF energy into or extract RF energy from a waveguide, which of the following would not be used?

Back 140

A. Coupling capacitance.

Front 141

When you examine the RADAR you notice that there is no target video in the center of the CRT. The blank spot gets smaller in diameter as you increase the range scale. What operator front panel control could be misadjusted?

Back 141

B. Sensitivity Time Control (STC)

Front 142

Range rings on the PPI indicator are oval in shape. Which circuit would you suspect is faulty?

Back 142

D. Sweep generation circuit.

Front 143

What would be the most likely defective area when thee is no target video in the center of the CRT and the blank spot gets smaller in diameter as your range scale is increased?

Back 143

A. The TR (TRL) Cell.

Front 144

In a RADAR using digital video processing, a bright, wide ring appears at fixed distance from the center of the display on all digital ranges. The transmitter is operating normally. What receiver circuit would you suspect is causing the problem?

Back 144

B. Video storage RAM or shift register.

Front 145

A circuit card in a RADAR system has just been replaced with spare card. You notice the voltage level at point E in Fig. 8F12 is negative 4.75 volts when the inputs are all at 5 volts. The problem is:

Back 145

D. The 50 K resistor has been mistakenly replaced with a 25 K resistor.

Front 146

The RADAR display has sectors of solid video (spoking). What would be the first thing to check?

Back 146

C. For interference from nearby ships.

Front 147

In the circuit contained in Fig. 8F12, there are 5 volts present at points B and C, and there are zero volts present at points A and D. What is the voltage at point E?

Back 147

A. -1.5 volts.

Front 148

If the TR tube malfunctions:

Back 148

B. The receiver might be damaged.

Front 149

In a RADAR unit, if the crystal mixer becomes defective, replace the:

Back 149

C. The crystal and the TR tube.

Front 150

An increase in magnetron current that coincides with a decrease in power output is an indication of what?

Back 150

D. The external magnet weakening

Front 151

A high magnetron current indicates a/an:

Back 151

C. Defective external magnetic field.

Front 152

Low or no mixer current could be caused by:

Back 152

D. All of the above

Misadjustment, TR failure, diode degratation.

Front 153

Loss of distant targets during and immediately after wet weather indicates:

Back 153

A. A leak in waveguide or rotary joint.

Front 154

In a marine RADAR set, a high VSWR is indicated at the magnetron output. The waveguide and rotary joint appear to be functioning properly. What component may be malfunctioning?

Back 154

D. The waveguide array termination

Front 155

An increase in the deflection on the magnetron current meter could likely be caused by:

Back 155

C. A decrease of the magnetic field strength.

Front 156

The echo box is used for:

Back 156

B. Testing and tuning of the RADAR unit by providing artificial targets.

Front 157

What sould be done to the interior surface of a waveguide in order to minimize signal loss?

Back 157

C. Keep it as clean as possible.

Front 158

Which of the following is the most useful instrument for RADAR servicing?

Back 158

A. Oscilloscope.

Front 159

Why should long horizontal runs of waveguide be avoided?

Back 159

D. To prevent accumulation of condensation.

Front 160

In a RADAR system, waveguides should be installed:

Back 160

B. As straight as possible to reduce distortion.

Front 161

What is the most important factor to consider in locating the antenna?

Back 161

C. The antenna is in a location that is not shadowed by other structures.

Front 162

Choose the most correct statement with respect to component damage from electrostatic discharge:

Back 162

D. ESD damage may cause immediate circuit failures, but may also cause failures much later at times when the RADAR set is critically needed.

Front 163

Prior to removing, servicing or making measurements on any solid state circuit boards from the RADAR set, the operator should ensure that:

Back 163

A. The proper work surfaces and ESD grounding straps are in place to prevent damage to the boards from electrostatic discharge.