Subelement E – Antenna Systems

Question 1

Slotted waveguide arrays, when fed from one end exhibit:
A. Frequency scan.
B. High VSWR.
C. Poor performance in rain.
D. A narrow elevation beam.

Answer 1

A

Question 2

A typical shipboard RADAR antenna is a:
A. Rotary parabolic transducer.
B. Slotted waveguide array.
C. Phased planar array.
D. Dipole.

Answer 2

B

Question 3

Good bearing resolution largely depends upon:
A. A high transmitter output reading.
B. A high duty cycle.
C. A narrow antenna beam in the vertical plane.
D. A narrow antenna beam in the horizontal plane.

Answer 3

D

Question 4

The center of the transmitted lobe from a slotted waveguide array is:
A. Several degrees offset from a line perpendicular to the antenna.
B. Perpendicular to the antenna.
C. Maximum at the right hand end.
D. Maximum at the left hand end.

Answer 4

A

Question 5

How does antenna length affect the horizontal beamwidth of the transmitted signal?
A. The longer the antenna the wider the horizontal beamwidth.
B. The longer the antenna the narrower the horizontal beamwidth.
C. The horizontal beamwidth is not affected by the antenna length.
D. None of the above.

Answer 5

B

Question 6

What is the most common type of RADAR antenna used aboard commercial maritime vessels?
A. Parabolic.
B. Truncated parabolic.
C. Slotted waveguide array.
D. Multi-element Yagi array.

Answer 6

C

Question 7

The VSWR of a microwave transmission line device might be measured using:
A. A dual directional coupler and a power meter.
B. A network analyzer.
C. A spectrum analyzer.
D. A dual directional coupler, a power meter, and a network analyzer.

Answer 7

D

Question 8

The impedance total (ZO) of a transmission line can be calculated by ZO = √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 (ZO) will be:
A. 50 ohms.
B. 250 ohms.
C. 500 ohms.
D. 1,000 ohms.

Answer 8

C

Question 9

If long-length transmission lines are not properly shielded and terminated:
A. The silicon crystals can be damaged.
B. Communications receiver interference might result.
C. Overmodulation might result.
D. Minimal RF loss can result.

Answer 9

B

Question 10

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 ZO of:
A. 36 ohms.
B. 144 ohms.
C. 72 ohms.
D. The exact length must be known to determine Zo.

Answer 10

C

Question 11

Standing waves on a transmission line may be an indication that:
A. All energy is being delivered to the load.
B. Source and surge impedances are equal to ZO and ZL.
C. The line is terminated in impedance equal to ZO.
D. Some of the energy is not absorbed by the load.

Answer 11

D

Question 12

What precautions should be taken with horizontal waveguide runs?
A. They should be sloped slightly downwards at the elbow and a small drain hole drilled in the elbow.
B. They should be absolutely level.
C. They should not exceed 10 feet in length.
D. None of the above.

Answer 12

A

Question 13

The position of the PPI scope sweep must indicate the position of the antenna. The sweep and antenna positions are frequently kept in synchronization by the use of:
A. Synchro systems.
B. Servo systems.
C. DC positioning motors.
D. Differential amplifiers.

Answer 13

A

Question 14

On a basic synchro system, the angular information is carried on the:
A. DC feedback signal.
B. Stator lines.
C. Deflection coils.
D. Rotor lines.

Answer 14

B

Question 15

What is the most common type of antenna position indicating device used in modern RADARs?
A. Resolvers.
B. Servo systems.
C. Synchro transmitters.
D. Step motors.

Answer 15

A

Question 16

Which of the following statements about antenna resolvers is correct?
A. Most resolvers contain a rotor winding and a delta stator winding.
B. Resolvers consist of a two rotor windings and two stator windings that are 90 degrees apart.
C. The basic resolver contains a rotor winding and two stator windings that are 90 degrees apart.
D. Resolvers consist of a “Y” connected rotor winding and a delta connected stator winding.

Answer 16

C

Question 17

An antenna synchro transmitter is composed of the following:
A. Three rotor and two stator windings.
B. Two rotor and three stator windings.
C. Three rotor and three stator windings.
D. A single rotor and 3 stator windings.

Answer 17

B

Question 18

RADAR antenna direction must be sent to the display in all ARPAs or RADAR systems. How is this accomplished?
A. 3-phase synchros.
B. 2-phase resolvers.
C. Optical encoders.
D. Any of the above.

Answer 18

D

Question 19

Waveguides can be constructed from:
A. Brass.
B. Aluminum.
C. Copper.
D. All of the above.

Answer 19

D

Question 20

A microwave transmission line constructed of a center conductor suspended between parallel conductive ground planes is called:
A. Microstrip.
B. Coax.
C. Stripline.
D. Waveguide.

Answer 20

C

Question 21

Waveguide theory is based upon:
A. The movement of an electromagnetic field.
B. Current flow through conductive wires.
C. Inductance.
D. Resonant charging.

Answer 21

A

Question 22

A waveguide is used at RADAR microwave frequencies because:
A. It is easier to install than other feedline types.
B. It is more rugged than other feedline types.
C. It is less expensive than other feedline types.
D. It has lower transmission losses than other feedline types.

Answer 22

D

Question 23

Waveguide theory is based on the principals of:
A. Ohm’s Law.
B. High standing waves.
C. Skin effect and use of ¼ wave stubs.
D. None of the above.

Answer 23

C

Question 24

How is the signal removed from a waveguide or magnetron?
A. With a thin wire called a T-hook.
B. With a thin wire called a J-Hook.
C. With a coaxial connector.
D. With a waveguide flange joint.

Answer 24

B

Question 25

A rotary joint is used to:
A. Couple two waveguides together at right angles.
B. Act as a switch between two waveguide runs.
C. Connect a stationary waveguide to the antenna array.
D. Maintain pressurization at the end of the waveguide.

Answer 25

C

Question 26

Resistive losses in a waveguide are very small because:
A. The inner surface of the waveguide is large.
B. The inner surface of the waveguide is small.
C. The waveguide does not require a ground connection.
D. The heat remains in the waveguide and cannot dissipate.

Answer 26

A

Question 27

A right-angle bend in an X-band waveguide must have a radius greater than:
A. Three inches.
B. Six inches.
C. One inch.
D. Two inches.

Answer 27

D

Question 28

To insert RF energy into or extract RF energy from a waveguide, which of the following would not be used?
A. Coupling capacitance.
B. Current loop.
C. Aperture window.
D. Voltage probe.

Answer 28

A

Question 29

The following is true concerning waveguides:
A. Conduction is accomplished by the polarization of electromagnetic and electrostatic fields.
B. Ancillary deflection is employed.
C. The magnetic field is strongest at the center of the waveguide.
D. The magnetic field is strongest at the edges of the waveguide.

Answer 29

D

Question 30

At microwave frequencies, waveguides are used instead of conventional coaxial transmission lines because:
A. They are smaller and easier to handle.
B. They have considerably less loss.
C. They are lighter since they have hollow centers.
D. Moisture is never a problem with them.

Answer 30

B