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AAS 1 > Aircraft Antenna Considerations > Flashcards

Aircraft Antenna Considerations Flashcards

1
Q

An antenna is the component of radio systems that is used to:

A

send or receive a radio signal

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2
Q

What does the antenna release in the form of an electromagnetic field to be sent to a distant receiver?

A

RF energy

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3
Q

What does the receiving antenna do?

A

absorbs the transmitted RF energy

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4
Q

Most aviation antennas are variations of three basic antennas:

A

Marconi (Macaroni)
Hertzian (Hershies)
Yagi-Uda (Yakisoba)

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5
Q

When used in line of sight applications, how do the antennas work best?

A

when the transmitting and receiving antennas are polarized the same

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6
Q

What is an Isotropic Radiator?

A

a one-dimensional point in space that transmits energy equally in all directions in a spheroid pattern with 100% efficiency

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7
Q

A Hertzian antenna is also known as:

A

a dipole and consists of two 1/4 wires placed end to end

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8
Q

Hertzian antennas radiate well where?

A

In directions perpendicular to the antenna, however they do not radiate at all off the wire tips

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9
Q

Because the radiated energy emitted from a hertzian antenna is concentrated broadside to the wire:

A

this type of antenna exhibits 2.1 db of gain when compared to an isotropic radiator

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10
Q

What systems are Hertzian antennas used in?

A

VHF Omnirange, localizer, and glideslope

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11
Q

How are Hertzian antennas used on aircraft polarized? (which direction)

A

Horizontally

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12
Q

Marconi antennas are commonly referred to as:

A

a vertical antenna

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13
Q

The vast majority of Marconi type antennas are polarized:

A

Vertically

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14
Q

The Marconi antenna radiates well where?

A

in all directions and considered to be an omnidirectional antenna. does not radiate well off the tips

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15
Q

What may be added when a marconi antenna is mounted on a tower?

A

A counterpoise

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16
Q

What does a counterpoise do?

A

it acts as ground and as the second 1/4 of the radiating element

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17
Q

Marconi antennas are used in aircraft with what systems?

A

VHF and HF communications, transponders, DME, GPS, and marker beacon systems

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18
Q

The Yagi-uda antenna is considered to be what type of antenna?

A

a unidirectional antenna.
This type focuses a majority of the radiation pattern in a single pattern

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19
Q

The yagi-uda antenna consists of a dipole element called:

A

the driven element

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20
Q

What are added to a yagi-uda antenna?

A

directors and reflectors

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21
Q

Where do Directors focus the energy?

A

toward the intended single direction

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22
Q

What do Reflectors do to the energy?

A

bounce the energy back in the intended direction

23
Q

Directors and Reflectors are known as:

A

parasitic elements, since they have no direct electrical connection to the antenna

24
Q

In comparison to the Hertzian antenna, the Yagi-uda antenna will exhibit how much gain?

A

8 dB due to the energy being focused in one direction

25
Q

Antennas require what in order to receive and transmit the desired frequency?

A

they required a certain length. the length of the antenna will be equal to the frequency.

26
Q

What does a loading coil do?

A

electronically lengthens an antenna while keeping it physically short

27
Q

A loop antenna has the ability to what?

A

determine the direction a signal is coming from. This is known as a Directional Antenna

28
Q

How does a loop antenna (or directional antenna) determine the direction of a frequency’s origin?

A

Signals are received at different strengths between coils inside of the antenna. The receiver then uses those differing strengths to determine the directions it’s coming from

29
Q

Where can loop antennas on aircraft be found?

A

in the ADF and lightning detection systems

30
Q

When installing antennas on aircrafts, they must be:

A

Structurally secure
Free from obstruction
Sealed from harsh environment
Free from interference from other antennas

31
Q

What does STC stand for?

A

Supplemental Type Certificate

32
Q

Some antennas, such as the Marconi and Hertzian, are:

A

Passive (non-powered)

33
Q

What are Active (powered) antennas?

A

antennas that require the additional installment of a power supply and amplifiers or filters

34
Q

What does TSO stand for?

A

Transportation Safety Office

35
Q

To ensure an airworthy antenna installation, consult the technical specifications for:

A

Obstructions
Spacing
Noise reception
Vibration
Flutter
Static System Interference

36
Q

Composite aircraft may need what?

A

a counterpoise

37
Q

In some composite aircraft, a layer of:

A

conductive material may be a part of the outside structure

38
Q

In the case of the aircraft having an outer layer of conductive material, the technician must:

A

ensure that the base of the antenna makes contact with the conductive surface

39
Q

If the aircraft is not made of conductive material then:

A

an aluminum grounding plate may be used as a counterpoise

40
Q

What does DER stand for?

A

Designated Engineering Representative

41
Q

What might a technician have to calculate?

A

Dynamic load due to aerodynamic drag

42
Q

Antennas should be mounted:

A

on a flat surface whenever possible

43
Q

What is used if the curvature is too great for a gasket to seal the antenna?

A

A Mounting Saddle

44
Q

How do you prevent moisture when mounting an antenna?

A

fill in any gaps with sealant

45
Q

When troubleshooting a transmitter, it begins with:

A

a visual inspection

46
Q

Reflected power will create what?

A

standing waves

47
Q

What describes standing waves?

A

power dissipating within the transmission line

48
Q

How do you measure standing waves?

A

calculate the voltage standing wave ratio (VSWR)

49
Q

What does VSWR stand for?

A

Voltage Standing Wave Ratio

50
Q

What is VSWR?

A

a comparison of the forward moving energy and reflected energy
(Standing Waves)

51
Q

An excellent antenna has a VSWR of:

A

1.2:1 or less

52
Q

Not only does a high VSWR create transmitter loss, but also creates:

A

a reception loss that increases as VSWR increases

53
Q

What will a through line wattmeter not work for?

A

antennas connected to receivers

54
Q

What is a duplexer?

A

a component that allows more than one receiver to share the same antenna

AAS 1 (25 decks)

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