Aircraft Antenna Considerations

Question 1

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

Answer 1

send or receive a radio signal

Question 2

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

Answer 2

RF energy

Question 3

What does the receiving antenna do?

Answer 3

absorbs the transmitted RF energy

Question 4

Most aviation antennas are variations of three basic antennas:

Answer 4

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

Question 5

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

Answer 5

when the transmitting and receiving antennas are polarized the same

Question 6

What is an Isotropic Radiator?

Answer 6

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

Question 7

A Hertzian antenna is also known as:

Answer 7

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

Question 8

Hertzian antennas radiate well where?

Answer 8

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

Question 9

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

Answer 9

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

Question 10

What systems are Hertzian antennas used in?

Answer 10

VHF Omnirange, localizer, and glideslope

Question 11

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

Answer 11

Horizontally

Question 12

Marconi antennas are commonly referred to as:

Answer 12

a vertical antenna

Question 13

The vast majority of Marconi type antennas are polarized:

Answer 13

Vertically

Question 14

The Marconi antenna radiates well where?

Answer 14

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

Question 15

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

Answer 15

A counterpoise

Question 16

What does a counterpoise do?

Answer 16

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

Question 17

Marconi antennas are used in aircraft with what systems?

Answer 17

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

the driven element

Question 20

What are added to a yagi-uda antenna?

Answer 20

directors and reflectors

Question 21

Where do Directors focus the energy?

Answer 21

toward the intended single direction

Question 22

What do Reflectors do to the energy?

Answer 22

bounce the energy back in the intended direction

Question 23

Directors and Reflectors are known as:

Answer 23

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

Question 24

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

Answer 24

8 dB due to the energy being focused in one direction

Question 25

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

Answer 25

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

Question 26

What does a loading coil do?

Answer 26

electronically lengthens an antenna while keeping it physically short

Question 27

A loop antenna has the ability to what?

Answer 27

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

Question 28

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

Answer 28

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

Question 29

Where can loop antennas on aircraft be found?

Answer 29

in the ADF and lightning detection systems

Question 30

When installing antennas on aircrafts, they must be:

Answer 30

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

Question 31

What does STC stand for?

Answer 31

Supplemental Type Certificate

Question 32

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

Answer 32

Passive (non-powered)

Question 33

What are Active (powered) antennas?

Answer 33

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

Question 34

What does TSO stand for?

Answer 34

Transportation Safety Office

Question 35

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

Answer 35

Obstructions Spacing Noise reception Vibration Flutter Static System Interference

Question 36

Composite aircraft may need what?

Answer 36

a counterpoise

Question 37

In some composite aircraft, a layer of:

Answer 37

conductive material may be a part of the outside structure

Question 38

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

Answer 38

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

Question 39

If the aircraft is not made of conductive material then:

Answer 39

an aluminum grounding plate may be used as a counterpoise

Question 40

What does DER stand for?

Answer 40

Designated Engineering Representative

Question 41

What might a technician have to calculate?

Answer 41

Dynamic load due to aerodynamic drag

Question 42

Antennas should be mounted:

Answer 42

on a flat surface whenever possible

Question 43

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

Answer 43

A Mounting Saddle

Question 44

How do you prevent moisture when mounting an antenna?

Answer 44

fill in any gaps with sealant

Question 45

When troubleshooting a transmitter, it begins with:

Answer 45

a visual inspection

Question 46

Reflected power will create what?

Answer 46

standing waves

Question 47

What describes standing waves?

Answer 47

power dissipating within the transmission line

Question 48

How do you measure standing waves?

Answer 48

calculate the voltage standing wave ratio (VSWR)

Question 49

What does VSWR stand for?

Answer 49

Voltage Standing Wave Ratio

Question 50

What is VSWR?

Answer 50

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

Question 51

An excellent antenna has a VSWR of:

Answer 51

1.2:1 or less

Question 52

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

Answer 52

a reception loss that increases as VSWR increases

Question 53

What will a through line wattmeter not work for?

Answer 53

antennas connected to receivers

Question 54

What is a duplexer?

Answer 54

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