RNAV 2nd Lesson

Question 1

Harmonics

Answer 1

Two sin waves inside a sin wave

Question 2

On an omni aerial, as distance doubles…

Answer 2

Power is 1/4 of original value

Question 3

In a polar diagram, field strength is

^(donut or toroidal shape)

Answer 3

The same in all directions

Question 4

Marconi is a dipole at

Answer 4

1/4 wavelength

Question 5

For Max efficiency, the aerial length should be

Answer 5

1/2 Wavelength

Question 6

Directional aerial may have a

Answer 6

Parasite element - the reflector. Puts signal in right direction, if had gone wrong way.

Question 7

Parabolic radar is feeded info by a

Answer 7

Wave guide

Question 8

Parabolic radar, types of frequencies:

Answer 8

VHF & SHF

Question 9

Parabolic radar features =

Answer 9

Side lobes = waste of energy

Question 10

A slotted scanner/ planner array is a …. produces?

Answer 10

Flat plate. Produces very narrow beams. Fewer side lobe = less energy used.

Question 11

Phase array antenna consists of

Answer 11

Lots of little radars. Produces vertical fan beam.

And can be electronically steered.

Changes the phase - which allows a change of direction.

Used with SECONDARY SURVEILLANCE RADAR.

Question 12

Helical antenna

Answer 12

Have a circular polarisation.

Best received by helical aerials - mobile phone & GPS

Question 13

Radio propagation - from one antenna to another. The process

Answer 13

Ground wave follows ground. Splits into surface wave (VLF, LF, MF) and Space Wave - open space (VHF & higher). This then carries on as a space wave or travels to ground to become a ground reflective wave.
And the Skywave goes up to the ionosphere, where it is reflected back to the ground.

Question 14

Everything is a ground wave except a

Answer 14

Sky wave

Question 15

Attenuation is the

Answer 15

Gradual loss of signal strength through a medium.

Question 16

Ionosphere attenuation will

Answer 16

Reduce when frequency increases

Question 17

Atmospheric attenuation is…

But…

Answer 17

Low in the lower atmosphere.

But is only significant after 1 GHZ

Question 18

Surface attenuation,

Answer 18

When frequency goes up, attenuation goes up. Which also means dead space will increase, reducing the surface wave.

Question 19

Surface attenuation is also

Answer 19

Worse over land than the sea. And is the worst over the ice caps.

Question 20

The ionosphere layers consist of:

Answer 20

D E F(f1 & f2)

Question 21

D layer has the …. and

Answer 21

Greatest attenuation & disappears at night.

Question 22

At night (with skywave)

Answer 22

You get greater distances with the same critical angle

Question 23

Optimum frequency gives the

Answer 23

First returning wave exactly to the receiver .

Question 24

MUF stands for

Answer 24

Max. Usable frequency

Question 25

Optimum distance is

Answer 25

100NM

Question 26

Higher frequency is better because of

Answer 26

Less static interference

Question 27

The lowest usable frequency is limited to

Answer 27

The static

Question 28

Minimum skip distance =

Answer 28

Surface wave distance + dead space

Question 29

F1 & F2 make up the….

Located …. up

Answer 29

Appleton layer

225 km up.

Question 30

F layer is the

D layer is the

Answer 30

Strongest

Weakest

Question 31

F1 & F2 give

Answer 31

Refraction

Question 32

E&D GIVE

Answer 32

Attenuation

Question 33

E layer is called the …

Located…

Answer 33

Kennelly - Heaviside layer

125km up

Question 34

D layer located…. up

Answer 34

75km up

Question 35

Sun up

Sun down

Answer 35

Fq up

Fq down

Question 36

Line of sight comms are limited to

Answer 36

The curvature of the earth

Question 37

Line of sight is also greatly affected by the

Answer 37

Height of the receiver & transmitter

Question 38

Transmitter in formula

Answer 38

Tx

IN FEET

Question 39

Receiver in formula

Answer 39

Rx

IN FEET

Question 40

Maximum Theoretical range (MTR) = in formula:

Answer is in:

Answer 40

1.23 X ( (sqrHtofTx) + (sqrHtofRx) )

NM