DME

Question 1

How does the DME measure distance?

Answer 1

Uses time

Question 2

What does DME provide?

Answer 2

Slant Range (distance), Ground Speed(KTS), Time to Station

Question 3

Who is interrogating the DME?

Answer 3

The Aircraft is interrogating, and the DME is replying

Question 4

How long does it take for 1NM?

Answer 4

12.36uS round trip (6.18uS one way)

Question 5

Why are the DME pulses a trapezoidal shape?

Answer 5

For better propagation of the ANT. The better the propagation, the greater than range with low power.

Question 6

How many miles is the DME good for?

Answer 6

100-200miles

Question 7

How large are the pulses of a DME?

Answer 7

3.5uS

Question 8

What is the pulse spacing for an X channel?

Answer 8

12uS(aircraft)

Question 9

If the pulse spacing is 36uS(aircraft), what channel are we in?

Answer 9

Y channel

Question 10

How many DME channels are there?

Answer 10

200 (100X and 100Y)

Question 11

What is the Tx range?

Answer 11

1041MHz - 1150MHz

Question 12

What is the Rx range?

Answer 12

978MHz-1213MHz

Question 13

How do you know if the frequency is on an X or a Y channel?

Answer 13

X ends in a 00

Y ends in a .05

Question 14

How many MHz is the change from Tx to Rx?

Answer 14

63MHz

Question 15

What is the spacing on a Y channel Rx?

Answer 15

30uS(ground)

Question 16

How long is the ground station delay and what is it for?

Answer 16

50uS used for nearby navigation to give time to decode and reply

Question 17

What are squitter pulses and how many pp/s does it send out?

Answer 17

To make standby DMEs go back to working, sends out 2700pp/s. The closer the aircraft, squitter turns to reply

Question 18

What is the PRF for search mode?

Answer 18

100pp/s

Question 19

What is the PRF in track mode?

Answer 19

25pp/s

Question 20

How many aircrafts can the DME ground station handle?

Answer 20

100 aircrafts

Question 21

What is a JITTER rate?

Answer 21

Unique PP (gap/timing is different for each aircraft). Uses noise. Picks out its specific replies.

Question 22

What are the frequency increments?

Answer 22

1MHz steps

Question 23

What is a quick way to test the sensitivity of the DME?

Answer 23

Turn on audio, adjust the attenuator until morse is just barely heard, turn off audio, then will automatically lock on

Question 24

What is the DME Audio ID?

Answer 24

Ground stations sends out a 3 letter morse code every 30s. During those 30s no replies(no lock on).

Question 25

What is the PRF of the Audio ID?

Answer 25

1350pp/s, all equal.

Question 26

The DME sensitivity is also know as?

Answer 26

Acquisition Sensitivity

Question 27

When testing receiver sensitivity what dBm should we be looking for?

Answer 27

-82dBm

Question 28

When more than 100 interrogations are being sent to the DME, what happens to the AOC?

Answer 28

The ground station will reduce its sensitivity

Question 29

What is the aircraft DME Memory mode?

Answer 29

The DME continues tracking for 10-15s to prevent it from going back into search mode`

Question 30

When you click Hold mode, what happens?

Answer 30

You can select a new VOR/LOC frequency while still tracking the old one