Week 1

Question 1

What is the audio that comes from comm radios/nav equipment for identification?

Answer 1

Received Audio

Question 2

What is the Received audio output impedance for headphones and speakers?

Answer 2

500-600ohms for headphones

3.2-8ohms for speaker

Question 3

What is the audio that is heard on headphones and is a conversation between crew members? Can either be ICS, VOX, or PTT

Answer 3

Interphone audio

Question 4

What is the interphone audio output impedance?

Answer 4

500ohms

Question 5

What is the audio that is pretty much feedback and is the audio heard on the headphones of crew while tx

Answer 5

Side tone audio

Question 6

Is the side tone audio level adjustable by the pilot?

Answer 6

No

Question 7

Where is the side tone audio adjustable?

Answer 7

Radio bench

Question 8

This audio is low level, 0.15-0.25VAC that is created by speaking into a mic

Answer 8

Microphone audio

Question 9

In microphone audio, what changes are you looking for in the line?

Answer 9

Change in voltage or resistance

Question 10

When testing what should you never use?

Answer 10

Never use pilot mic or headphone

Use a known serviceable mic and headphone

Question 11

How would you test the audio integrity in the aircraft?

Answer 11

Load a mic and phone jack with resistors until the measured V is half its unloaded value, this gives you the IMPEDANCE of a circuit

Question 12

Why is there a voltage in the mic audio line?

Answer 12

To give the mic a power to operate

Question 13

Headphone impedance is what?

Answer 13

500-600ohms

Question 14

What are the 3 types of microphones?

Answer 14

Electret
Dynamic
Carbon

Question 15

Which of the microphones require an amplifier and why?

Answer 15

Electret and Dynamic

They only produce mV outputs

Question 16

How does the electret microphone work?

Answer 16

sound = diaphragm vibration = distance btwn diaphragm and plate = electric signals
capacitance change

Question 17

How does the dynamic microphone work?

Answer 17

A diaphragm moves a magnet/coil which creates a current

Electromagnetic effects

Question 18

How does the carbon microphone work?

Answer 18

sound = carbon compressed by diaphragm = resistance change = current flow

Question 19

What are the 3 parts of a jack?

Answer 19

Tip, Ring, Ground/Barrel

Question 20

Which part of the jack is the PTT and what does it do?

Answer 20

The tip

When PTT is activated, tip is grounded which then we go from Rx to Tx

Question 21

Which part of the jack is the audio?

Answer 21

The Ring which has a DCV supplied from radio

Question 22

Which part of the jack is common to the PTT and audio?

Answer 22

The ground

Question 23

Aircraft microphones require a bias voltage of?

Answer 23

9V

Question 24

Microphone impedance is what?

Answer 24

150ohms AC

Question 25

Typical output voltage of microphones are what?

Answer 25

1Vrms

Question 26

Which microphones can you change the output of?

Answer 26

Electret and Dynamic

Question 27

Typical frequency response for headphones is what?

Answer 27

3kHz to 300Hz

Question 28

Headphone has how many ohms in the input and output?

Answer 28

500 in 500 out

Question 29

Speaker has how many ohms in the input and output?

Answer 29

500 in and 3 out

Question 30

Mic has how many ohms in the input and output?

Answer 30

150 in and 500 out

Question 31

What is howling?

Answer 31

When the mic is too close to the speakers

Question 32

On a speaker amp test, how do you set it up and what are the outputs?

Answer 32

1Vrms and 1kHz signal from audio gen | should see 1V in and 1V out

Question 33

For the speaker amp test, when should distortion happen?

Answer 33

between 5-6V

Question 34

On a headphone amp test, how do you set it up and what are the outputs?

Answer 34

1Vrms and 1Khz signal from audio gen | 1V in and 1V out

Question 35

During a headphone amp test, when increasing the voltage to 5 what happens?

Answer 35

No distortion

Question 36

On a mic amp test, how do you set it up and what are the outputs?

Answer 36

0. 5Vrms and 1kHz signal to mic jack | 0. 5V in and 2.5V out (around 5x gain)

Question 37

On a mute function test, how do you set it up and what is the output?

Answer 37

`3Vrms and 1kHz signal | operating ptt = mute

Question 38

What is the bandwidth test?

Answer 38

Set 1kHz as reference then increase/decrease and see where the power goes to 1/2 or 70% (0.7V out)

Question 39

For power conversions what are the decibels?

Answer 39

3dB and 10dB

Question 40

For voltage conversions what are the decibels?

Answer 40

6dB and 20dB

Question 41

What is the reference level for dBm units?

Answer 41

1mW

Question 42

What is the reference level for dBw?

Answer 42

1W