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ACSO 2403 > COMMS > Flashcards

COMMS Flashcards

1
Q

01 What are the Propagation Paths?

A

Ground Wave
Tropospheric Wave Ducting
Sky Wave

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2
Q

01 What is a ground wave?

A

Portion of radiated energy which is directly affected by the presence of the earth and its surface features

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3
Q

01 What are the components of ground wave

A

Surface wave
Space wave

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4
Q

01 What is a surface wave

A

travels along the surface of the earth and tends to curve over the horizon due to diffraction
Max range in the MF and
low HF bands is ~ 100 NM

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5
Q

01 What is a space wave?

A

made up of the Direct wave and Earth-reflected wave
VHF bands and higher;
range is line-of-sight

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6
Q

01 What is Tropospheric Wave Ducting

A

Part of the radiation that undergoes refraction and reflection in the lower levels of the atmosphere.
Provides extra range to LOS comms
Unpredictable

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7
Q

01 What is a sky wave

A

Waves that travel upward and which are refracted back to earth by the ionosphere.

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8
Q

01 What is a communication system?

A

A system designed for the purpose of transmitting information from one point to another.

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9
Q

01 A basic communication system is made up of three principle parts:

A

The transmitter - generates radio frequency power modulates it with the information to be sent;

The receiver - converts the power into a form from which the information can be extracted, and

An antenna system - radiates and intercepts the radio energy.

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10
Q

01 A radio transmitter is composed of two sections:

A

The radio-frequency section:
generates RF (radio-frequency) waves and
amplifies them so that they have sufficient output power to travel through air or space to the receiver.

The modulator section:
modulates the RF waves with the information that is to be transmitted

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11
Q

01 The radio frequency section of a transmitter consists of:

A

an oscillator: Generates EM
energy at the desired
frequency. This frequency is called
the CARRIER WAVE

amplifiers: Increases the power of the signal to a level sufficient for transmission

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12
Q

01 The Modulator section of a transmitter consists of:

A

INFORMATION (INTELLIGENCE): Used to enter the desired info into the transmitter (microphone, keyboard, computer, etc.)

MODULATOR: Impresses the intelligence onto the carrier wave using many different methods

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13
Q

01 The receiver consists of three basic parts:

A

Selective Circuit: provides selectivity by only allowing energy of a pre‑tuned frequency to pass into the receiver.
This frequency contains both the carrier wave and the intelligence.

Detector: detects and demodulates the intelligence from the carrier wave. (splits the wave in two so we can read the intelligence portion)

Audio Amplifier: (voice radio only) steps up the power and reproduces the intelligence signal for use.

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14
Q

01 What are the receiver characteristics

A

Frequency coverage

Sensitivity

Selectivity

Fidelity

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15
Q

01 What are the Desirable Receiver Functions

A

Intercept some of the RF energy from the transmitter.

Select the correct RF from a multitude of signals.

Detect and separate the intelligence from the carrier wave.

Reproduce the intelligence into some meaningful form.

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16
Q

01 What is receiver frequency coverage?

A

The range of radio frequencies which the receiver can handle.

A single receiver cannot intercept all frequencies.

Receivers are optimized for specific frequency bands.

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17
Q

01 What is receiver sensitivity?

A

Ability of the receiver to intercept weak signals and extract the intelligence.

A highly sensitive receiver will work for both strong and weak signals.

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18
Q

01 What is receiver selectivity?

A

Ability of the receiver to intercept and extract intelligence from a desired signal and exclude all others.

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19
Q

01 What is receiver fidelity?

A

The ability to reproduce the transmitted intelligence.

A high fidelity receiver is not necessarily required for voice comms, but is desirable for such things as a data link.

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20
Q

01 What is the frequency produced by the RF section of a transmitter called?

A

carrier wave

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21
Q

01 What does the antenna system do?

A

Couples the radio to free space by radiating RF energy from the transmitter and capturing RF energy by the receiver.

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22
Q

01 What is modulation?

A

Modulation is the process of varying a carrier signal so that it can convey a message.

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23
Q

02-03 What is a sub-form of AM?

A

SSB modulation

24
Q

02-03 What are three advantages of SSB Modulation?

A

More effective use of avail EM spectrum
Better quality of intercepted signal
Higher % of power used to tx the intelligence

25
Q

02-03 Why does SSB modulation provide a better quality of sound at the receiver?

A

Intercepted signal is of better quality.
Better signal-to-noise ratio compared to full sideband modulation.

26
Q

02-03 What is the main operational disadvantage of FM?

A

Restricted to LOS due to its use of higher frequencies.

27
Q

02-03 What are the three digital forms of modulation?

A

Phase modulation
Pulse modulation
Frequency shift keying

28
Q

02-03 What are the three forms of modulation?

A

Amplitude Modulation (AM)
Frequency Modulation (FM)
Digital Modulation

29
Q

02-03 What is Amplitude modulation (AM)

A

Modulation method where the amplitude of the carrier wave is increased or decreased in accordance with the changes in the audio signal to be conveyed.

Amplitude modulation produces a signal with power concentrated at the carrier frequency and in two adjacent sidebands.

The transmission bandwidth of an AM signal is more than twice that of the baseband signal.

30
Q

02-03 What makes up the sidebands?

A

Sum frequency or upper sideband (USB) = carrier wave frequency + audio frequency
Difference frequency or lower sideband (LSB) = carrier wave frequency – audio frequency

31
Q

02-03 What is Single Sideband (SSB) Modulation

A

Form of AM where only one sideband is used to convey information, the rest of the signal is suppressed at the transmission.

No intelligence is conveyed by the carrier wave itself.

Since USB and LSB are mirror images of one another, it is redundant to send both side bands.

32
Q

02-3 What are the SSB - Advantages

A

Less power is required for transmission.
-No power is used to transmit the LSB or carrier (carrier wave takes up 2/3 of the antenna power).
-Higher percentage of power can therefore be used to transmit the intelligence.

Only half of the bandwidth is occupied.
-This allows a more effective use of the EM spectrum.

Intercepted signal is of better quality.
-SSB modulation has a better signal-to-noise ratio because it is at least half the size and therefore less susceptible to interference (refer to film).
-SSB modulated signal is also less susceptible to selective fading (when an AM signal strikes the ionosphere, the USB hitting it first will be refracted out of phase with the carrier and LSB.
-This causes distortion when the signal is demodulated at the receiver.
-If only one sideband is used, it can’t be out of phase with itself).

33
Q

02-03 What is Frequency Modulation (FM)

A

Modulation method where the frequency of the carrier wave is modified to reflect the changes in the audio signal to be conveyed.
-The loudness or amplitude of the audio signal determines the amount of frequency change to the resting carrier frequency.
-The pitch or frequency of the audio signal determines the rate at which the carrier frequency is affected.

34
Q

02-03 What is the FM VS AM - Advantages

A

FM signal-to-noise ratio is better than AM
-Due to its larger size (because amplitude of the signal is varied to convey the information), an AM signal is more susceptible to noise or interference. (Refer to film.)
-If the noise affecting an AM signal is cut, some of the intelligence may be lost as well.
-With FM, limiting the noise does not affect the frequency of the carrier as much and the information can be rendered more clearly.

FM has better fidelity at reception
-To avoid extremely large system components required by high amplitude signals, AM is generally restricted to a narrower bandwidth.
-Because it does not have the large components problem, FM can use a broader bandwidth which allows for all the highs and lows of the original intelligence.

FM allows transmission of signal at constant peak power (because amplitude of the signal does not change).
-Because the signal modulated by frequency does not vary in amplitude, the transmitter tubes may be operated at peak efficiency at all times.

35
Q

02-03 What is the FM VS AM - Disadvantages

A

More complex equipment is needed

More bandwidth is used.
-As with AM, sidebands appear above and below the carrier, but the relationship is much more complex and beyond the scope of today’s class.
-Suffice to say that the bandwidth of a commercial FM station is 200 KHz or 20 times that of an AM station.

The main operational disadvantage of FM is that it is restricted to line-of-sight, due to its use of higher frequencies (29.999 MHz and above).
-On VHF and UHF radios, AM is still restricted LOS but HF radios i.e. lower than 30 Mhz provide Beyond Line-of-Sight (BLOS) capability.

36
Q

02-03 What are the Digital Modulation - Advantages

A

Send more types of data
Text
Pictures/video
Tactical information

Encryption

Higher fidelity

Better signal to noise ratio

37
Q

02-03 What are the Digital Modulation - Disadvantages

A

More complex equipment
More complex transmission protocols
Require Error Correction Codes

38
Q

02-03 What is phase modulation?

A

A form of modulation where the phase of the carrier wave is varied by the intelligence signal.

Normally used to transmit digital signals.

39
Q

02-03 What is pulse modulation?

A

A form of modulation where the carrier wave is not a continuous alternating wave, but a train of discrete pulses.

Advancements in PM allows for transmission of digital data

40
Q

02-03 What is Frequency Shift Keying

A

A form of modulation where a carrier signal of constant amplitude is frequency modulated to correspond to 0 and 1.

41
Q

02-03 What remains constant during frequency modulation?

A

Amplitude

42
Q

02-03 SSB modulation is a sub-form of what kind of modulation?

A

AM

43
Q

02-03 Which has the better sound quality, FM or AM?

A

FM

44
Q

02-03 What is the main operational disadvantage of FM compared to AM?

A

Restricted to line of sight

45
Q

02-03 What does the audio control panel provide aircrew with the means to do?

A

Communicate internally
Transmit externally
Monitor navigation receivers
Access PA

46
Q

04 steps to Identifying Objects Outside the Aircraft

A

Description
Direction (clock system)
High or low indication
Distance
Conflict resolution (“no-conflict” or conflict with instructions)

47
Q

04 what is the High / Low and Distance

A

Always indicate if the object is high or low relative to the aircraft unless it is obvious such as a road or runway.

Give an approximate distance if possible.

Calibrate eyeball using available resources.

48
Q

04 What is the SLIC rule

A

STOP - If you are talking on ICS, stop!

LISTEN - Listen to the traffic

IDENTIFY - Identify whether or not the traffic is for you directly or relates to your mission.

CONTINUE (or COMMUNICATE and CONTINUE) - Once you are sure that the traffic presents no conflict, you are free to continue.

49
Q

04 What are the options for Non-Intercom Communications

A

Runners
Hand signals or gestures
Eye contact
Written notes

50
Q

05-06 In Winnipeg, and at other large airports, who issues VFR or IFR clearances?

A

Clearance delivery.

51
Q

05-06 What are the required standard calls to WOPS at 402?

A

Start crew
Taxi advisory
Airborne call
Inbound call
Taxiing in call

52
Q

05-06 When do you call WOPS nd what information do you provide them in air?

A

Appox. 20 mins back from airport:
Lead will contact WOps and provide the ETA to the ramp, expected fuel on landing, SOB, and the aircraft serviceability.

53
Q

05- 06 Who do you call for the following clearances?
Flight Plan Clearance
Taxi Clearance
Arrival Clearance
Take-off / Landing Clearance

A

Flight Plan Clearance (Clearance Delivery)
Taxi Clearance (Ground Control)
Arrival Clearance (Arrival Control)
Take-off / Landing Clearance (Control Tower)

54
Q

05-06 What is a blind broadcast?

A

A Blind Broadcast is a VHF call by an aircraft stating its position and intentions to inform other air traffic that may be in the area. They can be either:
Directed (ie. to a specific aircraft or aerodrome).
Non-Directed (broadcast out when in a general area).

55
Q

When flying VFR in uncontrolled airspace or on an airway, which frequency should be monitored continuously and blind broadcasts sent frequently as a general update of your position?

A

126.7

56
Q

05-06 Per the ACSO GB, who will you contct to obtain the latest Metar and TAF?

A

contact the nearest FIC

ACSO 2403 (5 decks)

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