RJ Fundamentals Flashcards
What is TMR, what manufacturers are there and what frequency is it
Trunked mobile radio - Off the shelf emergency and military handheld radio
Tetra, MPT 1327
380 - 410 mhz
What is DMR,
What manufacturers are there and what frequency is it
Digital Mobile Radio
Used for longer distance, high volume traffic comms
Selex
Hytera
Motorola
66 - 860mhz
What are the qualities of mobile phones?
Cellular Network Architecture
800 - 900mhz older frequencies
2100 - 2600mhz newer frequencies
What is INMARSAT?
British owned, 14 geostationary satellite service to provide position when in beam of a satellitle.
Government Aid Agencies, Media and businesses
Downlink - 1525 - 1559mhz
Uplink - 1626 - 1660mhz
What is DAB and what frequencies?
Digital Audio Broacast
194 - 229mhz
What is DVB and what frequencies and what is significant?
Digital Video Broadcast
470 - 850mhz UAV can hide in frequencies
What are the qualities of pagers?
1 Way or 2 way, fixed transmitters short range with numeric or voice data
What are the frequencies of WIFI and WIMAX
Wifi - 2.4ghz, 5ghz & US 3.6ghz
WIMAX - 2.3ghz. 2.5ghz & 3.5ghz
What is GPS, how many satellites are required and name the frequencies
Global Positioning System
4 satellites required
Liable to jamming
L1 1575.42
L2 1227.60
L5 1176.45
Name the 2 types of modulation
Angle modulation (Frequency)
Amplitude modulation
Name the 2 types of amplitude modulation
ASK - Amplitude shift Keying
OOK - On Off Keying
Explain Amplitude shift keying
Constant power that is just being altered remaining at the same frequency.
Application: Timing signals
What are the advantages and disadvantages of ASK
Digital signal, simple to implement, transfer and receive
Poor performance under weak signals
Explain On Off Keying
A signal that is turned on and off like morse code. Binary 1’s & 0’s
What are the advantages and disadvantages of OOK
Simple and cheap to tx & rx
Cannot respond to variations in AMP
Vulnerable to atmospherics
Can contain bursts of noise
What is heterodyning
Imposing a frequency on a carrier frequency
Name the 3 types of sidebands
Double or mirror sideband - Duplicated message either side of the carrier - less range, more clarity
Single sideband - 1 message 1 side of the carrier which can be transmitted further - prone to distortion
Independent sideband - 2 independent messages either side of the carrier. 2 messages with same amout of power and requires less bandwidth
What is double sideband used for and its adv disadv
Voice
Cheap simple and easy to maintain
Interference and noise
Lots of power
What is single sideband used for and Adv Disadv
Longer distance telephony & older military comms
Greater distance for same power
Half BW
Complex equip
Distortion
What is independent sideband used for and adv disadv
Telephone and telegraph systems, mil comms and multiplexing
Double info for same amount of power
Complex to tx and rx
What are the types of Angle modulation
Frequency and phase
Name all the position of the AC and their numbers
Rich Techies Always Ask Dead Animals About My Long Socks Award
Ravens 21 22
Tac Co ord 23
ASE 1 17
ASE 3 14
Data link op 5
Airborne Analyst 2
Airborne mission supervisor 1
MSO 3
Linguists, 4, 6-11
SSD 12, 15, 16
ASE 5 18
What is changed on Frequency modulation?
The angular rate
What is changed on phase modulation?
The angular distance
Which frequency modulation is analogue?
Frequency modulated carriers (FM Radio)
Which frequency modulation is digital?
Frequency Shift Keying (FSK)
On FSK carriers, what happens?
Rapid shift between two determined frequencies known as the Space and Mark
What is the excursion?
From Fmax to Fmin
What is the deviation?
From centre freq to Fmax or Fmin
What is frequency shift?
The distance between one peak to the next
What is MLFSK?
Multi level frequency shift keying
What is Modulation rate and what is it measured in?
The number of symbol changes per second measured in bauds or BPS
What is the Modulation Index?
Relationship between the frequency excursion and the modulation rate
How is the modulation index calculated?
Frequency excursion / Modulation rate
E.g 1000hz / 100bps = 10 MI
What is MSK? And what figures are associated with it?
Minimum shift keying
0.5 is the minimum otherwise signal cannot separate enough
23db separate the top of the primary lobe to the top of the secondary lobe
What is the BW of a MSK signal?
MR * 1.5 = BW
E.g 1000 * 1.5 = 1500hz
Explain phase modulation
Where the angle of the wave is caused to change throughout the modulating wave. Amplitude remains the same.
What are the 2 types of phase modulation?
Phase shift keyed carriers
Phase modulated carriers
What Db is associated with PSK?
14db from primary lobe to secondary lobe
What is the calculation for BW on a PSK?
MR x 2 = BW
E.g 1000 x 2 = 2000hz
Describe PSK
Modulation of digital wave forms where the phase of the carrier is varied between constellation points.
Phase angles are measured in degrees and each point represents a 1’s and 0’s
What is Data Rate? How is it calculated?
The amount of info passed on per second.
MR x Bit per permutation
What are the four types of PSK?
BPSK - Binary
QPSK - Quadrature
8PSK - 8
QAM - Quadrature amplitude modulation
Explain BPSK
Bi phase modulation usually between 0 & 180 degrees
One channel of information
1’s & 0’s
MR & DR are the same
Explain QPSK
4 Different states 90 degrees apart.
2 channels of information meaning faster data rate 2 x BPSK
2 bits are represented per state doubling the date rate
Explain 8PSK
8 Different states, amplitude remaining the same
3 bits per state
3 x the date rate
Explain QAM
16 different states, varying amplitude to prevent clutter of phases
QAM can start at 8 and the highest is 256
Doubling the phase state adds 1 bit. E.g 8 = 3, 16 = 4, 32 = 5 all the way to 256.
What is multiplexing?
Sending more than 1 message through the same signal
In basic terms how does multiplexing work?
It is stitched together at the transfer side by a multiplexer, and unstitched at the other end by a de-multiplexer
What are the 2 types of multiplexing?
FDM - Frequency division multiplexing
TDM - Time division multiplexing
How does FDM work?
A carrier signal is sent with messages allocated a unique start stop point 4khz wide (size of a voice grade channel) side by side to each other.
Originally the messages all have the same frequency but are then allocated a frequency and stiched next to each other and the unstitched at the other end.
Do all channels need to be used when transmitting FDM?
No, they will all be sent but not all have information in them
FDM terminology. What are the common types of groups?
12 + 6 channel are most common
Group = 12 VGCs
Super Group = 60 VGCs
Master Group = 300 VGCs
Super Master Group = 900 VGCs
What are the applications of an FDM?
Telephone, Sat comms, Military Comms, Telemetry
What are the adv and disdvant of FDM?
Adv - Send lots of data simultaneously
Disadv - Larger channels = larger BW
What is the centre frequency for a 6 channel FDM?
18khz for even distribution
How does TDM work?
Synchronized switches to separate each signal on the same line through a fraction of time.
All messages will be sent through a sampler and allocated an order sequence e.g 1-6. They will then be sent in that order a fraction at a time and then stitched back together at the receiving end.
What are the applications of TDM?
Telephony
Computers
Satcoms
Telemetry
Tac mil comms
Data comms e.g Data link
Adv and disadv of TDM?
Adv - very BW efficient
Disadv - Complex equipment at both ends
What are the 2 other types of Multiplexing?
Orthogonal frequency division multiplexing - signals overlap but have unique characteristics to separate them and avoid distortion
Code division multiple access - Each signal is provided with a coding scheme
What does Modem stand for?
Modulate, demodulate
What is the purpose of a modem?
To convert a digital signal to and analogue signal and then back to a digital signal using the public switch telephone network
How much BW does a modem take up?
No more than 4khz as it was optimised for VGC
What characteristics can you recognise on a modem?
MR
DR
Modulation type
Centre frequency
What are the common types of proforma?
ATC - Air traffic control
ASV - Air surveillance
SAM - Surface air missile
AIS - Automatic identification system
GCI - Ground control intercept
What is TCAS proforma and what are the frequencies?
TCAS
Independent to ATC and is mandated on AC over 5700kg.
1030 + 1090mhz
What is ACARS, what is it’s code name and what frequency?
ACARS - Aircraft comms addressing and reporting system
Digital data link between AC and GCS via radio or Sat
DIGLASSO
131.55mhz
What is VHF Data Link, the 4 modes and their uses?
Mode 1 = Validation
Mode 2 = Main version (Just data)
Mode 3 = Data and digital voice comms
Mode 4 = Exchange data with ground and other AC
What is mode 2 frequency and code name?
HEELBLUE MODE 2
136.975mhz
What is Mode S, its codename and frequency?
Secondary surveillance comms system supporting ATC. AC has unique address code with transponder.
CINGLE
1090mhz
What is AIS, it’s codename and frequency
Automatic identification system for surface vessel for CAS and exchanging identifying data with satellites, nearby vessels and base stations.
JEEEPNEY
161.975
162.025
What occurs during an emergency procedure crew co-ord?
Warning
Instruction
Ackowledgement
How many emergency exits are there and where?
7 exits
1+2 Cockpit
3+4 Crew entry chute & cargo door
5+6 Emergency hatches over wing
7 Rear Emergency hatche
How many emergency ropes are there?
4; 1 pilot, 1 co pilot, 1 crew chute and 1 rear hatch
What alarms sound during a ground emergency?
3 short rings - prepare
1 Long ring - Abandon
What alarms sound during a ditch / crash landing?
6 short rings - prepare
1 long ring - brace for impact
What alarms sound during ditch / crash immediately after take off?
1 long ring
What happens before ditching?
Prepare - Electrical equipment off
Anti exposure suits + LPUs
Loose gear jettisoned
Secure harnesses and safety belts
What happens once ditched?
Primary exit - Overwing hatches
Secondary - Pilot/co pilot
Not the rear as can cause flooding
How many MS10 life rafts are there?
4 left overwing hatch
What happens before crash landing
Prep - Elec equip off
Loose gear jettisoned
Secure harnesses and safety belts
What happens post crash?
Exit where safest available
Assembly point 11 0 clock from AC
What happens during a landing gear failure?
Crew alert
Pilot actions
Manually lower gear
Crash landing prep
What do you do if you notice smoke and fumes?
Notify
Oxygen
Source and cause
Pilot action
What happens during a fuselage/electrical fire?
Notify pilot and crew
100% oxygen
Locate fire
Combat fire
Crew co-ord
What happens during rapid decompression?
If occurs pilot will
Direct crew 100% oxygen
Initiate descent
ACE’s ascertain cause
Mission continuance
Who is responsible for the CRA? and what do they need to do?
Crew rest area commander - seat 16 SSD
PAX are CRAC responsibility.
Must brief all PAX
Check rear emerg light fitted
CRA oxygen bottles correct level and fitted & in correct bag
LPU - correct number for PAX
Escape rope is there and serviceable
Loose articles
Strapped in and report to TC
Rear cargo net and drawers shut
What is the CRAC to check and report during AAR?
Pre AAR - Strapped in
Post AAR - No fumes
Emergency - Check toilet
What is FFT?
Fast Fourier Transform.
System automatically does it for you and is the change from time domain to frequency domain.
What is the range of the VGC?
300hz - 3400hz
Name the frequency bands
VLF 3-30khz
LF 30-300khz
MF 300-3000khz
HF 3-30mhz
VHF 30-300mhz
UHF 300-3000mhz
SHF 3-30ghz
EHF 30-300ghz
What are the characteristics of a V23 Modem
FSK
1200 Baud rate
Centre frequency 1700hz
What are the characteristics of a V26 A + B Modem
A = QPSK B=OQPSK
1200 Baud rate
Centre Frequency 1800hz
