Comms and EW old Flashcards
What are the three primary qualities of wave energy?
Wavelength
Amplitude
Frequency
What is Wavelength?
The distance over which the wave’s shape repeats.
What is Amplitude?
The vertical size of the wave, measured from the mean level.
What is Frequency?
The number of occurrences of a repeating event, measured in cycles per seconds, or Hertz (Hz).
How is wavelength affected by frequency?
Increased frequency = shorter wavelength
What is the difference between Primary and Secondary radar?
Primary
Operates independently of the aircraft, it depends on receiving a radar echo reflected passively by a target.
Secondary
A transmitted radar signal is used to trigger a response from equipment in the subject.
IFF - Military
SSR (Secondary Surveillance Radar) - Civvie
What are the key principles of IFF/SSR?
IFF and SSR are normally operated in conjunction with a primary radar.
A coded interrogation signal is transmitted to the aircraft and transponders in friendly aircraft receive and decode the signal.
A coded reply signal is sent back. The reply signal is decoded and shown on the radar display along with the primary radar response.
What frequency is the interrogator frequency for IFF/SRR?
1030 MHz
What frequency is the reply frequency for IFF/SSR?
1090 MHz
What is the duration of the pulses for the Interrogator signal on IFF/SSR?
The interrogation frequency is transmitted at 1030 MHz.
It consists of a pair of pulses, each pulse lasting a duration of 0.85μs.
The separation of the pulses determines the mode.
What is Mode S?
Mode S is a discrete selective interrogation, rather than a general broadcast, that facilitates TCAS for civilian aircraft.
Mode S transponders ignore interrogations not addressed with their unique identity code, reducing channel congestion. At a typical SSR radar installation, ATCRBS, IFF, and mode S interrogations will all be transmitted in an interlaced fashion.
What is ACAS and what does it provide?
Airborne Collision Avoidance System (ACAS)
Collision avoidance protection, situational awareness and enhanced safety.
It is a ‘last resort’ collision avoidance system.
What is TCAS?
Traffic Alert and Collision Avoidance System (TCAS)
Utilizes SSR technology and utilizes the transmissions made by aircraft on IFF frequencies. Warns pilots of the presence of other transponder-equipped aircraft, which may present a threat of a mid-air collision.
What is Mode 4 operating mode?
Mode 4 is a secret, military only transponder setting valid for 24 hours. It serves as a military only identification and can be turned on/off.
What is the emergency Transponder Code?
7700
(7-7 off to heaven)
What is the transponder code for a loss of 2-way comms?
7600
(7-6 in a fix)
What is the transponder code for hijack/terrorism?
7500
(7-5 taken alive)
What types of SSR inaccuracies are there?
Fruiting
Garbling
Sidelobe signals
Transponder suppression
What is fruiting?
Fruiting
When the interrogating station receives replies from transponders replying to other ground stations. This results in false SSR responses being displayed.
What military mode of IFF cannot be set in the cockpit?
Mode 2
What is Garbling?
Garbling
If a second aircraft is sufficiently close to the first to be interrogated, garbling may occur. Its reply may overlap that of the first aircraft and the resulting pulses will mix together and be impossible to decode accurately.
What are sidelobe signals?
Sidelobe signals
Sidelobe signals may occur if the transponder is triggered by the SSR sidelobes as well as by the interrogator beam. This causes spurious replies on the display and, at short ranges can produce large sidelobes on the response, which may create a complete ring around.
What types of Electronic Warfare are there?
Electronic Support Measures
Electronic Attack
Electronic Protection
What is Electronic Attack?
Using Electronic Measures or directed energy to attack personnel, facilities or equipment with the intent of degrading or destroying combat capability.
What is a key requirement for Electronic Protection?
Frequency Agility
Crypto
Modulation changes
Complex PRF
ie. Havequick
What is the Range advantage when referring to the Radar Warning Receiver?
An aircraft that is illuminated by an enemy radar is able to intercept the threat radar transmission before the aircraft itself is detected. It receives the full pulse of the Radar via its RWR, whereas the enemy only receives the reflection.
How can a Radar Warning Receiver identify direction of a radar threat?
An RWR can utilize amplitude or phase comparison techniques.
Why do chaff packages consist of varying length filaments?
Chaff is cut to match the half-wavelength of the victim’s radar frequency. The varying lengths allow response to varying frequencies.
What is the fundamental parameter behind radar stealth techniques?
Radar Cross Section (RCS)
What types of electronic defence measures are there?
ECM - Electronic Counter-Measures
ESM - Electronic Support Measures
EPM - Electronic Protection Measures
What must an IR jammer do to be effective?
An IR jammer must disrupt the modulation pattern produced by the missile seeker head.
What are the principle paths in which a radio wave can travel?
Surface Wave
Sky Wave
Space Wave
What are the three main pieces of equipment for an Electronic Support Measure Kit?
RWR - Radar Warning Receiver
MWS - Missile Warning System
LWR - Laser Warning Receiver
What methods of Electronic Attack/Countermeasures are there?
Chaff
Flares
Decoys
Stealth Measures
How does an RWR identify threats?
Receivers and Antennas
Programme Library cross referenced
Threat identified
What is the time unit reference used for flying?
UTC
What is Distress?
Serious, imminent danger requiring immediate interference.
MAYDAY MAYDAY MAYDAY
What is Urgency?
There is a safety concern for aircraft, other vehicle or person on board but does not require immediate assistance.
PAN PAN PAN
What information is required for a MAYDAY call?
Type + PoB
Nature
Intentions
Position
Level
Heading
TNIPLE
Surface wave propagation is suitable for what uses?
Submarine Communication
Systems requiring consistency of signal over long distances
What frequency bands are suitable for surface wave propagation?
VLF
LF
MF (to some extent)
Describe the principles behind skywave propagation?
Sky waves ascend into the upper atmosphere and encounter the ionosphere.
The electrically charged particles in the ionosphere allow refraction back towards earth
What is the skip distance in sky wave propagation?
The skip distance is the distance between the transmitter and the point of reception of the first sky wave.
What is the maximum usable frequency for sky wave propagation?
MUF is the highest frequency at which reflection can take place for a given angle of incidence.
If the frequency is increased, a sky wave penetrates more deeply into the ionosphere before return.
What are the applications of space wave?
Short-range comms
TV and FM sound broadcasting
Radar
Nav and Approach aids
Satellite Communication
What is attenuation?
Attenuation is the reduction of signal strength, also known as fading. It can be caused by obstructions, absorption, interfering waves and the configuration of the transmitter and receiving antenna.
How can diffraction be utilized to aid signal transmission?
Diffraction can occur as waves deflect around obstacles placed in their path.
The wave spread into the shadow zone behind the obstacle. This can be used to send radio signals over a mountain range where there is no LoS path available.
What is the role of a transducer in a basic radio system?
The transducer creates a baseband signal from an analogue input (comprising a wide spectrum of frequencies)
What is the role of modulation and power amplification in a basic radio system?
It is the role of the transmitting equipment to convert the baseband signal into a suitable part of the frequency spectrum for transmission.
What frequency range is utilized for VHF transmissions?
30-300 MHz
For comms:
118 - 136.975 MHz
8.33 KHz spacing
1300 VHF frequencies
What is the spacing of VHF frequencies?
8.33 kHz
What is the spacing of UHF frequencies?
25 kHz
What is the usable frequency range for UHF transmissions?
25.0 - 399.95 MHz
with 25 kHz
What is a CCS and what services will it typically provide?
Communications Control System (CCS)
These are used in multi-crew aircraft and offer crew members the option to communicate with each other through an intercom.
Intercom and radio facilities for the crew
‘Listen only’ positions
External inputs: ground crew
What is an auxiliary jack box?
Cabin/ground crew can use the normal intercom by plugging a headset into a convenient ‘jack box’.
This action closes a switch, which provides a path from the 28V DC supply to the relays in the crew amplifier.
What is the difference between: clearance, instructions and information?
Clearance: Requires strict compliance.
Instruction: To be followed and carried out where practically possible and safe to do so.
Information: Of benefit and usefulness between Pilot and Ground personnel in the interest of safety.
What time is used for transmissions?
UTC - Coordinated Universal Time
What suffix is used to describe an Area Control service?
CONTROL
What suffix is used to describe a Radar service?
RADAR
What suffix is used to describe an Approach Control service?
APPROACH
What suffix is used to describe an Aerodrome Control service?
TOWER
What suffix is used to describe an Approach Control Radar/Arrival Departure service?
DEPARTURE
ARRIVAL
What suffix is used to describe a Ground Movement Control service?
GROUND
What suffix is used to describe a Military Aerodrome Traffic Zone Crossing?
ZONE
What suffix is used to describe a Precision Approach Radar service?
TALKDOWN
What suffix is used to describe a Flight Information service?
INFORMATION
What suffix is used to describe an Air/Ground Communication Service?
RADIO
What suffix is used to describe a Clearance Delivery service?
DELIVERY
On the readability scale what does 1 indicate?
1 = Unreadable
On the readability scale what does 2 indicate?
2 = Readable now and then
On the readability scale what does 3 indicate?
3 = Readable, but with difficulty
On the readability scale what does 4 indicate?
4 = Readable
On the readability scale what does 5 indicate?
5 = Perfectly readable
What are the emergency radio frequencies?
VHF - 121.500 MHz
UHF - 243.000 MHz
What does code 7500 indicate?
Unlawful interference
What does code 7600 indicate?
Total Radio Failure
What does code 7700 indicate?
Emergency
Describe the order of the EM Spectrum from Radio Waves
Radio
Microwaves
Infrared
Visible Light
Ultra Violet
X Rays
Gamma Rays
What are the three primary qualities of wave energy?
Wavelength
Amplitude
Frequency
What can the propagation of electromagnetic waves be affected by?
Reflection
Attenuation
Refraction
Diffraction
What effect reduces signal strength and limits range of radar signals due to Obstructions, Absorption (water vapor) and Dust particles?
Attenuation
What phenomenon causes waves to appear to bend around objects?
Diffraction
What effect, caused by a change of velocity as an electromagnetic wave passes from one medium to another?
Refraction
Change of medium, velocity changes as medium becomes denser on one side..
Angle in and out do not need to be the same
What effect takes place when the angle of incidence is equal to the angle of reflection?
Reflection
In and out are identical.
Which of the three atmospheric variables cannot affect the refraction of EM waves without changes in the other variables?
Pressure
(Atmospheric variables are moisture, pressure, temperature)
What are the three classifications for refraction?
Sub refraction
Normal refraction
Super refraction
What are the three principal paths that radio waves may follow above the Earth, between a transmitter and a receiver?
Space
Sky
Surface
What effect occurs in abnormal climatic conditions, when some radio waves are refracted back to the surface, then reflected, therefore trapping the wave energy and leading to performance anomalies?
Ducting
What is the frequency range of the VHF band?
30 - 300 MHz
What is the frequency of the HF band?
3 - 30 MHz
What is the frequency of the UHF band?
300 - 3,000 MHz
What do radio waves consist of?
Oscillating electric and magnetic fields which are at right angles, or transverse to the direction of propagation.
Electrical - vertical (fingers in a plug socket, hair stands up)
Magnetic - horizontal
Will radio waves pass through many opaque bodies?
Yes, but will be attenuated in the process.
Which path of radio propagation relies on the Earth to bend the wave to follow the curve of the Earth?
Surface Wave - utilizes diffraction, VLF and LF
What path of radio propagation is referred to as Line of Sight?
Space Wave
Which frequency bands benefit most from surface wave propagation?
VLF, LF
Utilized by Submarines.
Roughly how many VHF frequencies are there and what is the spacing?
8.33 kHz
1300 frequencies
Roughly how many UHF frequencies are available and what is the spacing?
25 kHz
7000 frequencies
What function on the intercom station box can be set to bypass the press to talk switch?
Hot Mic
What part of the CCS is provided at each of the principal crew positions and permits individual selection of transmitters and receivers as required?
Intercom Station Box
At a console or on flight deck, to plug into and select frequencies.
What is the difference between primary and secondary radar?
Primary - operates independently of subject aircraft, passive. Relies on a reflected signal from the target.
Secondary - Active, relies on transponder replying to interrogation.
What frequencies does IFF/SSR use?
1030 MHz Interrogator
1090 MHz Response
Why was Mode S introduced?
Automation of ATC functions.
What military IFF mode and civilian SSR mode are the same?
IFF Mode 3
SSR Mode A
These are the same.
Which military IFF modes can be set on the cockpit control panel?
1, 3
Mode 1 (squawk code, task specific i.e. 42/43 for tanker)
Which military IFF mode is pre-set and therefore not selectable in flight?
2
Airframe specific, precedes Mode S, decoded provided Sqn and tail number
Which mode may you be asked to squawk to assist ATC in locating you on their display?
IDENT
This switches the transponder into permanent transmit for 18 seconds (3 rotations)
What are the three IFF/SSR codes?
7600 - Lost comms
7700 - Emergency
7500 - Hijack
What IFF phenomena occurs when the interrogating station receives replies from transponders replying to other ground stations?
Fruiting
What IFF phenomenon occurs when two aircraft are sufficiently close enough to each other that their resulting reply pulses mix together and cannot be decoded accurately?
Garbling
What term describes the equipment used to pass tactical information between units in a manner that can be understood and absorbed into the units’ systems?
DATA LINK
What prefix precedes a distress call?
MAYDAY, MAYDAY, MAYDAY
What prefix precedes an urgency call?
PAN, PAN, PAN
What is the correct meaning of ‘roger’?
Received all of your last transmission
What are the emergency frequencies?
VHF 121.500
UHF 243.00
What is the usual format for transmitting time?
UTC
What is the purpose of the military broadcast SECURITE, SECURITE, SECURITE?
Temporary danger areas and SAR OPS
Lat/Long, Flight Level, Radius. e.g. Mountain Rescue airborne ops.
Transmissions on radio should be…
Slow and steady
Normal tone
No hesitations
Constant volume
Listen out, and don’t step on people.
What conditions are categorized as urgent?
Safety concern but not immediate
What information could be included in an emergency message that may be useful to the controller?
Pilot’s qualifications
If you lose sight of the marshaller you should…
Stop.
What is the purpose of the ground marshaller?
Safety
Who is ultimately responsible for the safety of the aircraft whilst maneuvering on the ground?
Aircraft Commander
What is the recognized marshalling signal for an engine fire?
Figure 8 and point at fire.
What is the recognized marshalling signal for cutting an engine?
Hand across throat
What is electronic warfare (EW)?
The use of the EM spectrum to attack the enemy.
What are the three types of EW?
ESM - Electronic Support Measures
EA - Electronic Attack
EP - Electronic Protection
What is the name for actions taken to prevent or reduce an enemy’s effective use of EM spectrum, such as jamming?
Electronic Attack
What equipment is designed to detect, localize, and identify threat radars so that appropriate countermeasures can be taken?
RWR
Radar Warning Receiver
An RWR should normally be able to intercept a threat radar before the aircraft itself is detected. The margin of this benefit is known as what?
Range Advantage
To ensure the ECM are effective what must they do?
Transmit waveforms that are accepted by the receiver
Why would a pilot consider canceling afterburners and reducing engine power to ‘military range’ during takeoff in hostile conditions?
Reduce IR profile
What name is given to the deliberate radiation or re-radiation of EM energy to impair the effectiveness of electronic devices, equipment, and systems?
Deception
Jamming
Which EW systems are classed as Electronic Support Measures (ESM)?
RWR
MWS
LWR - Laser Warning
What is designed and programmed to identify threats, give warning to the crew, and, where available, generate countermeasures?
DAS
Defensive Aids Suite
What does an aircraft’s IR jammer try to disrupt?
Modulation of the incoming IR energy
Give as many examples as possible of measures that provide Electronic Protection?
Planning
Training
Design
HAVEQUICK
Crypto
Parallel Ops
What does the acronym RCS stand for?
Radar Cross Section
What are the main factors affecting an aircraft’s RCS?
Size
Shape
Material
