G1AFI presents

1
G1AFI presents

• SBS-1 Virtual Aircraft Radar Display

2
The SBS -1

• Receives, decodes and displays data transmitted
  by aircraft on 1090 MHz
• Two types of data mode are used
• MODE-S which does not show position data
• ADS-B which can but may not show position data

3
Getting Technical

• Traditional Secondary Surveillance Radar (SSR)
  stations interrogate all aircraft within their
  range,
• Mode S (Select) establishes selective and
  addressed interrogations with aircraft within its
  coverage. This improves the quality and integrity
  of the detection, identification and altitude
  reporting.

4
ADS-B - Automatic Dependent Surveillance

• Broadcast (ADS-B) standards are currently being
  developed jointly by the FAA and industry. The
  concept is simple
• Aircraft (or other vehicles or obstacles) will
  broadcast a message on a regular basis, which
  includes their position (such as latitude,
  longitude and altitude), velocity, and possibly
  other information.
• Other aircraft or systems can receive this
  information for use in a wide variety of
  applications. Current surveillance systems must
  measure vehicle position, while ADS-B based
  systems will simply receive accurate position
  reports broadcast by the vehicles.

5
Example

• As a simplified example, consider an air-traffic
  control secondary radar.
• The radar measures the range and bearing of an
  aircraft.
• The bearing is measured by the position of the
  rotating radar antenna when it receives a reply
  to its interrogation from the aircraft, and the
  range by the time it takes for the radar to
  receive the reply.
• The beam of the antenna gets wider as the
  aircraft get farther from the antenna, thus
  making the measured position information less
  accurate.

6
ADS-B

• An ADS-B based system, on the other hand, would
  listen for position reports broadcast by the
  aircraft. These position reports are based on
  accurate navigation systems, such as satellite
  navigation systems (e.g. GPS).
• The accuracy of the system is now determined by
  the accuracy of the navigation system, not
  measurement errors.
• The accuracy is unaffected by the range to the
  aircraft. With the radar, detecting aircraft
  velocity changes requires tracking the received
  data. Changes can only be detected over a period
  of several position updates. With ADS-B, velocity
  changes are broadcast almost instantaneously as
  part of the State Vector report. These
  improvements in surveillance accuracy can be used
  to support a wide variety of applications and
  increase airport and airspace capacity whilst
  also improving safety.

7
The Set-up

• As you can see the set up consists of
• an antenna,
• the SBS-1 box and
• a PC, laptop or desktop.
• The supplied antenna is the one with the biscuit
  tin ground plane. I have experimented with a
  couple of antenna designs. One design is a scaled
  version of the well known Slim Jim and

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Prototype from FRARS

• the other is a design I modified from one used
  for 2.45 Ghz operation, which claims to have
  between 7 9 dBi gain ?
• I have no means to determine whether this could
  be true or not!

9
Cont

• The slim Jim sits beside a 2m/70cm colinear above
  the roof level and the other one is in the loft
  as it isn't very mechanically stable in its
  present state. No relevant comparison is possible.

10
The Display

• The visual PC Laptop display consists of two main
  components
• A Radar display
• This can have its coverage zoomed as shown on the
  following slides
• A Table containing selectable data available from
  the aircraft.
• There are lots of data available for display but
  I usually have
• Show Trails, Code (Hex code), Reg(istration),Count
  ry, Altitude, Latitude, Longitude, Speed, Track,
  Vertical Rate, Squawk, Last Update and Time
  Tracked in my table.
• For easier readability it might be useful to
  remove some of my table components. This is easy
  to do.

11
The Display Zoomed Out
12
The Display Zoomed In
13
Technical Terms

• There are a couple of terms in the table listing
  with which you may not be familiar, namely Hex
  code and Squawk.
• Hex code is the means by which (all) aircraft are
  identified, each aircraft has a unique Hex Code.
  ( In practice there are always some inaccurate
  Hex codes transmitted, so absolute accuracy of
  reporting, by this method, can not be guaranteed
  ).
• Squawk is a code transmitted by a radar station
  which interrogates a box in an aircraft, which
  enables the radar station to identify the
  aircraft. Squawk codes are issued in a specific
  range for a particular radar station. They
  consist of four octal numbers.

14
Terrain Sections

• When first used the coverage seemed variable
• Good in some directions
• Poor in others
• Used G4JNT software to plot terrain maps
• These help explain the results
• Not the large peaks between
• Poyton (Home QTH) and
• Ottringham
• East Midlands
• Which probably accounts for the poor range from
  these directions.

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Terrain Section

• To East Midlands (EMA)

16
Terrain Section

• To Glasgow International (GLA)

17
Terrain Section

• To Ottringham (East Coast)

18
Terrain Section

• To Wallasey (West Coast)

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Links

• http//www.ringwayreports.co.uk/ringway.htmhttp/
  /www.kineticavionics.co.ukhttp//www.kineticavion
  ics.co.uk/glossary.phphttp//airframes.orghttp/
  /www.gatwickaviationsociety.org.uk/modeslookup.asp