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
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.
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.
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.
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.
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
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!
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.
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),Country, 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.
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.
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.