Decoding ADS-B

ADS-B - Decoding and displaying aircraft tracking data

I've been interested, for a long time, in watching the various websites showing aircraft data in real time, but not got around to doing it directly with an SDR - Software Defined Radio receiver - relevant applications and a suitable antenna.

After investigating what programmes were available for the Windows environment, I chose: RTL1090 and Virtual Radar Server.

RTL1090

RTL1090 is a non tunable 1090 MHz receiver application for Mode-A/C or Mode-S transmissions.

Mode A equipment transmits an identifying code only.
Mode C equipment enables the air traffic controller see the aircraft altitude or flight level automatically.
Mode S equipment has altitude capability and also permits data exchange.

ADS-B (Automatic Dependent Surveillance Broadcast) is a technique that relies on aircraft or airport vehicles broadcasting their identity, position and other information derived from on board systems (GNSS etc.)

This signal can be captured for surveillance purposes on the ground (ADS-B Out) or on board other aircraft in order to facilitate airborne traffic situational awareness, spacing, separation and self-separation (ADS-B In).

Virtual Radar Server

Virtual Radar Server is an open-source .NET application that runs a local web server.

You can connect to the web server with any up to date browser and see the aircraft plotted on a map.

After configurations, these applications receive the local ADB-S 'S' mode transmissions and show aircraft details as a map overlay. The end effect is virtually identical to the web based and mobile 'phone based views, except for not needing an Internet connection and only being able to see a limited number of aircraft dependent on the antenna gain and location.

With an internal HB9CV - cut for 70 cm ! - I was still able to see plots up to around 40 miles distance: