Bouncing VHF/UHF Signals Off Aircarft

Keen VHF DXers are always looking for an edge when it comes to predicting propagation.  While it's been known for many years that aircraft can enhance VHF/UHF signal paths, predicting the effect in real-time is more difficult.  Thanks to Frank DL2ALF, we have the answer in the form of Airscout.

Airscout has many cool features such as incorporating Digital Terrain Elevation Data (DTED) which takes account of terrain when calculating if a station is Line of Sight to each aircraft, different reflection models for each amateur bands and a network connection with another great program from Frank, wtKST, an ON4KST chat client which shows live aircraft scatter to all the users logged into KST.

The picture below shows the single path between our contest site for G3M and the Frank DL2ALF on 1.2GHz.  The grey aircraft will have no effect on the signal, the orange aircraft might if they change path or altitude just a little, the red aircraft will become helpful if they remain on course and at the same altitude, and the pink aircraft are in the right place to help right now.

Of course, to get the live plane data, an internet connection is needed.  Frank has coded multiple different connections to internet plane feeds but these rely on third-party sites allowing access to their data.  Increasingly these sites are looking to monitise their systems and are either limiting the number of free look-ups or refusing connection without a paid account.  While annoying, up until recently it's been possible to get a working system by selecting several different sources of aircraft data in the Airscout configuration.  During 2022 the problem became so acute that Airscout has barely worked for casual VHF/UHF DXers and is practically useless for the heavy use which contest operations demand.

The answer was to create a server collecting aircraft data and sharing the data with registered radio hams.  Thomas OV3T has done just that.  There is a Facebook group where users can register and get help with the server.  Find it here:  ADSB data for Airscatter. 

Of course, the system will only work with a network of ADS-B receivers sending aircraft data back to the server.  Fortunately, the solution is simple and relatively cheap.  All that is needed is a Raspberry Pi 3/4, an RTL SDR dongle, an antenna, and an internet connection.  Configuration takes about an hour and once working, requires no user actions.

I had all the necessary equipment within arms-length of my shack chair so put together a system on the bench using just a 1/4 dipole placed in the window of the shack.  As well as sharing the received data with Thomas and fellow amateurs, it's possible to connect locally to the Pi and see the activity.

The next step is to put a better antenna up above the roofline of the club which should dramatically extend the range and number of aircraft we can see.

There are already a number of receivers around Europe though more are needed in some areas such as EI and F.

Thanks to Frank DL2ALF and to Thomas OV3T for both these excellent systems.  We look forward to testing them thoroughly in the March 2m / 70cm contest.