With my FlightAware feeder now permanently mounted outside, I began thinking of installing a second ADS-B/Mode-S feeder at the opposite side of my apartment. Would the extra reception coverage be worth the costs, as the second antenna could only be placed inside, blocked by some nearby obstacles. Earlier tests with a NooElec NESDR SMArt dongle and a simple antenna had been quite disappointing, but after placing the antenna behind a solid wall instead of a window, reception suddenly became interesting enough to make me buy a second RasPi + FlightAware Pro Stick Plus + 66 cm antenna.
Antenna coverage graphs of both feeders
First I had the second RasPi run just dump1090-fa (not the complete Piaware suite) and forward its decoded messages to the first feeder. A picture on the FlightAware site illustrates how processes are linked together.
[not shown is port 30004, on which dump1090-fa is listening for incoming ADS-B messages from other feeders]
I used netcat for forwarding messages from one feeder to the other:
nc -d localhost 30005 | nc -q1 <ip_of_second_Pi> 30004
Forwarding messages from dump1090-fa to the FlightAware feeder boosted its detected aircraft figure, but (inevitably?) at the cost of its MLAT synchronisation/reception. So I ended up with both feeders running Piaware and showing up as two separate ‘sites’ under my flightware.com account. For visualizing detected traffic from both receivers I use Virtual Radar Server’s local webpage (http://127.0.0.1:88/VirtualRadar/desktop.html#) on a Windows laptop.
The image below shows my Virtual Radar, with combined coverage graphs of both receivers’ ADS-B & MLAT reception. The outer black circle is at 400 km from my location, so I’ve been receiving aircraft from well over 600 km distance. Occasionally, particularly when nearby traffic is low, the receivers pick up positions from even further distances (800+ km), but these are too irregular to be represented in VR’s coverage graph.
[ I could figure out which of the feeders gets most MLAT aircraft, and then forward that feeder’s ADS-B messages to the other feeder. This would stop that other feeder from receiving MLAT aircraft and make it feed FlightAware with ADS-B aircraft from both feeders. That would substantially raise its site ranking as well as my FA user ranking (ADS-B aircraft from the first feeder would be counted twice). I suspect that FA wouldn’t be pleased, so I’ll stick to operating two strictly separated feeders. ]