Due to some current events I am interest ... / 2014-03-23

Due to some current events I am interested again in receiving ADS-B signals from aircrafts, I started with ADS-B on the rtl-sdr stick in August 2013. I still have dump1090 working, and I built a colineair antenna based on the design mentioned on SBS-1 & SBS-3 Mode-S / ADSB Virtual Radar : User Forum xx • View topic - How tu build antenna for sbs-1?. Old electric wire was easy to adopt for this target. The result is clearly visible, I can now see high-altitude aircrafts from beyond Eindhoven and Den Helder.

But I also noticed the most 'interesting' aircrafts are the ones that do not show location information in the dump1090 console display. Some are gliders, such as

Hex    Flight   Altitude  Speed   Lat       Lon       Track  Messages Seen   .
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4849c6 PH1280   2025      0       0.000     0.000     0     73        0 sec

But others will send high numbers of messages and when I search on the Hex ModeS code I find them listed as militairy aircraft.

Hex    Flight   Altitude  Speed   Lat       Lon       Track  Messages Seen   .
--------------------------------------------------------------------------------
ae0403 DUKE37   15000     0       0.000     0.000     0     1840      0 sec

Update: It's remarkable that 'lower Dutch airspace' closes at 23:00 localtime. After that time I see nothing below flightlevel 30000 feet (my guess). Looking at Flightradar for Schiphol shows maintenance vehicles and a few late arrivals.

Update 2014-03-24: Ok, one more extra interesting signal:

Hex    Flight   Altitude  Speed   Lat       Lon       Track  Messages Seen  .
--------------------------------------------------------------------------------
4d03cd NATO01   31075     0       0.000     0.000     0     3225      0 sec

One of the Awacs radar airplanes operating from NATO Air Base Geilenkirchen is active, as announced. Lucky you can't hear those very well when they are at 31075 feet. It doesn't announce its location but I think an Awacs radar airplane is perfectly capable of avoiding any plane...

Update 2014-03-25: And the other Awacs plane manages to not get out of range longer than 60 seconds (timeout in dump1090 for tracking a flight), leading to a very high number of messages from one flight:

Hex    Flight   Altitude  Speed   Lat       Lon       Track  Messages Seen   .
--------------------------------------------------------------------------------
4d03c9 NATO02   29000     0       0.000     0.000     0     83597     0 sec