modeac.net

Community flight tracking for the aircraft other trackers miss

modeac.net is a volunteer receiver network. Alongside normal ADS‑B and MLAT, it locates aircraft that don't broadcast their position, like military jets, by timing their transponder replies.

Open the map Start feeding
  • –aircraft
  • –feeders
  • –MLAT receivers in sync

Your feed

Checking for a feed from your internet address…

Feed information

Hostfeed.modeac.net
ADS‑B (Beast)port 30004, protocol beast_reduce_plus_out
MLAT and Mode A/Cport 31090, with the modeac.net client
Who can feedReceivers in the United States

Already running ultrafeeder?

It's three small edits to your docker-compose.yml, about five minutes, and your other feeds keep running exactly as before:

  1. Add READSB_MODEAC=true to ultrafeeder's environment:
  2. Add ;adsb,feed.modeac.net,30004,beast_reduce_plus_out to the end of ULTRAFEEDER_CONFIG
  3. Paste the mlat-modeac block next to ultrafeeder, then docker compose up -d
Full setup guide

Starting from scratch?

A Raspberry Pi, a 1090 MHz USB dongle and an antenna, roughly $120–150 in all, can feed modeac.net and every other tracker at once. Set it up with the SDR-Enthusiasts ultrafeeder guide, then follow the three steps above. On adsb.im or something else? Get in touch and I'll help.

How it works

  1. Radar asks. Air traffic control radar interrogates every transponder in range on 1030 MHz, military jets included.
  2. The aircraft answers. It replies on 1090 MHz with its squawk code and altitude (Modes 3/A and C). There's no position in the reply and nothing is encrypted. Most receivers hear these replies and throw them away.
  3. Receivers time it. When four or more receivers hear the same reply, the tiny differences in arrival time pin down where it came from: the same multilateration ADS‑B Exchange and others use for Mode S aircraft. Then it appears on the map.

Questions

Isn't military IFF encrypted?
Modes 4 and 5 are, and modeac.net doesn't touch them. It only uses the plain replies aircraft send to civilian air traffic control radar, roughly what a controller's scope already shows.
Should I stop feeding ADS‑B Exchange or adsb.lol?
No, keep feeding them. modeac.net runs alongside them and adds what they can't do: aircraft answering only in Mode 3/A and C carry no address, so their MLAT can't place them.
Will my location be public?
No. Your receiver's exact position is only used for the timing maths. Receiver names and locations are never shown on the map or anywhere else on this site.