No 1090 traffic, or a radio missing

Short answer: open the Status page and look at the 1090ES message rate and the "SDR devices" count. If 1090ES stays at 0 outdoors, or the count is lower than it should be, a radio has probably stopped working. SDRs are cheap, and replacing one often fixes it.

1. Check the Status page

Connect to the Stratux Wi-Fi and open the web interface at 192.168.10.1 (see Web interface). On the Status page, look at:

  • SDR devices: the number of radios Stratux detects.
  • Messages: a bar for each enabled band (UAT, 1090ES) showing messages in the last minute and the peak.

Check this outdoors with the antennas attached. Indoors, or on the ground with nobody nearby, a low count can be normal. See No weather or traffic. A 1090ES rate that sits at 0 while the unit has clear sky is the real warning sign.

1090 matters even in the US. UAT traffic is sparse and short range, and most GA aircraft are heard on 1090. A UAT-only setup shows little traffic, especially on the ground.

2. Look for the "more protocols" error

Stratux can run only as many protocols as it has receivers. If you enable more than you have radios, the web interface shows a system error: "You have enabled more protocols than you have receivers for." It also tells you how many receivers it found and which protocols it is using.

This usually means a radio dropped out. It can also mean you enabled a band you have no radio for. Either untick the extra protocol on the Settings page, or fix the missing radio. Stratux runs fine as 1090-only if you leave out the 978 radio and untick it.

3. Isolate the bad radio

  1. Power down and unplug every USB device except the one you are testing.
  2. Boot and watch the SDR count and 1090ES bar.
  3. Add devices back one at a time, watching the count and the message rate.
  4. Note which device makes the count drop, GPS disconnect, or traffic stop.

Serial numbers are optional. Stratux assigns untagged radios to whichever enabled band still needs one, so a stick with no serial, or swapped antennas, still works. To tell a 1090 stick from a 978 stick, plug it in without a 978 antenna and see whether traffic appears. Or read its serial with rtl_eeprom on a Linux PC.

4. Rule out heat

A failing or overheating 1090 SDR can drop traffic about a minute after boot. It can also make the GPS disconnect and the SDR count read 0. Check the following:

  • The case has airflow and isn't sitting in direct sun.
  • The Raspberry Pi temperature on the Status page isn't climbing toward its limit.
  • Metal-cased sticks are reported to tolerate heat better.

Also check power. See Power and status lights.

5. Suspect shock damage

If 1090 traffic vanished after a drop or hard landing, suspect the SDRs even if nothing looks broken. In one reported case, replacing both SDRs fixed it, while new antennas and a reflash did not. A fresh image won't fix a damaged radio, but it is still a cheap test. See Update the software.

6. Replace the SDR

Any RTL-SDR works as the 1090 radio. If it must fit the case, buy a "nano" size. Blue filtered sticks only work at 1090 MHz. Orange (unfiltered) sticks can be tuned to 978 or other frequencies. Buy a single dongle to replace a failed one.

If you tweak PPM correction, 0 works for most modern dongles. Try small steps of about ±5 only if you are missing traffic. Don't spend time on the old GSM calibration method.

Software crashes are less of a concern now. dump1090, the 1090 decoder, restarts automatically after a crash.

Still stuck?

Ask on Discord and include a screenshot of your Status page.