StratuxChoosing and identifying Stratux radios
Almost any RTL-SDR works as the 1090 MHz radio. The 978 MHz radio on current builds is the red UATradio, which is not an SDR and has no PPM or gain settings. Serial numbers on the dongles are optional.
The 1090 MHz radio
Stratux doesn't restrict which RTL-SDR tuner you use. If the dongle has to fit inside the case, buy a "nano" size. A single dongle is all you need to replace a failed one.
| Stick | Notes |
|---|---|
| Blue (filtered) | Works for 1090 MHz only |
| Orange (unfiltered) | Can be tuned to 978 or 915 MHz |
| Metal case | Tolerates heat better |
| Nooelec Nano 3 | Anecdotally no better than the Nano 2+, and one report of more interference with GPS. Other users like its slimmer shape. Treat this as anecdote. |
The Stratux low-power SDR is a generic SDR with switching regulators. It is noisier, but that doesn't matter at 1090 MHz.
You need a 1090 receiver even in the US. UAT traffic is sparse and short range, and most general aviation aircraft end up with 1090 out. If you only want 1090, leave out the 978 radio or untick 978 Mhz (UAT) in the settings.
The 978 MHz UATradio
The red Stratux UATradio is a dedicated 978 MHz receiver built on a TI CC1310 chip. It connects to the 978 antenna port through a small u.FL pigtail. It decodes on the chip and sends frames to the Pi over serial.
- It has no PPM, gain or tuner settings. Those apply only to RTL-SDR dongles.
- It uses roughly one tenth of the power of an SDR and saves Pi CPU.
- A 1090 SDR can't receive 978 MHz, whatever you do with the antenna.
- Much older documentation still calls it an SDR. On current builds, it isn't one.
The usual setup is one SDR for 1090 plus one UATradio for 978. If the 978 side stops working, check the UAT count on the status page and the pigtail. See Stratux antennas.
Telling the radios apart
- By look: the red board is the UATradio. The nano-format SDR is the 1090 radio.
- By test: plug in a stick without a 978 antenna. If traffic appears, it's the 1090 stick. 978 is hard to receive on the ground.
- By serial: read it with
rtl_eepromon a Linux PC.
Serials are optional
Stratux assigns SDRs to bands by their EEPROM serial prefix, such as stratux:1090 or stratux:978. Untagged dongles are assigned automatically to whichever enabled band still needs a radio, so swapped antennas still work. A stx:0 serial gives a single-dongle fallback: 1090 first, then 978 if there is no UAT dongle. The PPM value comes from the serial suffix if there is one, otherwise from the global PPM Correction setting.
Most modern dongles run fine at 0 PPM. If you miss traffic, try small changes of about ±5. The GSM calibration instructions in the settings help are obsolete in North America.
Stratux can only run as many protocols as it has receivers. If you enable more than that, the web UI shows an error saying so. Untick the band you don't have a radio for.
Pong, the combined radio
Pong is a dual-band 1090 + 978 module that decodes both bands on board. It talks to the Pi over a serial device, and Stratux detects it automatically. There is also a Pong ADS-B Receiver switch in the settings. It is made by a community member. Availability is unsettled, so don't count on being able to buy one.
Heat
All of these radios run warm. A failed or overheating 1090 SDR can drop traffic about a minute after boot. It can also make the GPS disconnect, with the web UI showing 0 SDR devices. To find a bad device, plug them in one at a time and watch the 1090 message-rate bar. Dongles are cheap to replace.
For more background, see What's inside a Stratux, and no weather or traffic if you're testing on the ground.
Get help
Ask in the Discord.