Build example 3: Include transmission capabilities, so others can see you as well
This build is similar to the pre-built units/kits that are available in Europe, with potentially some slightly different hardware choices in the details. However, instead of the U-Blox GPS, it uses a TTGO T-Beam, which has a GPS on board and also provides transmission capabilities
- Receive ADS-B targets and forward them to the EFB of your choice
- Receive 868Mhz targets (OGN) and forward them to the EFB of your choice
- Transmit on one or multiple 868Mhz based protocols, depending on firmware and configuration
- Optional: provide AHRS, barometric pressure, fan control
- the default OGN-Tracker build transmits OGN-Tracker (868.2/868.4MHz) and PilotAware (868.525MHz) protocols
- OGN-Tracker was chosen as the primary protocol because it transmits at 1sec interval and carries all essential data: timestamp, position, altitude, climb rate, turn rate, can as well carry pressure altitude. It can optionally transmit aircraft registration, pilot name and other data.
- PilotAware transmission makes the Stratux visible to aircrafts equipped with PilotAware, like the Rosette.
- in near future: FANET protocol (LoRa 868.2MHz) could be transmitted as well thus aircraft would become visible to paragliders.
- 868MHz transmission makes the aircraft visible to OGN network: all ground receivers can receive OGN-Tracker, those with updated software can receive PilotAware and FANET as well
- Visibility through TheThingNetwork (LoRaWAN) is operational but requires WITH_LORAWAN compile switch to build and a registration on the TTN, which for now can only be doen through the OGN Team, please contact them if you want to try it: contact@glidernet.org
| Image | Item/Amount | Notes/Source |
|---|---|---|
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1xRaspberry PI | Base board that runs the software. You can either use the model 3B, 3B+ or 4B. All offer the same functionality for Stratux, but 3B draws a bit less power. You might also want to get a heatsink for the CPU as shown in the photo, but this is optional. |
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1xTTGO T-Beam |
IMPORTANT: There are many variants available. You need one that uses 868MHz. It is highly recommended to go for the newer ones with an UBlox M8N GPS module, not the old Ublox 6 ones, as they perform much better. The newer version also features a flexible antenna cable, instead of a fixed, soldered-on SMA connector, which allows for more flexible mounting options. Note that while the T-Beam comes with a small 868MHz antenna, it is not recommended to use that one, since it would be mounted horizontally in the case, which is not optimal. |
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1xCase | There is a variety of ready to use cases available on amazon. We've decided to use our own 3D printed case, as it is nice and compact and has space to fit the T-Beam, which most cases don't. You can get the 3D printable CAD files here https://github.com/b3nn0/stratux/tree/master/notes/case_eu. If you don't have access to a 3D printer and don't know anyone who has, you should be able to use a commercial 3D printing service. Printing this should cost you around 15-25€. Recommended print settings: PETG, bright color to reduce heat from sunlight, 0.2mm resolution. There are STL files provided for different variants. You can either print the case and the 40mm fan lid seperately, or use the combined model to print both at once. |
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1xFan with mounting screws | Any 5v fan should do. Most commercial cases will require a 30x30mm fan. Our 3d printed one can also use a 40x40mm fan, with the advantage that it provides better airflow at lower noise levels. So we recommend a 40x40mm fan and printing the respective case. |
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2xRTLSDR Dongle with compatible cables | Recommended: Stratux V2 SDR or Nooelec Nano 2+, but any RTLSDR dongle should do, as long as it fits in the case. They are often offered in pairs already. Do NOT get one with a Bias-Tee (e.g. Nooelec SMArTee). The consume too much power. |
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1090 MHz and 2x868 MHz antenna | There are many SDR + Antenna kits available that work fine. Note that these usually come with a 978 MHz antenna, instead of an 868 MHz one. In this case, you might want to consider getting an 868 MHz antenna seperately. BEWARE: Make sure that your 868 MHz antenna has the correct SMA connector. There is a male and a female connector. If you put a female SMA antenna on a female SMA cable, it will NOT work. Additionally, an 868 MHz antenna for transmission is needed. This can be a smaller one, since the transmission power is good enough to be seen from far away anyway. |
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Micro SD card (4Gb+) | Get a decend brand one. Quality and performance varies a lot between manufacturers, so get something decent, not the cheapest one available. They typically don't work well. |
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4x M2.5x5 and 4xM2x8 screws | The M2x8 screws may also be a bit longer, but the M2.5x5 ones may not. |
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1xshort/flexible Micro USB cable with small plugs | The one shown in the image can easily be found on eBay and other sources. Other cables might work as well. |
Additionally, you will need something providing 5V/2A power via a Micro USB plug (or USB-C plug if you use the Raspberry Pi 4). You can either use a cigaret lighter adapter, or a power bank, depending on your needs.
First, make sure that your T-Beam works properly. Dead on arrival devices are not uncommon with cheap headware components.
Power it up and make sure it creates a hotspot SoftRF-xxxxx. Connect to it (password 12345678) and head over to http://192.168.1.1.
A status page should come up. Place your T-Beam at a location where it should be able to get a decent GPS fix for a while and check the status page and make sure it is able to get a fix - there were a few reported cases with faulty GPS antennas.
If any of the points don't work, you might want to contact the seller.
You might also want to connect the T-Beam to your PC and check with a serial port reader (e.g. putty) that GPS NMEA sentences are received from the T-Beam (baud 38400).
To save space, we have decided to slightly modify the T-Beam to remove the 18650 battery holder, as it serves no purpose in the Stratux and only wastes space.
Desolder the battery holder with a soldering iron and remove it. If you don't have a soldering iron, some careful force and a side cutter might do the job as well.
After desoldering, make sure that the remains of the solder don't stand up too far from the PCB (<1.3mm). If needed, try to flatten them a bit with the soldering iron.
Now connect the T-Beam to your PC via Micro-USB to flash the firmware of choice. For information about firmware choice, and how to flash it, see here. You can also skip this step and flash the firmware later directly from your Stratux. Read the linked article and decide for yourself.
It is also possible to ask the seller LilyGo for a custom version of the NEO M8N T-Beam at zero additional costs:
- to change the current IPEX connector used for the 868MHz antenna to an SMA connector, add the following comment to your order "DZ338, change to SMA connector". T-Beam will then look like the below.
- also the battery holder as well as the tiny ceramic GPS antenna can be removed by the factory. Just add "remove ceramic GPS antenna, no battery holder", and the previously explained soldering part becomes obsolete.
Mount the fan to the lid. We recommend to mount it as an exhaust fan so that fresh air can be sucked in from the other side of the case to cool the RTLSDR modules
Use the M2.5x5 screws to mount the RaspberryPI, and screw in the two SMA cables to the side "wings".
Try to not bend the SMA antenna cables too much. They are a bit fragile and can break.
Plug in the two RTLSDR dongles in the bottom two USB slots and connect the SMA cables to them. IMPORTANT: Your SDRs will probably be labelled "1090" and "978". The Lid of the case also has labels embossed on both sides (depending on 3D printing settings maybe a bit hard to see). Make sure you connect the 1090 SDR to the 1090 side of the case, and the 978 SDR to the 868 side of the case.
Now screw the T-Beams SMA cable into one of the venting holes on the back side (if you have the T-Beam version with the fixed SMA plug, you can skip this step. The fixed SMA plug will later line up with the holes, so it should fit right through them).
connect the fan to the 5V headers as shown in the photo. The exact pin layout can be found here: https://www.raspberrypi.org/documentation/usage/gpio/ Connect the red cable to a "5V power" pin, the black one to a "Ground" pin.
connect the T-Beam's SMA cable with the T-Beam and place the the T-Beam on top of the case, with the back-side up and the USB connector facing towards the RaspberryPi. Make sure the T-Beam's GPS antenna is on the back side aswell.
Use the short/flexible Micro-USB cable to connect the T-Beam's USB port with one of the free RaspberryPi USB ports TODO: photo
Now place the lid on top of the case. The GPS antenna should sit in the small rectangular hole in the lid. Connect all the antennas to the appropriate sides and close the case with the M2x8 screws and you are done with the hardware
You can download the latest version of Stratux EU here: https://github.com/b3nn0/stratux/releases.
There are several guides on Youtube on how to flash the software. See e.g. here: https://www.youtube.com/watch?v=fJmMdIvb8zE.
Of course, make sure to use the image of the EU version, not the US version shown in the video.
After you have flashed the software onto the Micro SD, put it into your Stratux and you are good to go. Boot up your Stratux and it will create a WiFi hotspot called "stratux" for you. Connect to it, and then open http://192.168.10.1 in your browser to get started. If your T-Beam is running the OGN Tracker firmware, you should be able to remotely configure it form the Stratux web interface.
- You can add a Stratux AHRS module to get a barometric altitude (i.e. more precise relative traffic altitudes) and AHRS data (TODO: no guide yet)
- You can add a BMP280 breakout board to get barometric altitude, see here
- You can add a GY91 board to get AHRS (TODO: no guide yet)
- You can add a serial adapter to connect to devices that only support serial traffic data: https://github.com/b3nn0/stratux/wiki/Stratux-Serial-output-for-EFIS's-that-support-GDL90-or-Flarm-NMEA-over-serial