LORA GPS Beacon for high altitude ballooning

A light weight, low power LORA GPS Beacon for high altitude ballooning and other tracking duties.

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I wanted to find out how Long Range LORA is. I had a HAB flight coming up and decided to give it a try. It shows promise and opens the door to more interesting stuff.

I like flying high altitude balloons (HABs) .  The normal mode of operation is APRS on 144.390 MHz and sometimes a secondary UHF APRS beacon is used.  This is limited to 1200 baud and the available beacons can be heavy and/or expensive.  Also you have to be a licensed amateur radio operator to control the APRS beacon.  LORA is unlicensed and may open up HAB'ing to the unlicensed.  Most of the beacons don't have easily accessible I/O for sensors and controls.  The LORA gear comes as transceivers so control of HAB functions are possible.

For this try I had just a few days, so I ordered Adafruit Feather LORA boards and GPS shields.  Combined with a 2000 mAh Lipo battery the beacon weights in at about two ounces.  I 3D printed a little case for it and will string it on the flightline.  The case adds about an ounce for a total of three ounces.   Both the m0 and 32u4 Feather versions were tested.  The 42u4's have sufficient throughput for the task and they do use less power . 

I chose a 2000 mAh battery in hopes that the beacon will remain in operation for days if needed.  Sometimes it is and most of the commercial beacons have a run time of a day or so.

Currently I am sending the GPS sentences with CR/LFs so they display nicely and should feed some software.  I hope I don't have to convert to APRS messages - too much work.

For the beacon I am using a 6.5" piece of stranded silicone wire as a 434 MHz quarter wave whip and for the receivers I mounted the SMT uFL connectors on the Feather boards and will use mag mount roof top antennas while chasing.

I am using the RadioHead library for LORA and am trying to parse the GPS sentences to make them more readable.  So far the Adafruit GPS library is fighting with RadioHead.  The examples programs suggested 434 MHz so I tried listening on an RTL/SDR and a handheld ham radio.  It is pretty quiet there to my surprise.

The LORA link is running at it's slowest rate with BW = 500kHz, coding = 4/8, spread = 4096 chips/symbol.

I am sending complete NMEA RMC sentences and using PC software to plot the beacon's location.   I also have the receiver software output the sentence and RSSI to a  log.

The code for becon/receiver and .STL for box will be posted soon.  The box will be redesigned for more thermal insulation. I am going to fly the beacon soon and will post a date/time and location for the launch and predicted flight path. At it's apex the HAB  will have a ~425  mile range circle.


Message display segment runs on 32u4 or M0 Feather/LORA module

ino - 3.83 kB - 07/22/2020 at 03:05



GPS to LoRa segment runs on GPS modules & 32u4 or M0 Feather/LORA module

ino - 4.48 kB - 07/22/2020 at 03:04


  • First Flight - March 8, 2020

    Martin03/09/2020 at 16:42 1 comment

    We flew a 3,000 gram balloon filled with almost 200 cubic feet of hydrogen.  The plan was to reach 126,000 feet but we only made it to 119,323 feet.

    The balloon flew a primary VHF APRS beacon with a twinlead dipole antenna.  The payload landed on the VHF antenna and couldn't be heard.  The LORA beacon continued operating and lead us to the payload.

    I recorded the LORA beacon with my home base station and received most all of the packets until the end.   I also copied from my car with a mag mount.  All communications stayed above -90 RSSI and the system is supposed to operate down to -120.  The beacon antenna was just a 6.5" piece of wire.

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Martin wrote 08/20/2020 at 16:46 point

Did you change the link parameters like suggested?  (BW = 500kHz, coding = 4/8, spread = 4096 chips/symbol)

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Fabio wrote 08/15/2020 at 23:53 point

Hi Martin, great project! I am also working with LoRA for my HAB project.  Seems to work pretty well,  however I was not able yet to test communication in direct line of sight, without obstacles.  I can  successfully receive and decode LoRA packets from about 2KM with buildings and trees in between, and  just a wire on both transmitter and receiver. I guess with a better antenna on the base receiver the range should improve. 

But in any case I am far from a 30KM range which is the approximate altitude my balloon will get.  I would love to know how was your experience and the tests you made before your flight.  Any advice would be appreciated!  Thanks!

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