Heltec Wireless Tracker Files

[John Laidler]

In a recent post I mentioned that with a lot of help from Ross G6GVI I managed to get a Heltec Wireless Tracker running Horus Binary V3.

The original code came from Roel and can be found at  https://github.com/RoelKroes/TBTracker-ESP32/releases/tag/V0.5.3

If you download and unzip these files there are two which need to be modified for the Heltec board: the Settings file and the .ino file.  The enclosed Settings file has the correct pin numbers for the Heltec and has been successfully used on version 1.2 boards. The file has lots of comments so you can see what needs to be adjusted. For example, where it shows "NOCALL" this is where you add your callsign. There is also a line to reduce the CPU speed to save battery power.  It is enabled in this copy but you can change it.  It tried a lower CPU speed than 40 MHz and though it transmitted something it couldn't be decoded. There is also a line to alter the power, which is currently set at 10mW but it can be increased to 20mW but my reading of the UK ISM rules for the frequency I was using (9434.714 MHz) was power was limited to 10mW. I'm probably wrong but this setting was used on the recent flight and there did not seem to be any problem with range, with successful reception at up to around 300Km.

The .ino file has only one change, starting at line 411 are 3 lines to turn on the GPS.

The program can do a lot more than Horus Binary including LoRa and APRS but I have only tested it on  Horus Binary V3.

I bought my boards from AliExpress and had two which seem to have defective GPS units. When ordering ensure you buy the right frequency as there are 868 and 915 versions as well.  I thought there were also UK sources but when I checked the only sellers I could find had 868 boards for MeshTastic. If you can find a seller with 434 boards it might be worth paying the extra so you could return a defective one more easily. To tell a 434 board from a 868 board look underneath between the LoRa and GNSS antenna connections where you will see RLF and RHF written. If it is a 434 board there will be a small surface mounted resistor opposite RLF.  868 and presumabely 915 boards have the resistor opposite RHF.  Sadly, the resister is just a means of identification - you can't change the board by moving it.  I believe this has been (unsuccessfully) tried!

John

M0WIV

[John Laidler]

Just to add there are a couple of typos in my last message, the main one was the frequency used was 434.714 MHz not 9434.714 MHz! 

I should also add if you have a 968 MHz board it will work on 434 MHz but transmit very weakly but enough for testing on the bench to see if a receiver is working.

John

M0WIV 

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[Nick McCloud]

On Monday, 27 April 2026 at 18:17:30 UTC+1 John Laidler wrote:

 To tell a 434 board from a 868 board look underneath between the LoRa and GNSS antenna connections where you will see RLF and RHF written. If it is a 434 board there will be a small surface mounted resistor opposite RLF.  868 and presumabely 915 boards have the resistor opposite RHF.  Sadly, the resister is just a means of identification - you can't change the board by moving it.  I believe this has been (unsuccessfully) tried!

There are no traces to these resistors, so it's not about trying & failing, this is normal practise in the LoRa community for any number of RF boards that looks the same on the surface. 

However, the SX1262 can do both ends of the frequency range so nothing stopping you programming it, it's the low pass filter that tends to differ. If you want to do SMD surgery, you could remove the LPF and put your own in. Not recommended just for the level of faff.

However Heltec are in the process of making all new exciting special boards, now with extra power output for any culture that needs things to be big, like cars etc. These are a whole bag of WTF, the latest ESP32 LoRa v4 has had some radical changes in the RF output stages. There are no docs on controlling the RF PA or any sample code.

In short Tracker v1 or LoRa v3.2 good, anything else at this point in time is work in progress.

[John Laidler]

To add to my first post it may be useful to record the versions of a couple of libraries which I used to compile the sketch.

RadioLib  ver 7.6.0

Heltec ESP32 Series Dev-boards ver 3.3.8

Of course it may work with later versions but these were the ones I used.

John

M0WIV

On Monday, 27 April 2026 at 18:17:30 UTC+1 John Laidler wrote: