Monday, April 15, 2024

APRS over Lora 433MHz

Completed portable tracker. 

With recent advancements in Lora, and the cheap boards on the market due to Meshtastic, I started researching into APRS over Lora. I found that several locations are already using this method in the EU, as well as here in the states. Specifically, I noticed a lot of activity around the Denver area. I reached out to Ham Radio Operators that were sending APRS packets over Lora using the iGates in their area, and they pointed me to an updated firmware by CA2RXU. I did run into some problems getting my device operational, and I am hoping these companion instructions will help others get started with APRS over Lora. 

What is impressive about APRS over Lora, is how well it works, and only 1 watt, while on a UHF frequency. Lora can be in the background noise, and still be heard by the sensitive receivers, making extreme distance possible on minimal power. 

Some minor picket fencing of the signals still occur which is expected, but overall this still appears to work extremely well. iGate setup with a Diamond VHF/UHF antenna 15' AGL, while the mobile used a simple mag mount antenna.

APRS over Lora is starting to be used more in the US. 

These are the firmware download links:

Detailed configuration info:

I got started with Heltec V3 for the hardware. These can be purchased directly from, but shipping times are longer. They are also available from Amazon for faster shipping, but higher cost:

Heltec v3 ($26)

5db 433MHz SMA Antenna ($7):

iGate Case Only:

Tracker Parts Only:
GPS Module (~$9.50 Each):

3000mah Lithium Battery (~$7.25 each):

433Mhz Mag Mount Antenna ($15):

3D Printable Case:

This makes for a total of each device:
iGate - ~$30 (Using Ham radio antenna)
Tracker - ~$43 (standard antenna)

iGate Setup:
Once at least the Heltec v3 kit is in hand, its easy to build an iGate because of the available firmware. Download VStudio, and open the extracted zip folder of the firmware.

Make sure you have an antenna hooked up to the board before plugging in any USB cable to power it. Select the correct board type that will be used. Now, the firmware is in 2 parts, the main code, and the Filesystem. If both are not uploaded, the firmware will not start. (Do not modify the firmware files, only set the board type).
Install PlatformIO extension

Once the firmware is loaded, the iGate will start its own Access Point for configuration.

Connect to "N0CALL AP", with 1234567890 as passcode. Access, to set to the settings of iGate initially.

Change the Callsign, and add APRS code for APRS-IS.
Add a WiFi network for the device to connect to, and then save the configuration. 

Device will reboot and start gating traffic to APRS-IS. Hook up an external antenna if possible to improve the range.

Completed and operational iGate at home. 

Tracker Setup:
The same process is needed for the tracker, but a file will need to be modified for the callsign. 

Not required, but if you want to add a buzzer, the pins need to be selected, and options enabled. These are the settings I am using on my Heltec v3 tracker. Other devices will have different pinout numbers.

TX -> GPIO48
VCC -> 3.3v

- -> GND
+ -> GPIO33

Solder the wires for the GPS first (3 wires), and install into case. Then add the SMA connector. Careful with the case, you should not need to make the hole bigger unless 3D printer is not calibrated correctly. 

This case fits the larger battery, which should last a very long time.

Detailed view of inside the case. 

Be sure the main code as well as the file system is uploaded to the device.


No comments:

Post a Comment