GARC September Meeting - LoRA and RSGB High-Altitude Balloon Experiment
Grantham Amateur Radio Club will be taking part in the RSGB LoRa APRS High-Altitude Balloon (HAB) Competition on Saturday 20 September 2025. The event is being run to coincide with National Coding Week and aims to engage licensed radio amateurs in hands-on technical experimentation with LoRa APRS tracking and high-altitude data transmission.
What’s the Experiment?
The RSGB will be launching a high-altitude balloon at 11am BST from Welshpool, carrying a cross-frequency LoRa APRS digipeater. The balloon will reach an altitude of around 90,000 feet and remain airborne for up to three hours. Participants across the UK will attempt to send APRS packets via LoRa to the digipeater, which will retransmit them down to strategically positioned iGates that forward the data to the APRS Internet Service (APRS-IS).
- Uplink Frequency: 439.850 MHz
- Downlink Frequency: 433.850 MHz
- Modulation: LoRa, SF12, CR5, 125kHz bandwidth
- Power Limit: Max +23dBm (200 mW) EIRP
What is LoRa APRS?
LoRa APRS combines the Automatic Packet Reporting System (APRS) with LoRa’s long-range, low-power chirp spread spectrum modulation. Unlike traditional AFSK APRS on 2m, LoRa APRS operates on UHF bands (70cm) and enables lower power and greater reach—perfect for tracking high-altitude balloons and similar telemetry.
What Do You Need?
To take part in the experiment, participants need to build or configure a LoRa APRS tracker. The RSGB recommends using the Heltec Wireless Tracker board, which includes:
- ESP32-S3 microcontroller
- SX1262 LoRa modem
- OLED display
- GNSS receiver (GPS, GLONASS, Galileo)
- Wi-Fi and Bluetooth
You’ll also need to:
- Install Visual Studio Code and PlatformIO IDE.
- Download the RSGB-customised LoRa APRS Tracker software from GitHub.
- Compile and flash the firmware to the Heltec board via USB.
- Upload the configuration file and complete setup via the built-in WiFi web interface.
GARC’s Involvement
Grantham Amateur Radio Club members will be assembling and configuring their own Heltec Wireless Tracker units and will be discussed at the September club meeting. This session will include:
- A short presentation on LoRA and the RSGB challenge
- Help with software installation and configuration.
- Demonstrations of the device.
 A Facebook event has been created, and we’ll also run a club net on the day so members can share their results.
Tracking the Balloon
During the flight, the RSGB balloon will beacon its location under the callsign GB1HAB. You’ll be able to track it in real time using: