2m beacon

A high-flying success!

On Tuesday 2nd September 2025 we flew the beacon under a small hydrogen balloon from Bolton over the Pennines, up to an altitude of 95,000 feet (above Harrogate). After a flight of just over three hours, it landed in a stubble field, from where it was retrieved within half an hour.

Thanks to all who listened out and sent us signal reports and particularly to Ian G0CNN who's made a YouTube video. This map shows the locations of all those who sent in reports of the beacon via our online form, PSK Reporter and the Reverse Beacon Network:

The CW beacon operated on 144.091MHz, and included live temperature and pressure readings, encoded as integer values:
CQ DE G0BWC G0BWC QRPP BEACON TEST DE G0BWC IN IO83 TEMP 2560 PRES 102464
(this example indicates 25.6 Celsius and 1024.64 millibars) however the temperature readings didn't include the minus sign, and the pressure sensor was only rated down to 300 mb.

This was built by Steve G4AQB and uses an Si5351 synthesizer to generate 10 milliwatts at the bottom end of of the 2m band. With a crystal for its reference (not a TCXO), it's not stable enough for WSPR, but fine for CW reception (when the operator can manually tune in their receiver). The external board is a low-pass filter which Steve has added to reduce any residual 3rd-harmonic energy (which would appear in the 70cm band).

During tests in July and August, it was received over 50km away, but in September it was heard much more widely: thanks to local private High-Altitude Balloon enthusiast (and new BWC member) Nick McCloud, we sent it up into the stratosphere. The beacon hardware weighs just a few tens of grammes and was powered from a 6V Lithium battery pack and carried in a polystyrene box, transmitting just 10mW into a vertical dipole (the green wire) which was attached to the suspension cords under the balloon.

There are more pictures from the launch in our Gallery section and thanks to Colin G6MRY and Ian G7PAV we had video too (edited by Jack G8HIK):

As well as the 2m Amateur beacon, the flight also transmitted 2FSK (fast RTTY) and LoRa (frequency-chirp spread-spectrum) in the 434 MHz licence-exempt Low-Power Devices band, sending telemetry and slow-scan pictures. These UHF signals were picked up and forwarded by a network of Distributed Listeners, so we could follow the flight online in real-time and watch the SSDV pictures coming in.

There’s also a Grafana page which displays all the telemetry from the flight.

What goes up...

...must come down!

Page updated

Google Sites

Report abuse