Chelmsford 434 MHz STEM Balloon Launch

Radio amateur Chris Stubbs M6EDF will be launching one of his 434.300 MHz USB trackers on a 100g Pawan – Cheapo 11 – for a school in Chelmsford at about 1:50pm on Tuesday, May 20. Depending on altitude it could have a radio range of 500 km and the flight path will be displayed in real-time on the web.

Chris Stubbs M6EDF with 434 MHz trackers

Chris Stubbs M6EDF with 434 MHz trackers

The launch is being run as a STEM (Science, Technology Engineering and Mathematics) event for the school. In addition to the main STEM objective the launch is also being used as a charity fundraiser. You can buy a £1 ticket to “Guess the location” of the burst with money raised going in aid of The Brathay Trust, Cancer Research and Havens Hospice.

Tracking of the 434.300 MHz signal would be greatly appreciated by both Chris and the students at the school.

Balloon flight details:
Callsign: CHEAPO-11
Frequency: 434.300 MHz USB
Mode: RTTY 7N2 50 baud 450 Hz shift
Location: Chelmsford, UK
Date: 20/05/2014
Time: 1:40PM

Chris took the amateur radio Foundation training course run by the Chelmsford Amateur Radio Society (CARS) in January 2013. He is keen on both electronic construction and software development and combines the two interests in High Altitude Ballooning (HAB). Chris has built many tracker payloads for his balloon launches which usually take place from Danbury Common near Chelmsford.

M6EDF CHEAPO Micro TrackerDetails of his high-altitude ballooning hardware and experiments are online at

See online real time tracks and frequencies of this and other 434 MHz balloons at

Beginners Guide to Tracking using dl-fldigi

The role of these 434 MHz balloon launches in teaching maths and science was recently recognised by the Department for Education (DfE) see

Listen to balloons online (when in range of south-east UK) from anywhere in the world with the SUWS 434 MHz WebSDR (select USB)

Check the #highaltitude IRC channel for launch chat. A web client is available at

To get up-to-date information on balloon flights subscribe to the UKHAS Mailing List by sending a blank email to this address:

The Chelmsford Amateur Radio Society run training courses for those wishing to get their amateur licence. To find out more speak to Clive G1EUC on
Tel: 01245-224577
Mob: 07860-418835
Email: training2014 at

What is Amateur Radio ?

Post Launch Update:  The launch from The Sandon School was successful and reached an altitude of 27,000 metres before the balloon burst and the payload descended by parachute. The payload was recovered from a freshly ploughed field near Wisbech.

The signal from CHEAPO 11 could be received across much of British Isles and into Germany

The signal from CHEAPO 11 could be received across much of British Isles and into Germany