UBSEDS21 Balloon To Test 145.825 MHz APRS

UBSEDS18 Solar Powered Balloon

UBSEDS18 Solar Powered Balloon

On Sunday, December 11 Bristol SEDS students launched UBSEDS21 a 434 MHz Contestia and 144/145 MHz APRS solar powered balloon that may travel around the world.

Update Dec 23: UBSEDS21 over Spain having completed its first circumnavigation of the globe see track.

Update Dec 20: APRS creator Bob Bruninga WB4APR reports receiving @bristolseds UBSEDS21 balloon AD6AM-13 145.825 MHz Dec 20 1420 EST – Bob was Mobile in Annapolis MD.

Update Dec 18: UBSEDS21 has crossed the Pacific and reached Canada.

The UBSEDS21 balloon was built from 50 micron thick PA-EVOH-PE multilayer film and is about 1.9 meters in diameter, the payload weight was 34.2 grams.

After launch on December 11, 2016 the balloon achieved a stable altitude of 15.2 km flying in an easterly direction on its potential circumnavigation of the globe.

The initial plan was to use UBSEDS21 to contact the International Space Station (ISS) via APRS on 145.825 MHz. However, the VHF radio on the ISS is out of order, so this flight is used to test the amplifier and hopefully talk to any APRS enabled satellites.

The winter launch means the payload needs to deal with the sun staying low above the horizon during the day. For this reason, sideways facing solar panels were used.

Original post Dec 9:

Another pico launch from Bristol this Sunday, December 11 between 0500 and 0530 GMT. This launch is using a 1.9m envelope and longer payload train, and so we have a NOTAM in place. The flight is predicted to head south-east towards France.

The payload will be transmitting Contestia 16/1000 on 434.610 MHz USB. Each transmission of Contestia 16/1000 will be preceded by 10 seconds of pips and RSID.

The Contestia transmission rate will be once every 30 seconds during launch and when power is available during the day. Otherwise the transmission rate will be once every 2 minutes. Hopefully the tracker will operate from dawn to dusk, and maybe also during the night.

The tracker will transmit APRS outside countries where the amateur license is not permitted airborne (like the UK). Additionally it will test APRS on 145.825 MHz, with an output power of +26 dBm (400 mW).

More details will appear on the website

Many Thanks,

Richard Meadows M0SBU
Bristol SEDS

High Altitude Balloon tracking and information links

Richard M0SBU took the amateur radio training courses run by the Chelmsford Amateur Radio Society (CARS) at Danbury in Essex. Further information on the courses is available from the CARS Training Coordinator, Christopher G0IPU
Tel: 07908-107951
Email: training2017 at

What is Amateur Radio?
Find an amateur radio training course near you

Sandringham School aims for space

Sandringham students operating the GB16YOTA amateur radio station, Dec 1, 2016

Sandringham students operating the GB16YOTA amateur radio station, December 1, 2016

Students at Sandringham School plan to launch a High Altitude Balloon with a Raspberry Pi payload into near-space and transmit back pictures.

The downlink from the balloon is expected to be in 434 MHz and at the maximum 30 km altitude the radio signal should have a range of up to 800 km enabling reception by radio amateurs across the British Isles and into Europe.

The launch is planned for Science Week, March 13-17, and the students will use the download data they collect from near space for analysis and use in lessons.

Earlier this year Sandringham students used amateur radio to talk to UK astronaut Tim Peake GB1SS on the International Space Station, see

Further details on the balloon launch at

HAB Flight Launch Assembly leaflet

What is Amateur Radio?

Find an amateur radio training course near you

A free booklet is available aimed at introducing newcomers to the hobby that can also be used as a handy reference while getting started, see

UK student balloon crosses Pacific

UBSEDS18 Solar Powered Balloon

UBSEDS18 Solar Powered Balloon

The UK balloon UBSEDS18 carrying payloads for APRS and 434 MHz has successfully crossed the Pacific, on the same day a USA amateur radio APRS balloon crossed the Atlantic.

The solar powered UBSEDS18 was developed by students from Bristol University and launched on Wednesday, August 17. Since then it has traveled in an easterly direction for 20,252 km completing the Pacific crossing on Thursday, September 1, 2016.


The amateur radio APRS balloon CNSP30 was launched from California on August 25 and on September 1 crossed the coast of northern France. Its APRS signal was receivable across central and southern England.


Richard Meadows M0SBU, who worked on the development of UBSEDS18, took the amateur radio training courses run by the Chelmsford Amateur Radio Society (CARS) at Danbury in Essex. Further information on the courses is available from the CARS Training Coordinator, Christopher G0IPU
Tel: 07908-107951
Email: training2016 at

UBSEDS19/20 balloons launch from Bristol

UBSEDS IMG_2406Richard Meadows M0SBU reports two high altitude balloons carrying 434 MHz payloads will launch from Bristol on Monday, August 29. There will be Slow Scan Digital Video (SSDV) transmissions.

Online real-time tracking of UBSEDS balloons!mt=roadmap&mz=8&qm=3_days&q=UBSED*&f=UBSEDS20

We’re planning the first launch of ‘pico-pi’, our Raspberry Pi Zero based tracker, from Bristol this Bank Holiday Monday, August 29 between 0500 and 0530 BST. This launch is using a 1.9m envelope and longer payload train, and so we have a NOTAM in place.

There’s more information about the tracker itself here:

The combined payload mass will be about 70 grams, and the attempted float altitude will be about 13 km. This is our first launch of this setup, so it seems unlikely that everything will go to plan!

First is the UBSEDS19 backup tracker, which is powered from a single AAA Lithium Energiser battery. It transmits Contestia 16/1000 with pips and RSID on 434.615 MHz USB, once per minute below 8km altitude and every two minutes otherwise. The battery is expected to last a few days.

Next is UBSEDS20, which is the experimental Raspberry Pi Zero board. This is powered from solar panels only, and hence is only expected to operate continously after about 0830 BST (before this it may transmit without a GPS lock, as the Raspberry Pi and GPS are powered down).

– 434.610 MHz USB: 300 baud RTTY, 850Hz shift, 8N2 transmitting telemetry and SSDV. There is also Contestia 16/1000 with RSID on this frequency. If you are listening to the RTTY, remember to turn off the ‘RxID’ button on the top right of dl-fldigi.

– 869.85 MHZ LoRa ‘Mode 3’ (250kHz / SF7 / EC4:6, explicit header), transmitting SSDV with the callsign ‘UBSEDL’. This frequency is only active in Europe. Many thanks to Dave Akerman M0RPI for making his work on LoRa available for us to use, including the lora gateway.

Rather than the usual JPEG SSDV, this payload is transmitting Better Portable Graphics (BPG) images. This is experimental, and doesn’t support it just yet. Hence receivers should upload to instead, please read the instructions on this site. You’ll need dl-fldigi release 3.2 and slightly modified LoRa gateway, as explained on the site. The dl-fldigi release can be found here:

Many thanks to everyone who attempts to track these.

Richard Meadows M0SBU
Bristol SEDS

Useful balloon links

Richard took the amateur radio courses run by the Chelmsford Amateur Radio Society (CARS) at Danbury in Essex. Further information on the courses is available from the CARS Training Coordinator, Christopher G0IPU
Tel: 07908-107951
Email: training2016 at

UKHAS Conference Cambridge


SSDV picture from a PIE balloon – Image credit Dave Akerman M0RPI

There’s an impressive line-up of radio amateurs among those giving presentations at the UK High Altitude Society (UKHAS) conference in Cambridge on Saturday, September 10, 2016.

Watch Live at


The conference takes place at the Institute of Astronomy, University of Cambridge and attracts those interested in learning about building and flying High Altitude Balloons or in tracking their 434 MHz signals.

Tickets can be purchased from the wiki page and cost just £10 each.

Provisional Schedule as at August 16:
09:30     Assembly – Drinks & Biscuits
10:00     Welcome & Introduction
10:10     LoRa – Dave Akerman M0RPI
10:40     Evidence that Biology is Continually Arriving to Earth from Space – Prof Milton Wainwright (Univ. of Sheffield)
11:10     Operation Outward – Steve Randall G8KHW
11:40     Break
12:00     Chase & Recovery – Dave Akerman M0RPI
12:30     VORTEX Parachute Tests – John Underwood
13:00     Lunch
14:00     CUSF’s Martlet Rockets – Adam Greig M0RND
14:30     Introducing AirCores – Dr Johannes Laube (UEA)
15:00     Scheduled Talk Subject to Official Approval
15:30     Break
15:45     500 cu m Solar Balloon Project – Sven Steudte DL7AD
16:15     Superpressure Maths & Envelope Construction – Richard Meadows M0SBU (UBSEDS)
16:45     End

UKHAS were offering the option to complete the amateur radio Foundation Practical Assessments and Exam at the conference. This was rapidly fully booked, perhaps a sign of the shortage of Foundation exams venues.

If you would like to speak or run a workshop, please do get in touch with either Daniel Saul M6DSA or Steve Randall G8KHW. Contributions don’t need to be directly linked to ballooning and they look forward to all suggestions.

Conference registration information is at

Probable UKHASnet launch May 21/22

UKHASnet LogoJames Coxon M6JCX reports he is hoping to launch a UKHASnet node from East Anglia this weekend.

On the UKHAS Google Group he writes:

I’ve put together a GPS enabled, temperature controlled node AJ2 which will be launched on a latex balloon (rather than pico).

Due to the pattern of the winds the aim will be to float the balloon at around 30-35 km and current predictions suggest that it’ll drift east first then turn around and come back across the UK travelling west. This should give pretty good coverage of the UK and at a push across the sea towards the Netherlands so it would be great if any UKHASnet nodes could be brought online.

The node itself will be in repeater mode as well as transmitting its own packets every 30 seconds with GPS and other data. Previous tests and flights have had a mixture of results, the EMF launch allowed for 65 km downlink range and recent tests on the IoW made a solid 2 way link over 18 km however other flights haven’t been successful. Hopefully the temperature control will stabilise the radio to stop it drifting too much (both on tx and rx) and the node will recalibrate its noise floor etc as well as reset the rx loop of the radio to stop it locking up (a previous issue). The more nodes that we can have online the better (it is even possible to setup an RTLSDR dongle as a UKHASnet gateway)

There will be a backup tracker providing a RTTY downlink on 434.300 MHz (Atlas) which will be uploaded to This will be RTTY, ASCII 7, 425 Hz shift and is an old pAVA R7 board with a RFM22 so be prepared for some drift.

Current plan is to launch around 1100 on Sat 21/05/16 though the window will be the whole weekend and launch will be from Preston St Mary, Suffolk.

Flight data will be on the UKHASnet map

I’ve made a grafana page for the node
and as always there will be discussions on #ukhasnet on freenode.



Useful High Altitude Balloon links