Project Horus High Altitude Balloons: Horus 55 Flight Report

Horus 55 was the culmination of something that had been discussed for many years within the Project Horus team – Live video from a high-altitude balloon. The technical challenges in doing this are many, from designing a transmitter system that provides enough signal without melting in the thin atmosphere at high altitudes, to building a high performance receive system that can capture that signal, and then upload it to the internet for everyone to enjoy. (After all, if it didn’t get live-streamed, did it really happen?)

At 10:30AM on the 7th of March 2021, all of this came to fruition with the first flight of the Project Horus DVB-S payload.

The Payloads: DVB-S Transmitter

The DVB-S payload was the primary experiment on this flight, and had been in development by Mark VK5QI and Peter VK5KX over the last 12 months. The payload utilised a Raspberry Pi Zero W to capture and compress video (using F5OEO‘s DVB-S encoder and natsfr’s LimeSDR Gatewarethis project would not have been possible without their work – thanks!), which was then modulated as a 70cm (445MHz)  DVB-S transmission using a LimeSDR Mini. The signal was amplified to ~800mW using a LDMOS-based power amplifier. The overall power dissipation in the payload was ~6 watts, so a heat-spreading and heat-sinking system was built by Peter, including custom-milled interface plates for the LimeSDR.

Monitoring the temperature of the LDMOS device during testing.

The payload was powered from 8x Energizer Lithium AA primary cells, which are well-regarded for their low-temperature performance.

Much testing and tuning of the payload was performed in the lead-up to the launch, including monitoring of the temperatures within the payload when sitting in full-sun, to ensure it would not reach dangerous temperatures.

Mark VK5QI gave a presentation on the payload at the AREG February meeting, which is available here:

The final DVB-S parameters used on the flight were:

  • Frequency: 445.0 MHz
  • Mode: DVB-S
  • Modulation: QPSK, 1 Msps
  • Forward-Error-Correction: r=1/2
  • Video Resolution: 720 x 404

The Payloads: LoRaWAN Beacon

Horus 55 LoRaWAN PayloadAlso on this flight was an experimental LoRaWAN tracking payload built by Liam VK5LJG. The aim was to transmit position beacons into ‘The Things Network‘ (‘TTN’), which has gateways (receiver stations) in many locations across Australia.

The payload operated on the 915-928 MHz LIPD band, with a transmit power of ~50mW. The hardware was a RAK Wireless RAK5205 board, running custom firmware for the flight. Position updates were only sent every ~3 minutes to comply with TTN fair-usage guidelines.

We expected that this would be received by TTN gateways all around the Adelaide area… it actually performed much better than expected!

The Payloads: Tracking & Flight Management

Reprogrammed RS41

The flight also included the usual complement of telemetry and flight management payloads. Primary telemetry was provided by a reprogrammed RS41, transmitting the ‘Horus Binary‘ 4FSK mode on 434.200 MHz. This was received by a large number of amateur stations running the ‘Horus-GUI’ demodulation software. Tracking of the payload was available on the HabHub tracker online, allowing global access to the position of the balloon throughout the flight.

The separate flight management payload was a LoRa-based payload operating in the 70cm (430.0MHz) amateur band. This payload allows remote termination of the flight if necessary (and it was actually used in anger this flight!).

Flight Preparation & Receiver Testing

VK5APR Receiving DVB-S SignalsOn the weekend prior to the launch, two test-and-tune events were conducted, where receiving stations around the Adelaide area had the opportunity to configure and test the software and hardware necessary to receive the DVB-S signals. Transmissions were conducted from Steve VK5SFA’s QTH on Saturday, and from Black-Top Hill on Sunday. Both sites provided excellent line-of-sight to the Adelaide metropolitan are, enabling eight stations to be able to receive the test  transmissions ready for the live balloon flight the following weekend.

Testing the Ground-Station AntennasFinally, a full systems check was conducted with Peter VK5KX. The test covered all of the equipment which would comprise the primary ground-station for the flight, receiving video from the payload and streaming it live to Youtube. This involved testing of the 2 x 18-element Yagi-Uda array, and all the receiver and streaming software. A big thanks to Hayden VK7HH for helping get the Youtube streaming working via his HamRadioDX channel.


The ground station crew, chase teams, and spectators started to assemble at the Auburn Oval launch site around 9AM, to find that showers had set in.

It was decided to continue on with launch preparations and wait for the showers to pass.

By a bit after 10AM the showers had died away to a light sprinkling, and the balloon filling was started. Around this time the live-stream from the launch site was switched on, with many viewers from around the world tuning in to watch the proceedings.


The balloon used for this flight was a Totex 1000g, and an entire 3.5m^3 cylinder of helium (donated by the University of Adelaide) was used to fill it. Using the fast-fill rig the fill was completed in a few minutes (as opposed to the almost 1 hour of slow-filling that used to be required), and the balloon was tied off ready for launch.

After a final check that all payloads were working as expected, the (short) countdown began, and the balloon and payloads were released!

Ascent & Live Video!

After launch the ground-station system was switched into ‘auto tracking’ mode, and began pointing the high-gain Yagi antennas to follow the balloon and payloads. This ensured the best quality video reception, and it definitely worked!

DVB-S Received by Joe VK5EI after launchViewers at the launch site and all around the world via Youtube were treated to clear visuals relayed from the primary ground station as the balloon ascended up to cloud-base. Reports from other receiving stations around the region started trickling in, with Ian VK5ZD (near Kapunda) and Joe VK5EI (Adelaide) being the first to report in.

As the balloon reached the first cloud layer the views of the surrounding landscape was replaced with grey, and the chase teams took this as a sign that it was time to head off towards the expected landing area. Meanwhile the ground control team of Matt VK5ZM, Pete VK5KX and Grant VK5GR kept watch on the balloon state and the TV signal being relayed to YouTube and being broadcast around the globe.

The ground-station team continue to keep tracking the payload, uploading live video to over 200 viewers on Youtube. A big thanks to Hayden VK7HH for hosting the live stream on his Youtube channel, and helping answer the many questions that were asked by the viewers throughout the flight. Please make sure to Like and Subscribe his Youtube channel!

One of the last shots received before the balloon was cut away so the payloads could land

Chase, Cutdown & Recovery

Chase cars stopped at EudundaThis flight had four chase teams:

  • Mark VK5QI  and Will VK5AHV
  • Darin VK5IX, along with Cameron and Dan
  • Liam VK5LJG
  • Gerard VK5ZQV

All the teams headed off in convoy towards Eudunda as their first stop, where the traditional bakery visit was made mid-flight instead of after recovery.

Receiving DVB-S from Mark's carMark and Will were receiving the video from the DVB-S payload in the car, which worked surprisingly well even with the fairly modest antenna setup on Mark’s car (an upward-fading turnstile).

Tracking the balloon flight-path in the chase car

After a quick lunch, the teams headed south towards the predicted landing area. As the flight processed and the balloon rose past the expected burst altitude of 30km, Mark made the call to terminate the flight to help land the payloads in an easily recoverable area. A few radio commands later, the payloads started falling, with the cut-down event observed via the video link (though the fast tumbling did result in a lot of broken video). The maximum altitude achieved was 32379m above sea level.

The teams headed towards the new predicted landing location, and after a bit of back-and-forth were able to be in position to watch the payloads land under parachute. Unfortunately the payloads were just a bit too far away for the teams to get imagery of the final descent.

After getting permission from the landowners (thanks!), the teams were able to enter the property and drive almost right up to where the payloads had landed.

Landed payloads While a bit bent and dented (and upside-down!), the DVB-S payload continued to transmit video after landing, with the receiver in Mark’s car capturing the team walking up and recovering the payload.

Bent payload

Analysis of log files from the payload showed that overheating was certainly not an issue – instead the heat-spreader plate within the payload reached a chilly -27˚C during the descent phase of the flight!

DVB-S Payload Temperatures

DVB-S Reception Reports

So far the following stations have reported being able to receive video from the DVB-S payload:

  • Bill VK5DSP – Middleton, SA
  • Iain VK5ZD – Kapunda, SA
  • Joe VK5EI – West Lakes, SA
  • Berndt VK5ABN – Nairne, SA
  • Andrew (N0CALL), Pt Noarlunga, SA
  • Steve VK5MSD – Whyalla, SA
  • Roger VK5YYY – Whyalla, SA
  • Gerard VK5ZQV – Mobile, during the chase.

If you received video from this flight, let us know!

The longest distance the payload was received from was by the stations in Whyalla, at almost 190 km range, followed by Bill in Middleton, at 145km range. The payload designers are absolutely ecstatic at how many stations were able to receive video during this flight – hopefully we can repeat this success on more flights in the future!

Horus Binary (4FSK) Telemetry Reception Statistics

With every Project Horus flight we like to thank all the receivers that helped receive telemetry from the flight. All the telemetry you receive and upload to the net helps keep the tracking map up-to-date throughout the flight, and serves as a backup in the case of ground-station or chase-car receiver failure. On this flight telemetry was recorded from as far away as Horsham, though there were reports of telemetry reception in Melbourne – however it appears these stations did not upload their telemetry to the internet.

Horus 55 Callsign Pie

CallsignReceived PacketsPercentage of Flight ReceivedFirst-Received Altitude (m)Last-Received Altitude (m)
VK5LJG (Home)138169.7%29463156

LoRaWAN Experiment Results

As mentioned earlier, the LoRaWAN payload was transmitting telemetry packets to be received by The Things Network gateways. We expected the payload to be received by stations in the general Adelaide area, however it turned out that at the peak of the flight we were received by gateways as far away as Ballarat, Victoria! Full details on what gateways received each packet are available here.

LoRaWAN Coverage

The longest path was 585km, which for a ~50mW transmitter at 923 MHz is quite an achievement! The world record distance for this system is 823km, and we’re interested to see if we can beat this on a future launch!

Flight Track

At the conclusion of the flight we were also able the telemetry into this flight profile, which gives an appreciation of the journey the balloon and the experimental TV transmitter under took.

Conclusion & Future Flights

Horus 55 - Flight Statistics

Flight Designation:Horus 55
Launch Date:2021-03-07 00:02Z
Landing Date:2021-03-07 02:37Z
Flight Duration:~2.5 hours
Launch Site:-34.02932,138.69124
Landing Site:-34.25959,139.11443
Distance Traveled:46 km
Maximum Altitude:32,379 m

With the huge success of this flight, the team plans to follow this up with more video flights in the future. There are many lessons to be learnt from this flight, and many improvements that can be made to both the payload, the ground-station, and the live-streaming systems. Viewers can look forward to higher quality video, more running commentary, and hopefully live video from the chase-cars as they recover the payloads.

The next few months will be getting busy for the Amateur Radio Experimenters Group, with the upcoming Riverland Paddling Marathon taking up a lot of club members time. Expect the next full-scale flight sometime in late June – weather permitting!

Horus 55: Digital ATV Flight an outstanding success!

It is late and we are still processing telemetry and video streams but we thought we would post a quick note to say that Horus 55 was an absolute success. Stories are coming in from across the region from people who successfully watched the Amateur TV signal live over 80-90km away.

Reports also of the primary 434MHz 4FSK telemetry beacon being received 700km away in Melbourne plus the LoraWAN Things Network gateways over 560km away reporting packets from the experimental LoraWAN payload on 923MHz ISM.

We will post a long form story in the next day, but here is one of the amazing frame grabs from the TV transmitter just after burst. As the TV payload started to tumble it sent back this frame showing all of the telemetry transmitters and the parachute in one shot!

Finally here was the moment the chase and recovery crew picked up the payload.

Horus 55 Balloon Flight: D-ATV Launch Tracking & Live-Stream Details

The DVB-S high-altitude balloon launch (hopefully the first of many!) has now been locked in for 10AM ACDT Sunday the 7th of March (2330z Saturday 6th), from the Auburn Oval. The launch team is expected to arrive on site starting 9AM, and spectators are welcome!

Tracking of the flight will be available on the Habhub tracker or should be visible here on our website!

For those without D-ATV receiving equipment, AREG is going to attempt to stream the received ATV pictures via Hayden VK7HH’s HamRadioDX YouTube channel at the same time. You will find the link to the YouTube broadcast here:

Tracking Details – Primary Telemetry – 434.200 MHz

The primary tracking telemetry will be transmitted on 434.200 MHz using the Horus Binary 4FSK data mode. Amateurs in the Adelaide and Central SA region are also encouraged to get involved with the flight through receiving and uploading flight telemetry from our 70cm band tracking beacons. Every piece of telemetry data is valuable to the flight tracking and recovery teams so if you can help join the distributed receiver network to collect that data you will be making an important contribution to the project!

If you try receiving the telemetry from this flight, you’ll need a SSB-capable 70cm receiver (or a SDR), and the Horus-GUI telemetry decoder software. A brief guide on setting this up is available here:

Note that you will need to use a ‘dial’ frequency of 434.199 MHz for the 4FSK signal to be centred in your receiver passband and hence be decodable.

Tracking Details – DVB-S Video – 445 MHz

If you want to get involved through receiving the D-ATV signal direct from the balloon on 445 MHz take a look at the How-To Guide being maintained by Mark VK5QI, available here:

The DVB-S transmission parameters are as follows:

  • Frequency: 445 MHz
  • Polarisation: Vertical
  • Mode: DVB-S
  • Symbol Rate: 1 Msps
  • FEC: 1/2

Project Horus: Live ATV Flight Path Prediction & YouTube Live-stream Link

UPDATE: The launch has been set for Sunday 10AM ACDST, from the Auburn Oval. 

The flight crew are starting to get flight-path predictions for this coming weekend, though the models are quite inaccurate this far ahead of the prediction time. Currently a launch on Sunday looks promising from Auburn. This would put the balloon within 80-90km of Adelaide for much of it’s flight, which should allow many stations to be within direct decoding range of the Digital-ATV transmission on 445MHz.

These predictions *will* change over the next few days so this is just a preliminary plan at this stage. We expect to be able to make a commitment on the launch date and time most likely Thursday or Friday this week.

As a reminder, the following launch dates/times are planned:

  • PRIMARY: Sunday 7th March, 10AM (ACDT) – (2330z 6th March UTC)
  • BACKUP #1: Monday 8th March, 10AM (Public Holiday!)
  • BACKUP #2: Sunday 14th March, 10AM

For those without D-ATV receiving equipment, AREG is going to attempt to stream the received ATV pictures via Hayden VK7HH’s HamRadioDX YouTube channel at the same time. You will find the link to the YouTube broadcast here:

Digital ATV Transmission – How to Receive?

If you want to get involved through receiving the D-ATV signal direct from the balloon on 445MHz take a look at the How-To Guide being maintained by Mark VK5QI:

The setup guide is available here:

433MHz Telemetry Tracking – How to Receive?

Amateurs in the Adelaide and Central SA region are also encouraged to get involved with the flight through receiving and uploading flight telemetry from our 70cm band tracking beacons. Every piece of telemetry data is valuable to the flight tracking and recovery teams so if you can help join the distributed receiver network to collect that data you will be making an important contribution to the project!

The telemetry beacon will operate on 434.200MHz

If you want to have a go receiving the telemetry from this flight, you’ll need a SSB-capable 70cm receiver (or a SDR), and the horus-GUI telemetry decoder software ( ).

A brief guide on setting this up is available here:

Project Horus Balloon Project: Digital ATV DVB-T Terrestrial Testing – Success!

Today Mark VK5QI took the Balloon ATV transmitter out for a terrestrial test. He carried out line-of-sight testing of the DVB-S payload from BlackTop Hill to the AREG remote site near Tarlee – a distance of 54km!

First test – could he see the signal on the SDR up at the site (RTLSDR, Diamond X-50, no preamp)… yes!

Next, Mark dumped some samples with rtl_sdr, then transferred them back to his laptop. He processed them through leandvb – and got video!!! A bit of fading, but for an omni receiver with no preamp, this is a pretty damn good result!

… and here’s some of the raw video

The MER as reported by leandvb was around 8-11 dB, right on the edge of what is decodable. Still, with such a basic system, a good result!

Based on the path, it is estimated to give us a working range of about 150km from the balloon given a receiving station with 15dBi gain and a good low noise preamplifier.

Stay tuned for more information on how to receive and decode the Digital ATV signal and save the date – we hope to launch the transmitter into the stratosphere on Sunday March 7th. (We also plan on streaming the event on Youtube).

For those who missed it late last year here is a bit more information about the Balloon ATV payload and some minimum signal testing that was carried out.

Reminder: AREG Meeting this Friday – D-ATV from a Balloon 30km up!

This is a reminder that this Friday’s AREG meeting will be held at the Fulham Community Centre, Phelps Court, Fulham. Doors open at 7.15pm Central summer time with the presentation planned to start at 7.45pm.

Our guest speaker will be Mark VK5QI. He will introduce you to the new Digital ATV payload and what you need to be able to receive and decode it. More information on the presentation is available (here).

Members who can’t attend in person will be able to access the meeting via Zoom (a link will be sent on the members mailing list on Thursday). Non members will be able to watch the Youtube Livestream thanks to Hayden VK7HH and his HamRadio DX channel.

The times are:

  • 7.45pm ACDT (SA)
  • 8.15pm AEDT (NSW, ACT, VIC, TAS)
  • 7.15pm AEST (Queensland)
  • 6.45pm ACST (NT)
  • 6.15pm AWST (WA)
  • 0915Hrs UTC

We hope to see you there!

Next Meeting: 19th February: Live ATV from 30km+ altitude! How to get involved?

Project Horus began in 2010 as the brain child of a group of radio Amateurs here in Adelaide. Now, 11 years later, one of the ideas that has been discussed many times within the group is finally going to be attempted. A flight is tentatively planned for Sunday March 7th that will carry aloft our first ever digital ATV transmitter.

Live ATV from 30km+ altitude!

Adelaide from 100,000ft – Horus 12

How can you get involved?

So that as many people as possible can participate or at least attempt to receive the ATV pictures, the next meeting of AREG on Friday February 19th will feature a presentation and Q&A session with Mark VK5QI. He will take you though everything you need to know about how to receive and decode the ATV signal.

What system are we using?

For the first launch, we are going to use the following transmitter settings:

  • Transmit Frequency: 445 MHz
  • Modulation: DVB-S, QPSK, r=½ FEC
  • Symbol Rate: 1Msps
  • Video Resolution: 704×400

This will produce fairly low quality video, but will give the best chance for the payload to be received. Once we understand what the achievable signal-to-noise ratio (SNR) is for a typical flight, the symbol rate (and image quality) can be increased on future launches.

Receiving DVB-S Signals – Hardware

The most ideal way to receive signals from this payload is with a dedicated DVB-S receiver like the Minitiouner Express ( ), however it’s also very possible to receive it with Software Defined Radio receiver setups, such as the ubiquitous RTLSDR devices. You will also need a 70cm antenna with some gain, and a low-noise pre-amplifier.

While some DVB-S set-top boxes may tune down to 445 MHz, the very low bit-rates that we will be transmitting from the payload will likely be incompatible with them.

Suggested Software-Defined Radio Receivers

There’s a huge range of SDRs available which are fit-for-purpose in this application, provided you put a low-noise-figure preamp in front of them – ideally one with band-pass filtering. Examples include:

Mark testing the ATV receive across the bench

More detailed instructions and information will be posted to our website in coming days. Stay tuned!

Meeting Details

The main meeting will be held at the clubrooms, 1 Phelps Court, Fulham at the Fulham Community Centre. Doors will open from 7.15pm (ACDT) with proceedings starting at 7.45pm (ACDT) (0915z). For those unable to attend in person, we will have online options available too!

The meeting on February 19th will also be live streamed on YouTube thanks again to Hayden VK7HH and his HamRadioDX Channel.

For members unable to attend in meeting hall in person, there will be a members only Zoom channel available as well.

Links to these will be posted closer to the date!