FreeDV HF Digital Voice Mode: Global QSO Party April 27/28th

The Amateur Radio Experimenters Group is proud to announce a new event on the Amateur Radio Calendar. The FreeDV HF Digital Voice QSO Party!

The aim is to encourage as many Radio Amateurs as possible to learn about FreeDV and encourage as many FreeDV signals to be on the air as possible to help spread the word about this new mode.

If you can use WSJT-X for FT8 or any other digital modes software then, with the addition of Headphones and a microphone on your PC, you can switch to digital voice transmission in an instant! Its that easy! So why not give it a try? This is a great way to experiment with something new from the comfort of your own armchair. All it takes is a little bit of time to download, install and setup the software – nothing more!

What to know more? The QSO party rules are below, plus details of where to get FreeDV are included later in this bulletin. Read on!

The Rules

When: April 27th 0300z to April 28th 0300z 2019

Where: All HF Bands from 80m – 10m (excluding the WARC bands)

How: Work as many stations as possible using the FreeDV 700D or FreeDV 1600 modes in 24 hours.

Centre Frequencies: 1870kHz, 3630kHz, 7180kHz, 14130kHz, 21180kHz, 28330kHz (chosen in accordance with IARU Bandplans)

Points: Stations participating can earn points per QSO

  • 1 point per contact within a continent
  • 5 points per contact between continents
  • 50 points per contact with VK5ARG

(AREG’s club station is planned to be manned for the 24hrs looking particularly for inter-continental DX on 40/20 and 15m)


  • 1 per call area in VK/VE/JA/ZL per band +
  • 1 per DXCC entity per band +
  • 1 per inter-continental contact

Final Score:

  • Sum all points x sum all multipliers

You can work a station once per band.

Stations earning 50 points or more will be entitled to an emailed PDF certificate indicating their successful participation in this inaugural event!

What is FreeDV?

FreeDV is an open source digital voice transmission mode developed for HF Amateur Radio by David VK5DGR. It is founded on open source principles with the Codec2 specification and code fully available to the Amateur Radio community at no charge.

The latest development, FreeDV 700D mode has performance equivalent or better than SSB on HF – a remarkable achievement in only 700 bps!

Why FreeDV?

FreeDV 700D outperforms SSB at low SNRs – you can get an easy copy of 700D when SSB is unusable.

Amateur Radio is transitioning from analog to digital, much as it transitioned from AM to SSB in the 1950’s and 1960’s. How would you feel if one or two companies owned the patents for SSB, then forced you to use their technology, made it illegal to experiment with or even understand the technology, and insisted you stay locked to it for the next 100 years? That’s exactly what washappening with digital voice. But now, hams are in control of their technology again!

FreeDV is unique as it uses 100% Open Source Software, including the speech codec. No secrets, nothing proprietary! FreeDV represents a path for 21st century Amateur Radio where Hams are free to experiment and innovate, rather than a future locked into a single manufacturers closed technology.

FreeDV can be used on multiple platforms including Windows, Mac and Linux systems.

Where can I get FreeDV?

FreeDV software and more information is available from the FreeDV Website!

Supporting Events?

If you live in Adelaide, South Australia, there are two events planned prior to the QSO party to help you get FreeDV operational. AREG will be holding a “Tech Night” on April 5th at the clubrooms in the Fulham Community Centre starting 7.00pm. In addition, David VK5DGR (FreeDV’s creator) will be our guest presenter at the April AREG meeting on Friday the 12th. Doors open at 7.15pm for that event.

AREG is also looking to re-launch the FreeDV WIA News Broadcast. New times and frequencies will be announced soon! This provides a perfect opportunity to experiment with FreeDV reception while the broadcast is running for 30 minutes, plus you can participate in the callbacks afterwards.

At the April meeting a new version of FreeDV is also going to be released that promises significantly improved audio fidelity over the communications grade 700D and 1600 modes. Why not put it in your diary and come along – visitors are most welcome!

Want to know more?

Who can I Talk To?

Login to the K7VE FreeDV QSO Finder to find other Hams using FreeDV.


Please post your questions to the Digital Voice Google group

Developers please subscribe to the Codec 2 Mailing List.

IRC Chat

For casual chat there is a #freedv IRC channel on

We hope to see you on FreeDV!

Horus 52 – SHSSP 2019 Flight Report

This year AREG was once again involved with the International Space University’s Southern Hemisphere Space Studies Program (SHSSP), hosted by the University of South Australia. As with previous years, AREG performed a high-altitude balloon launch, carrying a SHSSP-developed payload. AREG members also worked with the project participants, running tutorials on various aspects of the launch.

The planned launch date was the 2nd of February, but had to be delayed a week due to poor flight-path predictions. In the lead-up to the new launch date (9th of February) predictions were looking good, however as the date got closer the prediction moved further and further north with a predicted landing to the west of Morgan. To make things even more interesting, the chance of showers at the launch site increased from 10%, to 30%, then to 70% over the final 3 days before the launch, along with predictions of 30kph winds.

Still, launch planning continued, and on the morning of Saturday the 9th of February the Project Horus launch crew and the SHSSP participants assembled at the Mt Barker High School oval for one of our most challenging launches to date!



After finding a filling location mostly out of the wind, the launch crew were able to get the balloon filled quickly and get the payloads laid out ready for launch. SHSSP participants assembled and tested their payload, before sealing it up ready for the launch.

Just as the planned launch time of 11AM approached, the launch director was informed by Air Traffic Control that a 10 minute launch hold was required. This couldn’t have come at a worse time, as the wind started to immediately pick up. The balloon wranglers had a very challenging time stopping the balloon from blowing around in the wind, with the latex envelope coming dangerously close to bursting many times.

Finally the launch was given the all-clear from ATC, and the payloads were released during in a short lull in the wind, using the classic ‘running launch’ method. Unlike a previous launch in high winds, the payloads easily cleared the trees and were on their way to the stratosphere.

A big thanks to all the launch crew for helping out – it was great to see many members at the launch site, and it certainly made this challenging launch a lot easier!

The Chase!

The chase teams for this flight consisted of Mark’s team (Mark VK5QI, Andy VK5AKH and Will VK5AHV), and Liam VK5LJG flying solo. As the flight path was predicted to be a long one (landing near Morgan!), the teams set of immediately after launch, leaving pack-up to the rest of the ground crew (thanks guys!).

Meanwhile tracking stations across the state began collecting telemetry. Michael VK5ZEA in Port Lincoln had his station in full swing:

While the AREG ground station deployed and manned by Peter VK5KX collected as much of the telemetry as possible from the multiple transmitters on this flight.

As for the chase and recovery teams, they steadily drove north through Palmer and Sedan heading for an expected landing near Morgan. The teams were caught by surprise by the balloon’s early burst at 25km altitude (the expected burst was 35km), which shifted the resulting landing prediction very close to the River Murray north-west of Waikerie.

Mark’s team immediately diverted through Blanchetown and headed towards landing area, and were able to track the payloads down to 62m altitude from the highway. A route to the landing site (in a vineyard at Qualco) was determined, and the team continued on. Unfortunately Liam VK5LJG had a vehicle fault, and had to stop at the Blanchetown roadhouse to await repairs.

Horus 52 Flight Path

While Mark’s team was approaching Waikerie, Steve VK5ST also made an appearance – he had been waiting near Morgan for the balloon to land, and had made his way to the landing area. After a brief discussion with the Vineyard manager the teams were able to drive right to the payloads, which had landed across four rows of ripe grapevines.

The SHSSP payload, suspended between grapevines.

Mark’s team then headed on to Waikerie for a much needed Bakery visit!

Tracking & Telemetry

As usual, we had a good showing of Amateur Radio operators from around the state receiving telemetry from the balloon. It was good to see a few new callsigns tracking telemetry (Hi Liam!) as well as our regulars.

The flight had the usual RTTY and 4FSK payloads, the telemetry statistics of which are shown below:

RTTY Payload

CallsignReceived PacketsPercentage of Flight ReceivedFirst-Received Altitude (m)Last-Received Altitude (m)

4FSK (Binary) Payload

CallsignReceived PacketsPercentage of Flight ReceivedFirst-Received Altitude (m)Last-Received Altitude (m)

Thanks to all who participated!

Wenet Imagery Payloads

This flight featured two Wenet imagery payloads – one with a downward-facing camera, and one outward-facing (for nice horizon photos). For the most part, these were identical to the Wenet payloads flown in previous Horus launches. The downward-facing payload was also configured to to receive telemetry from a SHSSP-designed payload and relay it to the ground via the Wenet FSK downlink.

Even though it was quite cloudy, the two payloads were able to capture excellent imagery throughout the flight.

Thanks to the following receiving stations who contributed to the Wenet reception effort:

Downward Facing Imagery

This slideshow requires JavaScript.

CallsignPackets ReceivedTotal Data Received (MiB)
VK5QI (Mobile)338708.27

Outward Facing Imagery

This slideshow requires JavaScript.

CallsignPackets ReceivedTotal Data Received (MiB)
VK5QI (Mobile)9776223.87

SHSSP Payload – Radiation Monitoring

This year, the SHSSP decided to develop a payload to measure ionising radiation throughout the balloon flight. The majority of ionising radiation observed in the troposphere and stratosphere are a result of cosmic rays interacting with particles of air, producing showers of secondary particles which can be observed using radiation sensors.

Two radiation sensor types were used: a geiger-muller tube, and a PIN-diode-based sensor. Radiation detection events were logged by a Raspberry Pi Zero W, and relayed to the downward-facing Wenet payload for transmission to the ground throughout the flight.

From the flight data, Bill Cowley (VK5DSP) was able to create plots of radiation count vs altitude:

These plots show the ‘Regener-Pfotzer Maximum’ at ~18km altitude the characteristic peak in the distribution of charged particles in the atmosphere. Above this point the radiation intensity drops due to there being less atmosphere for cosmic ray interactions to occur; below it, the intensity drops due to secondary particles being blocked by denser atmosphere.  A full writeup of the payload and results are over on Bill Cowley’s blog.


With the usual excellent imagery from the Wenet payloads, and the good data from the SHSSP payload, this flight can definitely be considered a success – even with the early burst. Thanks again to all who participated, and we look forward to more Project Horus flights in the future!

Horus 52 - Flight Statistics

Flight Designation:Horus 52 - SHSSP 2019
Launch Date:2019-02-09 00:40 UTC
Landing Date:2019-02-09 02:38 UTC
Flight Duration:1 Hour 58 Minutes
Launch Site:-35.07668,138.85643
Landing Site:34.12273,139.871
Distance Traveled:140 km
Maximum Altitude:25,497 m

Horus 52 / SHSSP 2019 – Frequency & Tracking Data

Horus 52 – Saturday 9th February 11.00am Liftoff!

AREG is pleased to once again be involved with the International Space University’s Southern Hemisphere Space Studies Program hosted by the University of South Australia. This year one balloon is being launched from Mt Barker High School as part of the program. All amateurs across the state are invited to participate in the flight through collecting the RTTY telemetry. All you need is an SSB receiver on 70cm, and an interface to your computer. The rest is software!

You can find out more about the software you need to track the balloon via our software tracking page

Telemetry Payloads

As always, we’ll be flying the usual assortment of telemetry payloads, including:

  • Our usual 100 baud 7N2 RTTY telemetry on 434.650 MHz USB. This can be decoded using dl-fldigi, with a reception guide available hereNOTE: There is a known issue with dl-fldigi where it does not upload any received telemetry until about 10 minutes after the software is started. Any telemetry received in this time period will be queued and uploaded after the startup period has completed (i.e. no telemetry will be lost).Note: Recent testing of dl-fldigi’s decode performance has found that the auto-configured RTTY receive bandwidth is too narrow, and can detrimentally impact decode performance (by up to 3dB!).To fix this, open dl-fldigi, and in the Configure menu, select Modems, and then go to the ‘RTTY’ tab. Drag the ‘Receive filter bandwidth’ slider to 200, then click ‘Save’. Note that this setting will be reset whenever you hit the ‘Auto-Configure’ button!
  • 4FSK Telemetry decoder

    The new 4FSK Binary telemetry will be transmitting on 434.640 MHz USB. This uses a separate decoder, with setup instructions for this available here. We would love reports of how the 4FSK signal compares to standard RTTY!


Wenet Imagery Payloads

This flight will feature two ‘Wenet’ high-speed imagery payloads, as have been flown on many previous Horus launches. The centre frequencies for the transmissions are:

  • 441.200 MHz – Nadir-pointing (Downward) Imagery
  • 443.500 MHz – Horizon-pointing Imagery

These will be downlinking HD pictures throughout the flight, which will be available at this link:

Reception of the Wenet signal requires a RTLSDR and a Linux PC/Laptop. Instructions on how to set up the required software are available here.

Note that users running an ‘older’ version (Circa mid-2018) of the Wenet receiver software will need to apply a -220kHz offset to the above frequencies in their file (i.e. 440980000 or 443280000) – or just leave them at their defaults, which should already be correct.. Those running the latest version can just define the centre frequency as-is. Older versions of the Wenet software will show a lot of ‘Unknown Packet Type’ messages due to some new telemetry formats we are trialling on this flight.

Online Tracking

Tracking of the flight will be available on the HabHub Tracker, available at this link. (Note that other balloon launches will also be visible on this page, including the Bureau of Meteorology launches from Adelaide Airport).
Follow the #SHSSP hashtag on Twitter for updates from the launch and chase teams on the launch day.

Flight Prediction

The following will give you an idea of the expected flight track for Saturday. It is going to be a LONG chase this time! See you all on Saturday!

Horus 52 – On track for Saturday 9th Feb Launch

AREG is once again involved with the University of South Australia’s Southern Hemisphere Space Studies Program this year, which is run by UniSA on behalf of the International Space University. The launch, which was scrubbed last week due to the predicted landing zone is now planned for this coming Saturday 9th Feburary, with liftoff planned for ~11AM. The weather is looking much better!

The current predictions look as follows:

Payload Plans

While some details are still to be worked out, it’s looking like the following payloads will be flying:

  • RTTY – 434.650 MHz
  • 4FSK – 434.640 MHz
  • Wenet – 441.200 MHz  (downward facing images)
  • Wenet #2 – 443.5 MHz (horizon-facing images)

There is still a chance the second Wenet payload will be dropped from the launch due to weight restrictions, so if you don’t see any signal on 443.5 MHz, that’s what’s happened!

As always, amateurs from across the state are encouraged to take part, by collecting the telemetry data and relaying it to HabHub on the Internet. This data is used to help fill in any missing data the chase teams fail to capture, which they can use to help maximize their landing zone prediction accuracy. In that way, everyone taking part is adding to the success of the mission.

Tracking details will be provided closer to the launch. Keep watching the AREG website for details!


UniSA: Southern Hemisphere Space Studies Program – Horus 52 – POSTPONED TO 9th FEB

AREG will be launching a high-altitude balloon for the International Space University’s South Hemisphere Space Studies program, conducted by the University of South Australia again this year. The planned launch date is Saturday the 2nd of February, with liftoff around 10-10:30AM. The launch site will be the usual Mt Barker High School Oval location.

UPDATE 2019-01-31: Due to poor launch-day weather, this launch has been re-scheduled to 11AM on Saturday the 9th of February.

Payload Plans

While some details are still to be worked out, it’s looking like the following payloads will be flying:

  • RTTY – 434.650 MHz
  • 4FSK – 434.640 MHz
  • Wenet – 441.200 MHz  (downward facing images)

There may be a second Wenet payload on 443.5 MHz capturing outward-facing imagery, though this is yet to be confirmed.

As always, amateurs from across the state are encouraged to take part, by collecting the telemetry data and relaying it to HabHub on the Internet. This data is used to help fill in any missing data the chase teams fail to capture, which they can use to help maximize their landing zone prediction accuracy. In that way, everyone taking part is adding to the success of the mission.


There have been some updates made to the Wenet HD imaging payload and receiver software, however all changes are backwards compatible. If you have a functioning Wenet receiver system, you *do not need to update for this launch*.

However, if you’re a bit more adventurous, the latest updates are on Github here:

You will likely need to wipe your existing Wenet directory and follow the setup instructions from the start.

Stay tuned for further updates as we get closer towards the launch date…

73  Mark VK5QI

Project Horus – Telemetry Test Flight #2 (Horus 51) Flight Report

Today’s telemetry test flight (now designated as Horus 51) was performed with (mostly) good results! This launch was an experiment to investigate solutions to the ‘Horus Binary’ payload PLL-loss-of-lock issue that has been observed on previous launches. Three payloads were launched, with variations on insulation and transmit power, all using reprogrammed Vaisala RS41 radiosonde PCBs. As a result, there was a lot of telemetry to receive on this flight!

Getting ready to launch the payloads

The launch was a fairly relaxed affair, with only a small launch crew on-site. Launch occurred right on time at 11AM. It was quickly discovered that a bit too much helium was used (dodgy gas flow-rate meter!), and so the ascent rate was higher than expected resulting in the small balloon used bursting at 16.2km altitude.

Horus 51 Flight Path

As the pre-launch flight path prediction had the landing area somewhere south-west of Loxton, none of the launch crew attempted to chase this launch. Instead, Ivan (VK5HS) from the Riverland Radio Club lead a small team (Ivan, David and Peter) out from Renmark to recover the payload. As it turns out, the higher ascent rate and lower burst altitude resulted in the landing location being further away from Loxton than expected, but the Riverland boys were able to track payloads down to the ground and easily recover them not long after landing.

David (left) and Peter (right) with the recovered payloads.

Many thanks to Ivan & Co for making the effort to get out and chase, it is much appreciated!

Horus 51 - Flight Statistics

Flight Designation:Horus 51 - Telemetry Test Flight #2
Launch Date:2018-11-25 00:30 UTC
Landing Date:2018-11-25 01:40 UTC
Flight Duration:1 Hour 10 Minutes
Launch Site:-35.07568, 138.85701
Landing Site:-34.68642,139.92380
Distance Traveled:106 km
Maximum Altitude:16,201 m

Telemetry Statistics

Thanks to all who participated in the launch by receiving telemetry from one (or more!) of the three payloads. Statistics on how much telemetry was contributed by each receiver callsign is below:

Horus 51 - HORUSBINARY (434.640 MHz) Receiver Statistics

CallsignReceived PacketsPercentage of Flight ReceivedFirst-Received Altitude (m)Last-Received Altitude (m)

Horus 51 - HORUSBINARY2 (434.650 MHz) Receiver Statistics

CallsignReceived PacketsPercentage of Flight ReceivedFirst-Received Altitude (m)Last-Received Altitude (m)

Horus 51 - 4FSKTEST (434.660 MHz) Receiver Statistics

CallsignReceived PacketsPercentage of Flight ReceivedFirst-Received Altitude (m)Last-Received Altitude (m)

Please make sure you follow the configuration instructions when using the Horus Binary decoder, to avoid the ‘YOUR_CALL_HERE’ entries seen in the above tables!

Payload Testing Results

Previous Horus launches have seen the repurposed Vaisala RS41 payloads lose PLL-lock mid-flight, with the transmit frequency drifting up the 70cm band as temperature decreases. Testing on the ground indicated this may be due to the Radio IC (a Silicon Laboratories Si4032 FSK transmitter) failing with the low temperatures experienced during flight. The fact that the the RS41 sondes do not usually fail during their intended application pointed at the lower transmit power (25mW vs 50mW) used on Horus flights being a possible factor.

On previous flights the following results were seen:

  • Horus 49 (Anstey 2.0) – RS41 Foam Only, 25mW – No issues Encountered.
  • Telemetry Test Flight #1 – RS41 Foam Only, 25mw – Failed on Ascent at 9km altitude, recovered on descent at 1km altitude.
  • Horus 50 – Stock RS41, 25mW – Failed on descent for ~6 minutes between 13km and 9km altitude.

With 2 failures and one success, it was decided that more data needed to be gathered.

Foam-Only (Left), ‘Stock’ RS41 (Middle), Custom Enclosure (Right)

On this launch, two payloads were operated at 50mW transmit power, one with a ‘stock’ enclosure (‘HORUSBINARY’) and one with only the inner foam insulation (‘HORUSBINARY2’). Using only the inner foam insulation provides a significant weight reduction, cutting the payload weight almost in half (~120g to ~60g).

A third payload (‘4FSKTEST’), using a custom-built foam enclosure was also tested, transmitting at 25mW. This had a similar overall weight (66g) to the foam-only RS41 enclosure, and re-flew the RS41 board that failed on Horus 50.

A bug in the firmware, discovered after the Horus 50 flight, was also fixed for this launch. This fix allowed gathering of measurements from a temperature sensor on the silicon die of the radio transmitter IC – unfortunately the temperature measurements captured on previous launches are invalidated as a result of this bug.

Horus 51 Payload Temperatures

Sadly, the foam-only payload (‘HORUSBINARY2’) was observed to fail at 14.3km altitude during ascent, and recover at 4.8km on descent, failing with a radio IC temperature of 0 ˚C.

Failure of the HORUSBINARY2 payload, as observed by Joe VK5EI

Both the stock RS41 and custom enclosure payload remained operational throughout the flight. The overall higher temperatures reported by the Stock RS41 payload may be a result of a bias in the temperature sensor, or may be a result of the better insulation – Further investigation will be performed once the payloads make their way back to Adelaide.

Curiously, the two other payloads reported radio IC temperatures lower than the failure point of the foam-only payload (0˚C), indicating that perhaps it is not the radio IC at fault, but another component on the PCB. Further investigation will be performed on RS41 PCBs using selective cooling of components, prior to the next Horus launch sometime in January 2019.

However, based on the results from this flight, it appears that the safest option for the moment is the Stock RS41 enclosure, transmitting at 50mW. As always, Horus flights use  redundant telemetry transmitters, so that a failure of a single transmitter does not compromise our ability to track and recover!

Project Horus – Telemetry Test Flight #2 – Sunday 25th November 11AM CDST

UPDATE: Predictions look good, so this flight will be going ahead as planned. The launch team will not be chasing this flight – others are welcome to chase/recover the payloads if they wish.

Current planned flight parameters (for prediction purposes) are a 4m/s ascent rate, 20km burst altitude, and a ~7m/s descent rate.


On Sunday, the 25th of November, Project Horus will be performing a small balloon launch from Mt Barker High School Oval, at approximately 11AM CDST. Live flight tracking will be available on the HabHub online tracker as usual. A guide on how to decode the new Horus binary telemetry mode is available here.

This launch is another test flight of the new ‘Horus Binary’ telemetry payload, which uses a new modulation mode developed by David Rowe VK5DGR and Mark Jessop VK5QI with 6dB better performance than the usual RTTY telemetry. This telemetry mode has been flown on a few recent Project Horus flights, with mixed success – The modem has performed flawlessly, the payloads themselves not so much! These flights have flown reprogrammed Vaisala RS41 radiosondes, which while working perfectly on Bureau of Meteorology launches, have proven troublesome on Horus launches!

Drifty Horus Binary Payload – Hopefully not on this this flight!

The last telemetry test flight suffered a loss of PLL lock on ascent, believed to be due to temperature issues, causing the payload to drift right up the 70cm band. On Horus 50, a similar fault occurred on descent, though the payload recovered within a few minutes. Further investigations confirmed a temperature issue, likely due to the lower transmit powers used on Horus flights (25mW) compared with the stock transmit power of 50mW.

This flight aims to test a few different variations on the payload flown on Horus 50, to determine if transmitting at a higher power keeps the payload alive. A few different modifications to the payload insulation will also be tested.

Currently we plan to fly 3 telemetry payloads (all on USB, +/- temperature drift):

  • 434.640 MHz – Callsign ‘HORUSBINARY’ – Unmodified RS41, 50mW TX power.
  • 434.650 MHz – Callsign ‘HORUSBINARY2’ – RS41 without outer plastic shell, 50mW TX power. Prioritise reception of this payload.
  • 434.660 MHz – Callsign ‘4FSKTEST’ – RS41 PCB in custom enclosure, 25mW TX power.

The Horus Binary uploader script will automatically determine the payload callsign as long as you are running a recent version. Please make sure you have updated to the latest version (2018-11-15) of the Horus Binary uploader before this flight, otherwise the HORUSBINARY2 payload will not be recognised, and data for the other payloads may be corrupted. Those who were set up for Horus 50 can simply download the latest payload ID list, and place it in their horusbinary directory.

Launch will be from the usual Mt Barker High School Oval site, and launch teams will be on-site around 10:15AM, for a 11AM launch. All are welcome!

AREG 20th Anniversary – Horus 50 Flight Report


The Amateur Radio Experimenters Group was formed in July 1998 with the aim of promoting experimentation and self learning using Amateur Radio. 20 years on, the group is a vibrant and active body that has brought together people from many walks of life, all with the common interest of experimenting and learning about radio and electronics.

One of the founding project ideas conceived by Adrian VK5ZBR, Ben VK5BB and Rod VK5UDX that drove the creation of AREG was project “Skyhook“. The aim, back then, was to fly an amateur radio payload under a weather balloon. For various reasons that goal was never achieved. However, through Project Horus (which joined AREG several years ago under the then stewardship of Terry VK5VZI), that original dream became a reality.

The view from Horus 50 – River Murray in the foreground with Adelaide in the top left of shot

This flight marks Project Horus’s own milestone, having now launched 50 “heavy – 30km plus” balloons over 8 years. In that time it has become one of the most active amateur high altitude balloon projects in Australia.

To commemorate both the 50th flight and the 20th anniversary, AREG and Project Horus have decided to fly an all Amateur Radio oriented payload, promoting our core experimentation theme. The aim was to maximise involvement of the amateur radio community in the project. Here is the story of that flight.

Horus 50 – Launch Preparations

The launch crew arrived on site at Mt Barker High School by 8.30am ready to prepare the payloads and the balloon. Mark VK5QI who was flight lead was assisted by a number of AREG members including Will VK5AHV, Andrew VK5AKH, Theo VK5IR (first time Horus hunter), Kim VK5FJ, Marcus VK5WTF, Oly VK5XDX, John VK5BJE and Grant VK5GR with a number of other visitors and members who came along to watch as well. Assembly of the balloon train went to plan and, with relatively calm conditions prevailing, the filling of the balloon went smoothly too.


After the obligatory calls to Air Traffic Control, the team was set and the balloon took to the skies on schedule at 10.00am ACDT.

Ground Tracking & Control Stations

In support of the flight, another AREG team had set up camp approximately 50km away at Bear Rock Lookout, up above Palmer on the eastern edge of the Mt Lofty ranges. Manned by Peter VK5KX and Matthew VK5ZM, this ground station provides a vital backup telemetry link, gathering all of the signals from all of the payloads and uplinking them to the internet for the chase teams to use.

This data, when mixed with the rest of the information being received by amateurs across the state, is used by the chase teams to help fill in any packets they miss from the balloon, improving the accuracy of their landing predictions and providing a safeguard for the landing positioning data.

Meanwhile the second ground team, consisting of Grant VK5GR and Oly VK5XDX, went to the top of the ranges above Brukunga to establish VK5ARG net control for this flight’s voice repeater. We weren’t able to collocate these teams as the UHF high power up-link would have overwhelmed the tracking data down-links.

The Chase Teams

Once the balloon took off, the Mt Barker based chase teams packed up the launch site and prepared to head out. Meanwhile Darin VK5IX also started the chase, in his case also from the Bear Rock lookout. There were a few new chase teams this time which was great to see! The teams were:

  • Mark VK5QI: Mark VK5QI, Will VK5AHV, Theo VK5MTM (his first Horus chase)
  • Liam VK5LJG: (Just Liam, his first Horus launch, though not his first balloon chase)
  • Kim VK5FJ: (Just Kim in the car)
  • Marcus VK5WTF: Marcus and family
  • Darin VK5IX: Darin, Glenys, Cam, Greg.

It was great to see more people getting out chasing!


Tracking and Telemetry Data Processing

There were many ways to track the flight. The usual balloon telemetry collection site was in full swing at where all four payloads were being tracked. Amateur Radio operators and the general public could also track this flight via the Amateur Position Reporting System (APRS) on websites like

APRS Tracking from tracking and telemety hub

The other very important aspect of the flights is the data collected by the distributed listener network of amateur radio enthusiasts spread across the state. This adds a huge level of reliability and redundancy to the system that the project team really appreciates. It also gives everyone an opportunity to contribute to the project, even if only from their own radio shacks.

The interest in this flight was very high and there were many first time listeners as well as many regulars tune in and gather the telemetry off one of the RTTY or 4FSK payloads, as well as through the APRS Internet Gateway network.

In all of these a special mention goes to Andrew VK3BQ who takes the prize for the most distant telemetry decoding station at over 600km away in Melbourne.

Here are the results of how much telemetry each station was able to contribute (Note – This is per-callsign used when uploading, so some stations may have duplicate entries):

100 Baud RTTY Beacon 434.650

CallsignPackets Received% of Flight Received

4FSK Binary Beacon 434.640

CallsignPackets Received% of Flight Received

A huge thank you to everyone who collected the telemetry!

This telemetry stream also allows us to analyse the path the balloon took and to confirm the flight’s vital statistics:

Not all plain sailing for the telemetry

The flight was not without it’s gremlins either. The 4FSK binary telemetry payload, which was a recovered Vaisala RS41 Radiosonde that has been re-programmed for use on 70cm, lost PLL lock at 13km on descent, and regained it at 9km altitude (about 6 minutes later). The air temperature at 13km was <-60 degrees C according to the morning BOM radiosonde launch, and -40 degrees C at 9km. The team suspects that the payload froze for a period due to it running lower power than it would for a normal sonde launch, thus not generating enough internal heat to keep from freezing. It is hoped to test this out sometime in the towards the end of the month with a small test launch carrying the same payload but running 3dB more TX power along side another RS41 PCB in a custom foam box (similar to our RTTY payload boxes).

The LoRa tele-command payload also had a fault where it lost GPS lock for the second half of the flight just after burst, likely due to it getting knocked around due to the huge dynamic shock that ripples through the payloads when the balloon bursts. This time, the GPS unit took 20 minutes to regain lock, probably because it was falling so fast (~20-60m/s). The team will be investigating some better AA battery holders, and possibly putting a big capacitor across the power input to hold up the GPS through that very dynamic part of the flight.

It goes to show, every flight is an experiment and that the team learns something new every flight!

Payloads – Slow Scan TV

The main attractions of this flight, of course, was the flying voice repeater and the first flight of the Slow Scan TV transmitter.

The live pictures broadcast over Slow Scan TV were a spectacular success, with amateurs across VK5 and VK3 able to receive them using all manner of tools and systems. The SSTV signal, running 250mW used what is known as Scottie 2 format (commonly used on HF).  For the first time these images were accessible to almost everyone without any special software (which the previous high definition Wenet SSDV picture system does require). This helped generated an unprecedented interest in the flight.

We had clubs and individuals from the Riverland, South Coast, across Adelaide, and in one case from as far away as Melbourne all receiving the SSTV transmitter.

Rick Kearsley (from the South Coast ARC) received SSTV images from Horus 50 from Normanville SA with  by VK5LEX/P and VK5VCR/P.

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In the Riverland, Peter VK5PE and Ivan VK5HS joined in the fun.

AREG also received copies of the pictures received by Steve VK5SFA and Liam VK5LJG and know of several others in Adelaide who also successfully received the images live from the balloon (including our primary ground station at VK5KX/P, who received one only 500ft off the ground).

Last SSTV Image before landing captured by VK5KX

The best effort award however must go to Alan, VK3DXE who from the eastern side of Melbourne was able to receive the SSTV transmitter at apogee using his EME station. Not a bad effort for a 250mW FM transmission on 145.1MHz at over 630km range.

VK3DXE Receiving Horus 50 SSTV from Melbourne over 600km away

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This was the array Alan was using.

Photo thanks to VK3DXE

From the balloon’s perspective we also kept a copy of the images on the SD card. This is what they looked like prior to broadcast.

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Payloads – Voice Repeater

The other amateur radio related payload flown was a cross band voice repeater. This machine had a receiver on 438.900MHz (with a 123Hz CTCSS tone) and a transmitter on 147.500MHz running approximately 1 Watt. This was a return to the original voice repeater flown back on Horus 9 and 23 after the problems with narrow band FM on the more recent repeater flights.

During the flight, it became clear that this old machine still had some problems. Unfortunately the faults didn’t reveal themselves until after lift off. The repeater was de-sensitising its own receiver (a suspected 3rd harmonic problem), and with the rather windy flight aloft, there was also a lot of swinging around of the antennas (TV Ribbon J-Pole antennas) which made contact very difficult to achieve through the balloon. None the less, 32 contacts were logged through the repeater by stations from as far as Millicent in the SE, Renmark in the NE and Whyalla / Port Pirie in the Iron Triangle to the NW.

Contact Map (created using

The following is the full log of the contacts made through the balloon with net control.


VK5IR2018-11-032341Z147.5FMMansfield Park
VK5WTF2018-11-032344Z147.5FMMunno Para
VK5APR2018-11-032345Z147.5FMFlinders Park
VK5KX2018-11-032345Z147.5FMSalisbury Park
VK5BB2018-11-032351Z147.5FMRedwood Park
VK5YX2018-11-032356Z147.5FMHallett Cove
VK5DMC2018-11-040023Z147.5FMPort Pirie
VK5ALX2018-11-040024Z147.5FMWhyalla Playford
VK5WU2018-11-040108Z147.5FMHope Valley
VK5KBJ2018-11-040126Z147.5FMAldinga Beach
VK5JP2018-11-040142Z147.5FMNorth Haven

Payload Recovery

As sure as the laws of gravity go, what goes up must come down! The balloon climbed to over 35km before bursting and returning to earth. The following are the vital statistics of this flight:

Flight Designation:Horus 50 - AREG 20th Birthday
Launch Date:2018-10-03 23:14 UTC
Landing Date:2018-10-04 01:59 UTC
Flight Duration:2 Hours 45 Minutes
Launch Site:-35.07568, 138.85701
Landing Site:-35.184284, 139.755216
Distance Traveled:82.6 km
Maximum Altitude:35,861 m

The chase teams themselves were in an excellent position to recover the payloads and indeed watched them land from about 1km away. After contacting the land owner (to seek permission to enter and collect them), all of the payloads were successfully recovered, ready to fly another day.

Recovery Team – L-R VK5IR, VK5LJG, Greg, Cam, VK5WTF, VK5IX, VK5AHV, VK5QI


At the end of the day the team was very happy with the results. What was even better were the number of people who participated in the event, either on site or from home with tracking, SSTV, FM voice, or just tuning in on social media and following along via the Internet. It truly represents the aims of AREG in promoting experimentation in Amateur Radio to see all of the people who joined in. To each and everyone of you, thank you for your participating!

To the teams that built and flew the balloon, a special thank you to you as well. May there be many more!

73 de Grant VK5GR