Announcement - launching Friday 8 May (Ichthus)

[Steven Boonstoppel]

Hi folks,

Unless a major shift in the forecast occurs, I am launching a balloon this Friday!

Time: aiming for 9AM CEST = 8AM BST = 7AM GMT.

Location: grass field below Ichthus College, Veenendaal, Netherlands (52.026438406839766, 5.526726020499952) (https://xkcd.com/2170/)

Balloon: HY-50 with 0.35m³ helium, expecting an altitude of slightly over or under 20km.

Payload: XIAO SAMD21, Ra-02, ATGM336H and probably a BME280 or so.

Parachute: designed and made by students

(should be slightly under 100g for payload and parachute combined)

LoRa: mode 2 on 432.662 MHz

Horus: v3 on 434.713 MHz and 437.600 MHz

Chasing it myself with a T-Beam for LoRa and laptop for HorusBinary.

Let's see if we can get some hits across the borders/Channel again :)

Cheers,

Steven

[Patrick van Staveren]

+1 for the classic XKCD reference!

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[Nick McCloud]

On Tuesday, 5 May 2026 at 19:15:00 UTC+1 Steven Boonstoppel wrote:

expecting an altitude of slightly over or under 20km.

https://xkcd.com/2205/

 

 

Horus: v3 on 434.713 MHz and 437.600 MHz

Any pointers on your SDR settings to maximise reliable reception? 

[Steven Boonstoppel]

So I checked some screenshots and last time I had a SNR just shy of 0 while they were both on the desk. But then I had no clue what I should be looking for in SDR++ and I just had it configured for the frequency that I used in Settings.h and it was looking like this:

Notice that I was already conferring with Nick back then about the poor reception... and that I set it to 434.714MHz (device transmitting on 434.713MHz) because I was informed to slightly shift the frequency around to see if that improved the decoding. But my axis was waayyy too wide (see the 2.4MHz in the top left) so I had no clue what I was aiming for and how (much) I should be shifting. I had a message "HorusBinary OFFLINE" from Nick before I could even walk to the car on the other side of the tiny football field after releasing the balloon. Oh, and HorusGUI was set to 270Hz tone spacing while I'm using an SX1276 which doesn't do 270 but 244.

So now I select the smallest value in the top left (250kHz) AND I zoom in using the controls in the top right and you very clearly see the signal and its sidebands:

The white stripe in the middle is the portion of the signal that is actually being passed on as audio to HorusGUI (the bandwidth is configured bottom left in the second screenshot) and it should be centered perfectly on the strongest middle signal. And I configured HorusGUI for 244Hz tonespacing.

With this I get a consistent SNR between 16 and 20 on the desk!

Note that I have terrible results with Webhorus: it fails to decode pretty much any packet. But don't need that now so not investigating further at this point.

Op wo 6 mei 2026 om 00:14 schreef Nick McCloud <nick.at....@gmail.com>:

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[Ross G6GVI]

I wonder if there's a lower setting for "Sample Rate" in your SDR menus? If you're using the 2MHz default for the RTL dongle, that will be showing a much wider span than you need (and using up more processor resource than necessary).

Just 480 or 240kHz should be fine for a narrowband signal such as 4FSK.

[Mark Jessop]

If you're having issues running at a RTLSDR at even 2 MHz, then the machine is likely too underpowered for this kind of work...

73

Mark VK5QI

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[Steven Boonstoppel]

As I said I now use 250kHz (the lowest available option for me in SDR++).

My laptop has no trouble handling multiples of MHz :)

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[Ben Z en de rest]

Someone notices and mentioned the RF gain is set to zero in the SDRPP screenshot ?

Op do 7 mei 2026 om 15:12 schreef Steven Boonstoppel <steven.bo...@gmail.com>:

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[Nick McCloud]

I'll leave details to Steven to report, but payload landed in a field with a small wood shielding the in-car LoRa tracker from reception so a little bit of walking was required. 

So all good and thanks to all those receiving.

[Steven Boonstoppel]

Let me start of repeating Nick's message: thanks everyone that tuned in (or already had a radio running)!

Launch was all good - here's me adjusting the antenna right before take-off as photographed by my father who came along:

We counted down with the students as one of them released the string from the cylinder and off she went. 

The initial ascent rate was a little slower than hoped at 3.0 m/s but it slowly picked up more speed and got up to and over 4 m/s at high(er) altitude. As the chase car was faster than the balloon we visited the sheep shed on our way, and halted at a church that could fit the whole of the village it was located at while waiting for the burst to happen. We beat last time's altitude as it last reported 21,650m before burst!

As the predicted time to landing was roughly 35 minutes and the drive was 25 minutes we peeked inside the church before starting the actual chase. We were on track to catch its landing - see picture:

But these tracking points at 800m altitude were the last ones received, likely because of the row of pretty (and) tall trees between the car and the balloon. So we abandoned the car, swapped the magmount antenna on the mobile LoRa receiver for a normal quarter-wavelength and headed to the predicted landing site. We didn't pick up any signal, which was relieving because that meant it likely wasn't in one of the trees. Since the parachute last time landed a couple hundred meters before the Sondehub prediction we decided to traverse the strip of trees and bushes just before the predicted crash, and lo and behold, while jumping over a small trench, we picked up the signal from the grass meadow ahead. Que the ladies sprinting ahead  - the best parachute was crafted by a group of four girls - and we cheered happily as everything was intact and picked up off the ground: https://photos.app.goo.gl/mTRn5tYtoGos9J4D8

After driving home for an hour, we arrived back at school one minute after the bell rang for their normal end of school day.

The payload used a BME280 internally and BME680 externally - the external temperature reported -53.6C at its coldest with the internal temperature reporting roughly 20 degrees higher for most of the flight and -36.4C at its coldest. At burst, the reported pressure was just 41.4hPa!

Grafana dashboard link.

Op vr 8 mei 2026 om 11:55 schreef Nick McCloud <nick.at....@gmail.com>:

I'll leave details to Steven to report, but payload landed in a field with a small wood shielding the in-car LoRa tracker from reception so a little bit of walking was required. 

So all good and thanks to all those receiving.

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[John Laidler]

Well done to all those involved and a good altitude achieved. 

John

M0WIV 

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[Nick McCloud]

On Friday, 8 May 2026 at 13:58:06 UTC+1 John Laidler wrote:

 a good altitude achieved. 

More luck than judgement - I managed to trick Steven in to testing the 50g balloon and then you used one and now we have another data point.

As both of Steven's uses a whole canister of 50 x 9" party helium, I can start trying to back calculate the figures to go in to a burst calculator of some sorts somewhere.

[John Laidler]

Nick,

A burst calculator for the HW-50  would be very valuable.  I'm hoping to launch another in August or September so that may provide another data point. If conditions are suitable I may try for a slow ascent to see how high it can go. But after the last launch conditions will need to be good so I don't have to drive too far!

John 

M0WIV 

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[Nick McCloud]

On Friday, 8 May 2026 at 17:22:24 UTC+1 John Laidler wrote:

I'm hoping to launch another in August or September so that may provide another data point. If conditions are suitable I may try for a slow ascent to see how high it can go. 

To be of immediate use as a data point for the project I'm working on you can ONLY use a complete 50 x 9" party Helium cylinder and ideally a 100g payload or close enough. Once we have a working solution for that volume of gas with that sort of weight of payload, then it can be tested against variations. The scheme I devised with Steven is to make the fill stupid-easy in a school environment - no bottles of water hanging off the bottom in gusty conditions making the float hard to detect - plus easy to get the materials that are easy to risk-assess (no heavy cylinders etc) that includes a custom parachute size using a stout plastic bag.

If you use a different volume &/or different payload weight it will help, but won't be so easy to fit in initially.

Fingers crossed I'll get the opportunity to fly a couple of these micro-HABs in the meanwhile, then we can hack together something for your plans to test variations.

[John Laidler]

Nick,

I understand the reasoning now, you need to know the volume of gas used. I'll factor that in.

John 

M0WIV 

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