High tech falling out of the sky?
Is this true?
Yes, 3000 times each day around the world.
And it can be a lot of fun to hunt this “fall-out.”
With a LoRa module, a Raspberry Pi, and an RTL-SDR dongle.
Come with me on a drive through the night.
And learn how you can experience such adventures, too.
Maybe with your kids?
Grüezi YouTubers.
Here is the guy with the Swiss accent.
With a new episode and fresh ideas around sensors and microcontrollers.
Remember: If you subscribe, you will always sit in the first row.
Starting weather balloons with some radio equipment is cool.
For example, to produce world record distances with LoRa.
The effort for such a launch is high and the cost, too.
What if the government would sponsor these launches?
Would that be cool?
This is precisely what happens.
According to Wikipedia, there are around 1300 launch sites, and they launch balloons at
least at 11 and 23 UTC.
So every day around 3000 balloons to chase.
Cool.
And here you see them flying all over Europe!
So in this video, we will cover things like: - What do these balloons measure, and how
do they work?
- What technologies do they use?
All nice.
But more interesting: We will hunt them.
I will show you how to build a simple tracker to search for them and a ”surveillance station”
for longtime monitoring if you are interested.
Let’s start this exciting journey.
And together, we will go on a hunt or two.
When I got this message from Peter, one of my viewers, that a weather balloon will soon
fall on my head, I remembered that chasing those weather balloons was for a long time
on my bucket list.
Now it was the time to start the project.
Balloons are used for atmospheric “sounding.”
They profile temperature, humidity, wind speed and direction, and other parameters.
The data is used for weather forecasting.
Their measurements are transmitted over the air and, therefore, can be heard by everybody.
Two frequency ranges are used: around 403 and 1680MHz.
I will concentrate on the 403 band used around here and leave you a link for the US viewers.
In the US, there are also nearly 100 launch sites.
Unfortunately, it seems to be a little less comfortable to hunt balloons in the US.
But maybe this video will trigger some actions to make it simpler there, too.
The same applies to Australia, where they also have plenty of launch sites.
A few other things a “hunter” has to know: The balloons are made of latex and are filled
with hydrogen or helium.
They climb relatively fast and usually burst at above 30’000 meters.
Then they start to descend on a parachute and still travel a long distance till they
land somewhere.
If we want to find them, we need two essential things:
1.
A prediction if a balloon is heading in our direction and when it will be launched
2.
A receiver to decode the signal, especially its position.
The closer we know the position of the landing, the easier we will find it.
And we can decide if it is worthwhile even to start a recovery attempt as we will later
see Let’s start with the first point.
To make a prediction, we need a list of all balloon launch facilities around our home
or our holiday location.
Balloons can travel 100 km and more.
For these 120 launch sites, it is easy to get predictions: Radiosondy.info assembles
all needed information around past, current, and future flights, including the type of
the sonde and its frequency.
And it maps the data on Open Street Map.
Here you see all covered launches for the next few hours, for example.
If I zoom in, I see that I have a chance to get balloons from maybe four launch sites.
The closest, Payerne, is less than 100 km away.
As we see in Peter’s message, three balloons have the potential to land in my area.
The rest is going in other directions, and I do not want to drive too far.
The first launch will be at midnight today.
So I have to hurry up to build the rest of the needed infrastructure.
In the old days, they were not able to decode the messages.
So they used a portable receiver and a directional antenna to triangulate and find the balloon.
This was not easy, especially at night.
And because the radiosonde battery is not too big, it only emits a signal for a few
hours.
Today it is much easier because we can decode the signal and use the built-in GPS of the
radiosonde.
If we have a receiver for the Gaussian Frequency Shift, short GFSK, modulated packets sent
around 403MHz, and decoding software, we always know where the balloon is.
At least as long as we can receive its signal.
Easy.
The frequency is very close to 433MHz, and our LoRa chips can also receive GFSK.
So we only need software to do so.
And such software exists: Its name is MySondy Go, programmed by two Italians.
We only have to flash a bin file to a 433MHz TTGO LoRa board, and ready is the receiver
for weather balloon data.
No big antenna, no SDR receiver.
Just a TTGO LoRa board with a display.
And there is even a companion app for Android Smartphones, which displays our and the balloon's
position.
After an hour or so, I had my balloon tracker prototype connected to a power bank.
I am sure this will be very useful in future hunts.
Let’s check it out.
It is already after midnight, and the balloon in Payerne should already be in the air.
Right from outside my house, I hear the balloon on 403.5MHz using a general-purpose Baofeng.
And my freshly built balloon tracker also blinks the green LED, the sign for a reception.
It displays the number of the radiosonde and its position.
And the Smartphone app shows its position in open Street Maps.
Super!
In the beginning, the balloon follows its predicted path.
But suddenly, it changes its direction.
On radiosondy.info we can follow its track, and a real-time simulation determines its
landing point.
It becomes more and more apparent that it will land in less than 10 km distance from
me.
It is now after 1 AM, and I cannot resist: I have to find it.
Short check: What do I need?
My new tracker, including the power bank, the Smartphone, light, and, very important,
rubber boots because it most probably will not land on the road.
So I drive into the night.
In the meantime, Peter reported over WhatsApp that the balloon landed in a gravel pit in
Germany.
A network of surveillance stations was able to track it nearly till its landing.
So it should be easy to locate.
But, gravel pits are private ground.
Around one kilometer from the predicted touchdown point, my tracker started to blink, a sign
it got the real position directly from the radiosonde.
Very good.
And really, as predicted by radiosondy.info, it should be at the end of the gravel pit
on the other side of the railroad.
Hopefully, no train will pass at this night time.
Do you remember the rubber boots?
Now I mount them because it was raining the whole day.
And I tried to get to the balloon.
You see, it was very dark!
Unfortunately, the direct way was not the best, and a high fence made it impossible
to enter.
I was just a few meters away and had to return to my car.
But longtime subscribers know that I do not give up, even in the middle of the night!
I tried it from another position, and here, after searching, I found a small hole in the
fence.
Big enough to enter.
Now I was in, and after a short walk, the balloon appeared in front of me.
It was easy to recognize because it was more or less intact.
I remembered that it only reached about 17’200 meters.
So it did not burst as usual.
The balloon, BTW, is perfect for latex lovers.
It smells exactly like that.
But, as a nerd, latex is not my interest; I wanted the radiosonde.
There is a long cord between the balloon and the sonde.
So it should be easy to find.
And really: I found it, but, with all this excitement, forgot to press the record button
on my smartphone.
BTW: You have to take a Swiss Army knife to cut the cord off with you.
I learned this the hard way one night later.
Now I can start my return.
Hopefully, I will find the hole in the fence and my car.
Fortunately, everything went well, and I arrived in our garage at nearly 4 AM.
So I had beginner’s luck on this successful first mission!
A short sleep followed.
Because the next balloon was predicted to land close to me, too, I wanted to finish
the second part of the project: My own surveillance station for weather balloons.
There are many such private stations connected to the radiosondy project.
But none close to where I live.
So mine would come in handy if the next balloon lands in my vicinity because it would provide
data close to the landing position.
A surveillance station consists of these parts: - A Raspberry Pi
- An RTL-SDR dongle - An antenna
- And some software This station should automatically receive
data from nearby weather balloons and send it to the radiosondy.info page.
If you register on radiosondy.info and fill in some information, an image is generated
for you to download and burn using Raspberry Pi imager.
BTW: You can attach up to 3 SDR sticks if you want to cover the whole frequency range.
Because I only want to cover radiosondes from Payerne, I start with one stick.
And I use an old Pi3 Model A. Mainly because I have it lying around.
And it has a small footprint.
I did not try a Pi Zero because I do not like its limitations.
Maybe it would work, too.
After flashing the image, you can connect to the Pi using the VNC viewer on another
PC.
The only thing left is to calibrate your SDR receiver.
It uses nearby 900MHz GSM stations to do so.
Innovative idea!
Use what you do not have to pay for.
Now my surveillance station is ready, too.
Right before the start of the next balloon.
Now we have time to look at the radiosonde.
Here we see a sensor and here the antenna.
Let’s start with the outside sensor: It is absolute high tech because it has to withstand
extreme conditions.
At 30’000 meters, in the rain and fog.
If we look at this particular sonde’s specification, we see that it uses a very precise platinum
resistor, which works up to -95 degrees Celsius.
The humidity sensor is a thin film capacitor.
So we can assume that there is a lot of know-how in this small sensor plate.
But what is inside the Styrofoam box?
If we open it, we see a dual-sided PCB with lots of vias for a proper ground connection.
The sensor, as well as the antenna, are connected to this PCB.
On the other side, we see two AA lithium batteries.
I assume they are used because they are lighter than standard AA batteries and have a working
temperature down to -40 degrees Celsius.
Which is not enough for the -50 degrees at 30’000 meters.
This is probably why they use Styrofoam for insulation.
This RS41-SG sonde does not have a pressure sensor populated.
It seems to use the u-blox GPS chip for altitude measurement.
As I showed in video #22, this measurement is not exact.
That is why sometimes it reports descending rates during the climb.
Of course, this GPS chip also determines the location of the sonde and so eases our search.
The CPU is a standard STM32F100 chip.
This enabled some projects to hack these sondes.
So you can change its frequency to the 433 MHz range where you can use it for your own
weather balloon.
I leave a link to some “hacker projects.”
You do not need to solder.
This connector, which is probably used by the launchers to store the number and the
frequency, is also a programming interface.
The radio chip is a “bread and butter” transmitter chip which outputs up to 20dBm
or 100 mW.
After my first success, I tasted blood.
The next balloon also was forecasted to land in my direction.
It landed short, and it was quite clear that its touchdown was in a forest.
But you never know, and I started the hunt again.
Now with the support of my newly built Raspbi, which already contributed its data to the
community.
I also printed a small case for my “tracker” and a battery.
Very handy!
And neat.
Because the balloon’s touchpoint was on a mountain, its signals were still received
by the network after landing, and I knew its exact position even without my tracker.
As you see, the weather was terrible, the hill extremely steep, and in the end, I discovered
what I already knew: I was standing precisely below the balloon but not see it because it
was high up in one of those trees.
This time, I had to go back without a trophy.
This is why I tried it a third time, also during the night.
And I was successful again.
The balloon was on the floor, and the sonde also hung in a tree but reachable.
Here is where the Swiss army knife would have been handy.
The cord is tough to tear apart.
This is the reason I have two RS41 sondes on my table.
And here are the two balloons.
The first is entirely intact.
The second only in parts.
And here we see the parachute which should have softened the fall.
Unfortunately, this one did not open correctly, and it fell quite fast.
And here it is still inside the balloon.
Now it is up to you to start the search or to build a surveillance station.
And if you want, you can enter the “hall of fame” on radiosondy.info because you
should enter your name if you found a balloon.
Search for HB9BLA, and you will find my two catches.
Still at the bottom of the list.
As the last step, I built a permanent housing for my Raspbi and the SDR receiver.
I used the same assembly as for my LoRa gateway with a tube from the do-it-yourself shop and
a 3D-printed holder.
Because it will run off mains, I included a small power supply.
And I added a DIY ground plane antenna, which I optimized using a vector network analyzer
and pliers to cut it to the right length.
This antenna is ok for the 100 km to the launch site.
Maybe we will meet once hunting for the same balloon.
Hopefully not during the night!
Meeting somebody in the middle of the night in nowhere can be scary!
So, if you hear somebody near you, just shout “Hello Guy with the swiss accent,” and
I know that I have nothing to fear.
As always, you find all the relevant links in the description.
I hope this video was useful or at least interesting for you.
If true, please consider supporting the channel to secure its future existence.
Thank you!
Bye
https://www.overlookhorizon.com/how-to-launch-weather-balloons/how-to-track-nws-weather-balloons/ https://www.weather.gov/upperair/radiosonde
http://mysondy.altervista.org/mysondygo.php https://www.thingiverse.com/thing:3932581?fbclid=IwAR2uWuwWE0YU9QPuAoWeeUYdh5MuswaHZ-LPI08AHvp2wniV91YYk7JG_bQ