Make a High-Altitude Balloon Tracker (Arduino)

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One of the coolest projects I have done so-far with my kids is a "near-space" balloon. That's not quite into space itself (100Km+) but so high that the sky looks black and you can start to see the curvature of the earth below you.

The Flickr set with the photos from our first launch is here:

This is a quick-fire slideshow of the photos from the balloon, formatted as a 2.5 frames/sec video. I'm having trouble embedding it so the link is here

In order to take this kind of photo you need to send a camera up to the stratosphere. Ours went 38Km (124,000 feet) straight up. This is easy enough: you attach it to a massive balloon, let it rise until the balloon bursts (due to the v. low pressure at the edge of the atmosphere) and then it will fall back to earth.

In order to see the photos that you have taken, you then need to find the camera afterwards. This is the trick.

Fortunately, at least in the UK and increasingly across Europe, the very helpful guys at the UK High Altitude Society ( have developed a distributed network of trackers who will receive a signal from your balloon, upload the data to a server and plot the position for you on a Google Maps based page (

In order to take advantage of this wonderful network of helpers, we need to build a tracker that will communicate with their equipment. That is what I will outline in this instructable.

There are plenty of rules and regulations regarding what you can fly and which parts of the radio spectrum you can use for various tasks. The approach I will use in this instructable is suitable for the UK under the rules prevailing in 2013. If you live elsewhere or you are doing this significantly after I write this instructable, please check the rules that apply to you. The guys at UKHAS are fantastically helpful.

So - let's build a radio-tracker.

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KrystofC21 days ago
Ugi. I'm from Montreal Quebec. I made a revolutionary concept. Maybe we can talk about it and work together ? We can Skype or FaceTime. First email me.
moein27 days ago

what if it makes collision with airliners ?

Ugifer (author)  moein26 days ago
You can only fly in the UK if you get permission. That is only given form places and wind directions away from major air corridors. Your flight is also notified to airmen and the maximum weight is quite low.

If you did actually collide, what would happen is that your payload would be destroyed with very little chance of any damage to the aircraft.
HF_ATL5 months ago

Very nice DIY tracker Ugifer! Thanks for the effort you've put on this.

Any idea if it can be modded to use with APRS AFSK instead of the 50baud regular FSK without exceeding the 32Kb flash for the atmel?

try looking at these.....

Ugifer (author)  HF_ATL1 month ago


Thanks for your comment - I'm sorry I missed it initially.

I am afraid I don't know the protocol for APRS but I'm pretty sure there would be enough flash space. The issue is more likely to be whether there is sufficient SRAM. If you could live without the SD card then I'm sure there would be enough of that too. However, the TinyGPS library and the SD card both use a lot of SRAM so you would need to be careful writing a sketch that uses both. That's why the telemetry includes the amount of free SRAM - for monitoring without using Serial (which itself also uses a buffer of SRAM).


Thaks Ugi :)

My only concern is that if the balloon lands behind a hill somewhere will it definitely be able to be located by someone somewhere, or do i need an SMS message on board that can communicate via satellite when the line of sight isn't too great. I also wondered if you knew the regulations as to how often you can transmit on 434.075MHz, as we will be constantly measuring data on board the balloon but not constantly transmitting data.

Ugifer (author)  jacob.hall.16121477 months ago

HI Jacob

Backup trackers are something that many people do use but without much documented success. If you are in the UK and using the centralised Google map, that will predict a landing point for you. If you lose contact fairly low then that should be enough for you to get close enough to re-establish the signal and get the exact location.

I did use a backup - an Android phone which was set up to respond to an SMS by sending its GPS location. However, because phone GPSs are generally not chosen for the ability to go higher than a cruising 747, they will often get very confused by the balloon flight (your balloon might go 3 or 4 times as high). The phone I used did respond but it took 20 minutes to reply, which was probably an hour after it had landed. We were in the car, driving home, by that point! Whether it actually had enough signal etc to respond from the field where we found it I will never know, but it might have.

There are two things to weigh-up here: you are getting a backup tracker, but it is costing you extra weight. I went with a phone because it could communicate and had a GPS but also had a camera, so I took a video of the flight using that. It was not as good as the still images but still interesting and justified the phone's trip beyond being a backup tracker.

For the 434MHz band, you can transmit continuously at up to 10mW (in the UK - I know nothing of elsewhere except that the rules vary). Your through-put is to some extent restricted by the 50-baud data-rate, which gives you a new data string every 15-seconds-ish. People do transmit at 300 and even 600 baud but generally the sensitivity is somewhat lower and there was no need for that using the data I was generating. I did test this board with 300-baud timing and it worked fine transmitting across the room. Whether it could transmit 25-miles straight-down I do not know but I believe the interrupt-based code in this instructable stands a reasonable chance if you adjust the timing in the code and the shift of the radio Of course you can always store extra data on the SD card and retrieve it later.


Hi Ugi,

I have all the parts ready. But im wondering how you find the balloon once it has landed. I am doing a university project with a limited budget with a balloon, and so need a cheapish solution. Is there a GPRS arduino piece or other equipment i could use to do this? Any help you could give would be appreciated.


Ugifer (author)  jacob.hall.16121477 months ago

HI Jacob

Not quite sure what you are asking here; the point of this tracker is that it transmits the GPS co-ordinates of your balloon throughout the flight. That lets you not only find your balloon but hopefully track it right through its trip (see the images in the last step).

If you are asking how you <i>receive</i> the signal then that is cheapest by using a Software-Defined-Radio dongle and appropriate software. There are links to that in the 'ible.

If you are launching in the UK then you are greatly assisted by a fantastic network of distributed receivers who will each upload your telemetry data to a central server where it it tracked on Google Maps. Again, see the links in the 'ible for more info.

Hope that helps. If not, just let me know.

Good luck with the flight!


Lloydy21 made it!7 months ago

Hi Ugi,

Great Instructable! Just got a question about setting up the payload document on High-Altitude Balloon tracking server. Where do I find the frequency and other data the site requires to track my payload? I had a look though the code but couldn't find anything. I'm almost done making my own as you can see in the attached photo. Great work on the instructable and best of luck for future endeavours.

Ugifer (author)  Lloydy217 months ago

Hi Adam!

Looks like you have all of the essentials in there already - although there are a few more key bits I would suggest:

Next to the crystal are two 4k7s. Those are the pullups for the 12c bus - you might want to populate those. 4k7 is ideal but if you have anything between that an 10k that should be fine. Also, do you have the 22pf caps for your crystal? I don't think it will work reliably without. If you want any of the LEDs to work then they will also need their resistors.

Thanks for posting the photo - I'll send you a 3m pro-membership by PM. Love that board in red!

I would strongly recommend getting online with the UKHAS irc crowd before you fly - they have much more experience than I have and can guide you through all the remaining steps.

The frequency is set by your NTX2 - yours is 434.650 MHz. If you used the same resistors as I did to drive the NTX2 then your shift should be around 450 Hz. You can only be really sure about that by measuring it but it doesn't matter too much - as long as the central frequency and protocol is right (434.650, 50 baud, 7-bits, one stop-bit, no parity) then people can adjust the shift as needed providing it's there or thereabouts.

Let me know if you are launching in the UK - I'd love to track this one if I can!



Lloydy21 Ugifer7 months ago

Thanks for the prompt reply!
The rest of the parts are on order, most of the parts I could scavenge from my spare parts drawer, which was really handy! :D
Thanks for the details regarding frequency, this is the first project I'm using the NTX2, so I'm completely new to using FM transmission protocols but eager to learn.
Unfortunately here in Australia there's certainly less people tracking these things, but hopefully I can figure this out. I'm not on any schedule for this so baby steps for me. I think the red looks great and is a nice change to the usual green. I use, they're by far the best fabrication service I've used, definitely worth a try! Thanks heaps for the 3month membership, I'm in the process of writing a few instructables and now I have more incentive to get them done :P

I hope to incorporate this into some of my autonomous robot projects until I'm ready with the balloon. In the process of adding to the board to integrate more sensors, and possibly include an USB to Serial via FTDI so I can update the firmware whenever I need to make changes. (Adding allocations for a geiger counter, Co2 and gyroscope. Can't really justify the gyroscope but heck, why not)

Can't wait to see your future project and wish you all the best for the future


Ugifer (author)  Lloydy217 months ago

Love the idea of using this with a robotics platform! Even if you did most of the control of the robot on another board, you have the UART free on your ATMega so you could easily use this board to manage some sensors & GPS then report back by serial.

I had a nose around dirtypcbs & they look great! I have usually used . Their cheap boards are only in green but they are almost exactly the same price as dirtypcb and I haven't had a bad board yet. They do also do a 5 x 10cm board which is cheaper than paying for 10x10 at dirtypcb if that's what you need. However, I often find I need several revisions of a board once I get it working and want to tweak it, so I might well use dirtypcb so I can use different colours for different versions!

If you want to update the ATMega on-board then I use a basic CP2102 module. They are a few dollars on e-bay and just plug in to the serial pins when you need. There is a similar module using FTDI which means you don't need a separate FTDI chip on-board for each device (& don't need to use surface mounted components). For a robotics board the size & weight doesn't matter but if it's going up in a balloon then there's not much point in having more board area etc than you need - no PCs to interface with a 38kM!

Would love to hear what you do with these.


cazpian10 months ago

Fantastic project, top notch instructable. Who did you use to fabricate your PCB and how much did it cost?

Ugifer (author)  cazpian10 months ago
Thanks cazpian - sorry for slow reply. I'm on vacation just now. I used Itead studio. Because the board is only 5 x 5 cm it cost less than £10 including postage for 10 copies. I used slightly thinner than normal boards for weight. I think it was 1.0 mm. If you need then fast then it's more expensive because you have to pay for courier delivery.

Let me know if you make a project based on this - or if I can help at all.

waymond9111 months ago

This is awesome!
I've been looking for a tutorial like this for a while!

I have never used the radiometrix modules before, but they seem like a good solution.

What did you use for an antenna for transmitting back to the SDR?

What documentation did you find regarding the NTX2 module?

Ugifer (author)  waymond9111 months ago

Hi Waymond - thanks for your comment.

The version I used has now been superseded by the NTX2B but lots of information on that and how to use it is available from UPU's web site here:

The datasheet for the NTX2 is here:

It is usual to use a quarter-wave ground-plane antenna, which I made from a length of 50 Ohm coax, with the braiding stripped away and soldered to a ground-plane made from copper tape on the bottom of my box a 164mm element made from the core of the coax extends below the ground-plane. The board is designed to allow direct soldering of the coax.

In the picture in the last step you can see the box I used. The drinking-straw you see supports the quarter-wave element while the little extensions on the corners expand the ground plane to a full quarter-wave in each of four directions.


halamka1 year ago

Why Arduino and microsoft? Why not Commodore with BASIC? (new commodore?) 0000 1101 is Return. 0000 1101 a BASIC program statement into into a memory line. Then type RUN.

Ugifer (author)  halamka1 year ago

I don't understand your comment I'm afraid.

I don't think Arduino it related to Microsoft - it's an independent Open Source development environment. Yes, you can run their IDE in Windows but also on a Mac or Linux box. The great thing about it is that it's a quick and easy way to program a microcontroller.

I was using BASIC on my BBC micro 30 years ago and it still runs, but it's a little heavy to send up in a balloon! Seriously thou', you could do all of this with a Pic writing in BASIC, and there may well be a BASIC compiler for the ATMeag328. I just don't know of one. I had the skills to do this with a '328 and Arduino. Others might well have preferred other systems but I don't have enough experience with those yet. You could use whatever system you preferred.


halamka Ugifer11 months ago
OK. This is where I am at designing a BASIC computer. 0000 1101 is ascii for RETURN. When return is pressed while writing a BASIC computer program, all the characters are then stored in a memory matrix reserved for programs. So , specifically, a flow chart for sorting program line numbers is run through. As on ATARI 2600 BASIC card the entire microprocessor program should be limited to about 1500 or so lines of binary code. JPEG or something similar would be written by other people. The small GB memory cards are JPEG (video compression matrix manipulation) format. The memory cards for PCs are secretly coded. The disc drives are fairly secret. Possibly made secret by Paul ALLEN of microsoft. The area of the us where these computers are built is san jose, not los angeles. Los angeles was where FORTRAN computers were built. FORTRAN is from the 1960's and 1970's. FORTRAN computers are more complex to build. I took apart some boards from what I think were FORTRAN computers. Many , many data busses and address busses.
amccarty511 months ago

Do you know if this tracker would work in the U.S. and what kind of camera did you use the could stand the pressure of going up that high

Ugifer (author)  amccarty511 months ago

As far as I can gather, nearly all digital cameras work fine. As long as it's in an insulated box (the blue foam box you see in the last step) it should be fine. Although the pressure is very low (8 mBar at max height in our case) as long as the camera isn't perfectly sealed it should be fine.

Light and compact is good because you don't want a heavy payload. Also using normal AA batteries is ideal because disposable lithium cells are considered more reliable than rechargeable LiPolys (although the latter do seem to work). Don't use normal alkaline batteries. They just stop working at low temperature. A Canon camera allows you to use the Canon Hackers Development Kit ( which is a good way to set your camera to take a still photo every few seconds etc.

As for the US, I don't know at all whether this transmitter would be legal. It depends upon spectrum allocation which is different in the US. Even if it is, I suspect there is not quite the same density of receivers in the US. However, you don't need many people to receive. One fixed station and one roving receiver might well be enough. My impression is that you need a amateur radio license to launch in the US. US launchers often use the APRS network which you cannot legally use in the UK.

Good luck launching!


Ugifer (author) 12 months ago

Wow! Thanks guys - and thanks to everyone who voted for us.

The girls will be chuffed to have a prize - not that I'm excited at all myself, you understand ;-) !

Thanks again.


halamka1 year ago

Why Arduino and microsoft? Why not Commodore with BASIC? (new commodore?) 0000 1101 is Return. 0000 1101 a BASIC program statement into into a memory line. Then type RUN.

dubbaluga1 year ago

Hi Ugifer and thank you very much for your detailed explanation! I have also spent some time on preparing my first space flight but due to a few other projects it has been postponed.

From what I have learned it seems to be the most difficult to track a flying balloon due to the big distance. Could you please let me know how you did the real tracking or your balloon? Were there any special devices such as a "Gattling Antenna" or a dedicated receiver unit involved or just the parts that were mentioned in the provided link (

Ugifer (author)  dubbaluga1 year ago

Hi dubbaluga - thanks for your interest.

All I used for my flight was an SDR dongle and a mag-mount antenna attached to the car. However there are really two separate types of tracking:

Firstly, there is tracking the balloon for the bulk of its flight. If you are organised then you don't need to worry about this part. If you use a tracker like the one I describe here that is compatible with the UKHAS receivers, load a flight document and tell them when you are flying (& what frequency etc) then there are dozens, probably hundreds now, of radio amateurs and balloon enthusiasts who will track your flight for you. Some of them have very fancy tracking antennas and receiving equipment that will be able to receive the signal from your balloon from a very long distance and in essentially any conditions. However, these can only track your balloon when they can "see" it, which means that near to the ground they will tend to lose your signal as hills and buildings come in between.

The part where you need to be involved is when the balloon is near the ground. If it's your flight then you will want to track it for the first few thousand meters as it rises. You will also want to get near to the predicted landing point once it bursts so that you can pick up tracking near the ground when the fixed trackers lose it. For that you need a portable setup and a car. I found that a laptop, an SDR dongle and a mag-monut was absolutely fine for that. I picked up the signal after landing and pinpointed the landing point to within a bout 3 meters. Because you are close at that point, very high quality equipment should not be needed. I did have a small Yagi directional antenna but I didn't need it so it never got used.


Hi Ugi,

thanks for your reply! That's something I didn't think off: just using the SDR dongle for testing the tracker myself and letting others do the dirty job. ;-) However, I have to find out whether there are people who can track balloons in Austria (my country of origin).

Once I talked to a person who is familiar with flying RC equipment and the Austrian law. He told me that officially one would have to register such a high altitude balloon flight. This would result in a certain time frame reserved for the flight. On the other hand, there is a lot of bureaucracy involved and just letting the balloon go into the air would most probably not cause much trouble. Air traffic control could not locate the balloon using a radar as it would simply disappear in background noise and in the unlikely event of a plain hitting the balloon it would be either smashed or vaporized depending on the location where it hits the plain.

Ugifer (author)  dubbaluga1 year ago

Hi - I tried to respond yesterday. Don't know why it's not showing.

There is at least one receiver in Vienna. I expect that if you contacted the guys at UKHAS and found out who it was in Vienna, they could probably arrange for more receivers in Austria for your launch.

We did request Aviation Authority clearance, as you need to in the UK. I'm afraid I don't know anything about the rules in Austria but the guy in Vienna who traks ballons may know more.



Lloydy211 year ago

Great intractable! I really do like the design of your custom board and the detail you put into the instructable! Made my own radio tracker similar to your own, I opted with using the GSM network as a backup GPS system if anything fails, plus it doubles by providing a internet uplink so I can view images and atmospheric data. I am however having a bit of trouble downloading the Edge files, would you be able to provide an mirror link or maybe a .zip with the files.

Look forward to seeing what you create next! :D

Ugifer (author)  Lloydy211 year ago

Hi Lloydy21

Thanks for your comment - interesting to hear from another HABer.

I did have a sort-of GSM backup in that the payload also carried an android phone that I could text and would text-back GPS coordinates. However, because the GPS doesn't expect to go so high, it takes about 20 minutes to recover once you get back to the ground - by that time we had already found the payload!

How high could you go before you lost GSM reception? I have heard that it drops off very fast with height.

I've added a second .zip file with the Eagles files inside. Let me know if that still causes problems.


lux4x41 year ago

Wonderful.... no words!! Only enjoy!!!

Ugifer (author)  lux4x41 year ago

Thank you for your comment - glad you enjoyed it. It was fun to do.

kisa721 year ago


Ugifer (author)  kisa721 year ago

Thank you!

jrd2101 year ago

Great Instructable BTW.

Ugifer (author)  jrd2101 year ago

Thank you! Looking forward to hearing about your project - if you do get clearance to launch then please come back and post a link to the photos etc. I never grow tired of seeing this type of thing!


This is the BEST project I've ever seen on instractable, I ALWAYS wanted to make a project like this but the problem is that I don't have boards electronics arduino or any resources like this near me. During the video amazing shots I've seen. and the moment of POP:
photo-2014-06-19, 10:11 PM.jpg

You, stop limiting your creativity! ;-) do it!

Ugifer (author)  • The Inventor •1 year ago

Thank you for your enthusiastic comment! Yes. I liked that shot too.


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