Build your own ADS-B receiver: Raspberry Pi, stick and antenna

On the flight tracking map, you see what is flying above you – but where do the dots actually come from? A large share of them comes from hobby stations on roofs, balconies and attics. If you want to build your own ADS-B receiver, you don’t need a soldering iron: A Raspberry Pi, a USB receiver and a suitable antenna are enough. This guide shows you which parts have proven themselves, where the antenna belongs, what software exists and how to pass your data on to flight tracking services.

The short answer: what you need

A DIY ADS-B receiver consists of three core components: a small computer (usually a Raspberry Pi), a software-defined radio (SDR) stick that receives the radio signals on 1090 MHz, and an antenna tuned to that frequency. The computer runs decoder software that reads the aircraft’s identifier, position, altitude and callsign out of the raw signals. Optionally, feeder software sends the data to flight tracking networks.

FlightAware puts the cost of the parts for its build guide at around 100 US dollars, or 80 euros, and estimates about two hours for the build. How the technology behind it works – that is, ADS-B, Mode S and MLAT – is explained in the basics guide Flight tracking with ADS-B for spotters. This one is about the practical build.

The hardware at a glance

Which parts you need specifically depends a little on which service you start with. The guides from FlightAware and Flightradar24 agree in their basic outline, though.

Component	What it does	What to look out for
Raspberry Pi	Computer for decoder and feeder software	FlightAware lists Pi 3, Pi 4 and Pi Zero W; check your service’s requirements beforehand
Power supply	Stable power in continuous operation	FlightAware recommends 5.1 V and 2.5 A; newer Pi models sometimes need more
microSD card	Operating system and software	FlightAware lists at least 8 GB
SDR stick	Receives and digitizes the 1090 MHz signal	common: RTL2832U chip with R820T2 tuner
Antenna	Picks up the signals	tuned to 1090 MHz, as high and clear as possible
Coax cable	Connects outdoor antenna and stick	as short as possible, FlightAware lists typically 5 to 20 m
Optional	Filter, enclosure, network cable, surge protection	Filter only if there is interference, surge protection for outdoor antennas

The SDR stick: the heart of the station

Originally, the inexpensive USB sticks were meant for DVB-T television. Hobbyists discovered that the RTL2832U chipset can capture a wide frequency spectrum as raw data – that is where the term RTL-SDR comes from. For ADS-B, the combination of RTL2832U and R820T2 tuner has caught on above all.

There are optimized variants specifically for ADS-B. FlightAware offers, for example, the Pro Stick with a built-in preamplifier (19 dB gain) and cites a performance increase of 20 to 100 percent over conventional RTL-SDR sticks. The Pro Stick Plus additionally has a built-in bandpass filter for 1075 to 1105 MHz that attenuates signals outside this range by 30 dB.

The antenna: more important than any other part

This is where it is decided whether your station hears 50 or 400 kilometers. ADS-B signals travel in an almost straight line and pass poorly through walls, roofs or trees. FlightAware puts it clearly: The antenna needs a clear view of the sky, and outdoor rooftop installations are the most effective – with ranges of over 400 kilometers.

The simplest antenna is a rod with a quarter of the wavelength. At 1090 MHz, the wavelength is around 27.5 centimeters, and a quarter of that is about 6.9 centimeters. This is exactly the value FlightAware also recommends if you use a stick’s telescopic antenna: Collapse it to 6.9 cm, don’t extend it fully. If you want more range, reach for ready-made outdoor antennas for 1090 MHz or build a collinear antenna from several segments.

Indoors or outdoors? The location question

Before you run cables through the house, an honest look at the pros and cons is worthwhile.

How far your antenna can theoretically hear depends on its height and the flight altitude. You will find the calculator for the radio horizon in the guide to flight tracking. As a rule of thumb: You hear aircraft in cruise from far away, aircraft on short final only if your antenna has a view of the approach corridor.

The software: ready-made image or your own setup

On the software side, you have two paths. Both work; they differ mainly in how much you control yourself.

Ready-made feeder images are the quickest way in. With PiAware, FlightAware provides a complete operating system image for the Raspberry Pi, and Flightradar24 does the same with Pi24. You write the image to the memory card, plug everything together and register the station with the respective service. Decoder, local map and data sharing are then already set up.

Your own setup is worthwhile if you want to supply several services or get in deeper. The basis is a regular Raspberry Pi operating system, on which you install a decoder and then the feeder packages of the services you want. Many common decoders go back to the original dump1090; an actively maintained successor is readsb. It supports RTL-SDR sticks and other SDR types and delivers the data in common formats such as Beast or JSON. As a web interface for it, tar1090 is often used, which shows the aircraft on a local map in the browser.

Step by step to your own station

The process follows the PiAware guide from FlightAware. With Pi24 from Flightradar24, the steps are very similar.

Sharing data: what you get out of it

Technically, you don’t have to give your data to anyone – the station also runs purely locally. Most hobby stations do supply at least one network, though, and there are solid reasons for that.

• FlightAware automatically gives feeders a free Enterprise account and shows you detailed statistics on your station’s performance.
• Flightradar24 also offers registered stations a free subscription in return for the data supplied.
• ADS-B Exchange cites as benefits, among other things, access to MLAT, a leaderboard for comparing stations and a discount that feeders can pass on. The service explicitly addresses stations that already supply other networks.

On top of that comes the network effect. For aircraft that don’t send their own position via ADS-B, the services calculate the location by multilateration from the arrival times at several stations. FlightAware cites at least three receivers that hear the signal at the same time. The denser a region is covered, the better this works – especially at low altitude around airports such as Frankfurt, Munich or Düsseldorf.

What you do with your station as a spotter

Your own station makes you independent of how any single service presents things. On the local map, you see what is currently moving around you – straight from your antenna, without a detour through a server. A few ideas for everyday spotting:

• Keep your home airport in view: If you see early in the morning from which direction the first approaches come, you know which runway direction is in use. Why that is decisive for your spot is explained in the guide Understanding runway direction in use at airports.
• Collect registrations: Every aircraft sends its fixed 24-bit address along. The registration can be derived from it – more in the article Understanding aircraft registrations.
• Learn to read callsigns: The station shows the callsign, not the flight number from the ticket. The difference is explained in Callsign and flight number.
• Spot rare visitors: Widebody jets such as the Boeing 747-8 or the Airbus A380 you can often recognize on your map while they are still far out in cruise.
• Put emergency codes in context: Squawk 7700, 7600 or 7500 also show up in your raw data. What is behind them is covered under Squawk codes 7500, 7600 and 7700.

If you also use the big platforms, you will find an overview in the flight tracking apps comparison.

Legal matters and safety

An ADS-B receiver doesn’t transmit anything itself, it only listens. Still, there are two points you should know.

Legal situation in Germany: The Telekommunikation-Digitale-Dienste-Datenschutz-Gesetz (TDDDG, the Telecommunications Digital Services Data Protection Act) regulates an eavesdropping ban in § 5. Under it, a radio device may only be used to listen to messages intended, for example, for the general public or an indefinite group of people; the content and reception of other messages must not be passed on. ADS-B is an unencrypted broadcast to all receivers in range, and private receiving stations are widespread. We don’t know of a conclusive classification by courts or authorities, though. How that looks for voice radio is covered in the article Listening to airband radio: the legal situation.

Safety when mounting: Working on the roof is dangerous. Secure yourself, never work alone and, when in doubt, have professionals put up masts. For outdoor antennas, FlightAware lists surge protection as sensible accessories; for questions about lightning protection and grounding of antenna systems, a licensed electrician can help.

Common mistakes when building it yourself

• Antenna behind glass and concrete: Modern low-E glazing and reinforced concrete strongly attenuate 1090 MHz. If range disappoints, it is almost always down to the location.
• Cable too long and thin: Every meter of coax cable costs signal. Better to bring the Pi closer to the antenna than to run a long cable.
• Weak power supply: The SDR stick draws power over USB. A power supply that is too weak leads to crashes and data gaps – take the recommended values seriously.
• Telescopic antenna fully extended: For 1090 MHz, it belongs collapsed to around 6.9 centimeters.
• Location not entered: Without the correct position and antenna height, your station can’t take part in MLAT.
• Filter on principle: In the countryside, a filter can do more harm than good. Measure first, then filter.

Conclusion

Building your own ADS-B receiver is one of the most rewarding projects for aviation fans: manageable cost, little tinkering and an immediately visible result. A Raspberry Pi, an SDR stick and an antenna are enough, and ready-made images from FlightAware or Flightradar24 take the software work off your hands. The antenna location makes the biggest difference – the higher and clearer, the farther you hear. If you share your data, you improve coverage for all spotters in the region and get upgraded accounts for it.