SDR beginner roadmap: tracking ADS-B aircraft with a $40 dongle
SDR beginner roadmap: tracking ADS-B aircraft with a $40 dongle
If you have just bought an RTL-SDR dongle and are wondering what to do first, skip the FM radio and go straight to aircraft. ADS-B — Automatic Dependent Surveillance–Broadcast — is the transponder protocol airliners use to broadcast their position, altitude, speed and callsign to anyone listening. Every commercial aircraft over Australia is transmitting it right now, unencrypted, on a single frequency, and a modest receiver can decode it within minutes of setup. It is the ideal first SDR project: one frequency, forgiving equipment requirements, and a result you can see on a map the same evening.
Why ADS-B first
Most radio hobby starts fail at tuning: you hunt across bands, hear fragments of static, and lose interest. ADS-B removes every one of those failure points. Everything happens at 1090 MHz, so there is nothing to hunt. The signal is digital, so decoding is automatic — software does the work, you watch the map fill in. And the payoff is immediate: position reports streaming from aircraft 100, 200, sometimes 300 kilometres away, plotted in real time.
A useful first evening, from a write-up of a minimal ADS-B tracking setup by a self-described total beginner, looks like this: dipole antenna cut roughly to length for 1090 MHz, mounted vertically (ADS-B is vertically polarised), SDR software tuned to 1090 with sensible gain, and the distinctive pulsing patterns of ADS-B frames appearing on the waterfall within minutes of moving the antenna near a window. No filter, no amplifier, no tower on the roof. That is the right mental model for step one — get a signal first, optimise later.
The hardware path, in stages
Stage 1: the dongle you already have
Any RTL-SDR dongle from the common RTL2832U family will receive 1090 MHz, though older ones with the R820T2 tuner are working near the edge of their range and benefit from direct sampling tricks. The current RTL-SDR Blog V4 handles 1090 MHz natively and is the default recommendation for new buyers. Coupled with a cheap telescopic antenna and a window with a sky view, it will show aircraft immediately in a suburban setting.
Software choices at this stage are simple. On Windows, SDR++ or ADSB# feed a decoder; on Linux and macOS, dump1090 and its forks (dump1090-fa, readsb) are the standard — they turn the raw samples into aircraft table and feed a map. You can be decoding inside twenty minutes.
Stage 2: the antenna — the single biggest upgrade
If you do only one hardware upgrade, make it the antenna. ADS-B at 1090 MHz is line-of-sight: range is mostly a function of how high and how clear your antenna's view of the sky is, not raw receiver gain. A dedicated 1090 MHz collinear or ground-plane antenna, mounted outdoors at roof height with clear horizon, can quadruple your aircraft count versus an indoor whip. Our 1090 MHz ADS-B antenna is purpose-cut for the band, and mounting it as high as practical matters more than any other single decision.
A note on antennas for absolute beginners: a quarter-wave ground plane for 1090 MHz is about 69 mm of vertical wire over a flat metallic reflector. It is a classic DIY build, costs almost nothing, and performs respectably — a good weekend project even if you later buy a proper antenna.
Stage 3: filtering and low-noise amplification
Once the antenna is good, two problems appear, and both have the same root cause: everything within tens of megahertz of 1090 MHz is louder than the aircraft.
- Strong out-of-band interference — nearby FM broadcast, DAB, and especially the strong bands around 1090 (including other 1090 MHz users and harmonics) can overload the dongle's front end and desensitise it. An FM-notch plus bandpass filter for 1090 MHz solves this class of problem. Our ADS-B LNA with FM notch filter combines a low-noise amplifier with the filtering in one inline unit.
- Cable loss — at 1090 MHz, even a few metres of cheap coax costs you significant signal before it reaches the receiver. The standard fix is to put the LNA at the antenna end of the cable, where it restores signal ahead of the loss, and power it over the same coax (bias-tee) so you need no extra cabling to the mast.
The ordering matters, which beginners frequently get wrong: antenna height first, amplifier second, filter alongside it. An amplifier on a bad indoor antenna amplifies a bad signal; a filter on a rooftop antenna turns a good setup into a great one. Community discussions on the FlightAware receiver forums show the same pattern of questions in nearly every beginner thread, and the consensus answer rarely changes.
Stage 4: feeding and sharing
Once you have a stable decode, you can contribute to the global tracking networks. Sites like ADS-B Exchange run on volunteer receivers and publish feed setup guides for exactly this purpose, and FlightAware's PiAware feeder is the other common path. Feeding is optional but rewards you: most networks give contributors free or enhanced access to their premium tiers, and your receiver becomes a node in a global sensor network assembled entirely from hobbyist hardware. Legally, receiving ADS-B in Australia is passive listening of a public broadcast — you are decoding transmissions that aircraft make to anyone with a receiver.
What you will actually see
A well-sited suburban setup with a rooftop antenna typically holds 100 to 200 aircraft simultaneously across a few hundred kilometres, with regional jets on approach resolved down to individual runway assignments. Rural sites trade raw counts for extraordinary single-antenna range — aircraft overhead at cruise altitude can be received well past 400 km with clean hardware. Watching a weather front move through is genuinely informative: you see diversions and holding patterns develop in real time, hours before they make the news.
The same station grows with you. The antenna and filter chain that decode ADS-B today are the foundation for listening to ACARS text messages from aircraft, satellite weather downloads, and later the wider SDR hobby — the SDR capability guide maps that broader territory if you want the full picture.
Budget summary
A realistic three-stage path, in AUD terms:
- Start: existing dongle plus bundled telescopic antenna — $0 extra.
- Second step: dedicated 1090 MHz antenna plus low-loss coax — the largest per-dollar gain in the whole project.
- Third step: filtered LNA at the mast — transforms good range into consistent range, especially in RF-noisy suburbs.
If you are buying from scratch, our RTL-SDR v4 kit bundles the dongle, antennas and cabling needed for stage one and two, so the only later purchase is the masthead filtering and amplification.
Common beginner mistakes
- Chasing gain numbers. More amplifier gain is not better; too much gain overloads the decoder and paradoxically reduces message counts. Tune gain to your site.
- Indoor antennas near metal. A foil-backed insulation layer, ducted heating, or a metal roof between you and the sky costs more range than any component upgrade can recover.
- Skipping the filter in urban areas. If you live within a few kilometres of a broadcast tower, a filter is not an optimisation — it is a requirement.
- Ignoring connector quality. SMA finger-tight is correct; pliers-tight damages the centre pin and introduces intermittent faults that look like software bugs.
Start simple, get the first aircraft on the map, and then upgrade in the order that matters: antenna, location, filter and LNA. ADS-B rewards that sequence, and unlike most radio projects, it rewards it on the very first evening.
Receiving ADS-B is lawful passive listening in Australia. This article is general information, not legal advice.