Building an ADS-B station

Complete guide to building an ADS-B station: theory, components, maximizing reception performance.


Focus in is on 1) ease of use, 2) good performance, 3) value for money. I assume you know nothing about radio, ADS-B and computers in general, so no jargon.
ADS-B means Automatic Dependent Surveillance Broadcast, aircraft transmit in-flight data such as identification, position and speed. System benefits other airspace users, and enables ground folks to track airplanes. For more info on how the system works, watch this Youtube video, or read the Wikipedia entry.
Signal reception is possible on a budget with RTL-SDR dongles, and building a 24/7 constant-on station is not harder than copying holiday photos to a computer.
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Elements of an ADS-B station


As a minimum:

1) computer running suitable software,
2) receiver,
3) antenna.

Additional components, such as preamplifiers and filters improve reception, and are detailed below.

Computer


Any PC (laptop or desktop running Windows, Mac or Linux) can be used with suitable software to display received signals. If you want to see whether ADS-B is for you, only a $10 RTL-SDR dongle and some software setup is required: the process is well documented online with many free software packages available e.g. Planeplotter with dump1090.
Most stations are on 24/7/365, forwarding info to data aggregator sites such as FlightAwareFlightRadar24Planefinder or ADS-B Exchange. In return for your efforts, for instance with FlightAware, you get an enterprise account worth $90 dollars (per month), so if airplanes are a big part of your life, your own ADS-B station is well worth the investment. Other sites also offer premium accounts, and you will get the benefits even when you're not home or via a smartphone app, because you'll have more info of a flight including past performance, delays and historical flight times.



Computers use a lot of electricity, for example, my 15.6" laptop uses 60W an hour. Big desktop computers will use much more power.
Recommended solution, not only for the environment, but also for your wallet and blood pressure (configuring a PC-based station is much, much more complicated) is to order a Raspberry Pi 3 microcomputer and run PiAware.
For constant-on use, savings in electricity - a Pi 3 uses less than 2 Watts - will pay for a Raspberry in two-three months (and it's a wonderful platform for all sorts of things).
From now on, I assume you'll be using a Raspberry, but don't let that deter you - equipment choices and underlying principles are just as applicable to PC users.
Cheapest ($70), bare minimum ADS-B station setup needs and looks like:



From left to right:
- MicroSD card and adapter,
- Power supply,
- Computer: Raspberry Pi 3 board,
- Generic unbranded RTL-SDR dongle,
- cable and antenna (comes with dongle).
Anything else is not strictly necessary, just the icing on the cake, but will make your life easier and/or get more results.
Buying components separately will be eventually more expensive than buying a "kit", but not all kits come with a microSD card and Internet cable for easy connection to home network (more on that later).
If Amazon or eBay is your hunting ground, the Vilros Starter Kit in the image above for $65 does the job. However, it does not come with an Internet cable, which is $5-10 extra depending on length, and might be unnecessary if you already have one, or you'll be using WiFi.
Starting anew, I'd order a ModMyPi's Starter kit for $73 shipped in a heartbeat over anything else, because everything for an ADS-B station and to enjoy a Raspberry Pi 3 on its own is in the kit. Quality of components is light years better than a Vilros (I use both), and I had no problems whatsoever after five months' 24/7 constant use (detailed review here).



All Pi 3s are designed to run without heatsinks, but most kits include them, because users heatsink a Pi for safety. Cases with fans are grossly unnecessary and detrimental to receive performance, therefore are NOT recommended. "Ultimate kits" with lots of electronic gizmos are best left to a later date.

Software


PC: Follow rtl-sdr.com's tutorial for a taster, warning: process is not easy. 99% of ADS-B enthusiasts (my estimate) use a Raspberry Pi for a reason.
Raspberry Pi: PiAware image is free, and the easiest path for beginners. Detailed installation steps here, roll down to Section 2 "Install PiAware on your SD card", which is not harder than opening the fridge. If you can read this, you can do it, follow steps, download is 620 MB, about 2 hours on a slow connection.




Wizardry with custom installations, "compiling" and different "forks" are better left to Linux experts. Write the memory card, insert card into Pi3, plug in power, sort out data transfer and enjoy.

Data Transfer


Information provided by an ADS-B station can be viewed on any device sharing the same network connection - any tablet/smartphone/PC can be used to see which planes does what. Supplying the same data to ADS-B websites is called "feeding" in enthusiast speak.
Raspberry Pi 3 has built-in WiFi, Pi 2 does not. Wifi setup on a Pi 3 takes a few minutes, guide is included in the PiAware download. Raspberry Pi 2 can also do Wifi, with the addition of a USB modem and antenna, $3 solution with external antenna connector in image below. Wifi range can be extended with an aftermarket directional antenna, but that's way beyond the scope of this post.



Wifi is more convenient and allows freedom to place station wherever you want. On the other hand, in urban and suburban areas, wireless frequencies can be really congested, like everyone using the same lane on a motorway.
Wired connection with Internet (officially called Ethernet or RJ45) cable is better on the long run, one less thing to worry about. Direct connection is literally plugging in two ends of the same cable, one end goes into the Pi, other end goes into router (flat box from Internet company).

Which receiver?


Depends on how much money you got, and whether you want to use the dongle for general radio signal reception as well. Cheapest is $8 and homemade antennas, then the sky and wallet depth is your limit.
Dongles in the image have been tested and work for ADS-B:



For less than 10 dollars, a generic RTL-SDR dongle will do the job perfectly - albeit a small modification to antenna will be necessary to get better results (see images later), but as a low-cost starting point, $8 is hard to beat.
More expensive RTL-SDR dongle bundles come with telescopic antennas and long warranties, and are also usable for other signals. I recommend a premium RTL-SDR dongle bundle, either the Nooelec SMArt ($28 at manufacturer, $27 on Amazon), or rtl-sdr.com's $25 v.3. Both perform on the same level for ADS-B reception, both come with antenna suitable for airplane signals, both are plug-n-go.
The Pro Stick comes with an onboard amplifier ($17 on Amazon), and an excellent choice for ADS-B and general radio use - more info in my previous review.
The Pro Stick Plus ($21 on Amazon) is better than any other dongle for ADS-B. My review here, know that it does not come with any antenna, just like its orange brother, and will be borderline unusable for anything else but ADS-B reception.
Even more expensive options ($100 or up) are the SDRPlay RSP2, any receiver from the AirSpy stable, or dedicated solutions such as the Mode-S Beast  - I have no experience with them for ADS-B use, so can't comment.
Avoid any dongle with E4000 or FC0013 chipset, e.g. XTR or XTR+ from Nooelec, Outernet's dongle, or EzTV645: they generally don't work for ADS-B.

Amplification


Signal can be amplified by either an integrated onboard chip (Pro Stick and Pro Stick Plus) or by an external preamplifier connected with cable to receiver:




Preamplifiers are also called LNAs, short for Low Noise Amplifiers. "Noise Figure" in radio is how much thrash the preamp adds to signal, expressed in dB, lower number is better, less than 1dB is OK. TV signal amplifiers are not suitable, even when packaging says "low noise".



The market is awash with cheap (read less than $10 and reportedly horrible) preamps, the only boards I have experience with, and recommend are Adam's LNA4ALL, Janilab's preamp and novak5x's LNA. The last two cover the tuning range of RTL-SDR dongles, so a good choice for general use as well.
If $50 won't elicit shrieks from your wife or you yearn for a semi-pro preamp, Uputronics's 1090 Mhz filtered preamp will serve you, your kids and future generations well - my review here.
Bias-T, also called phantom power, means that the receiver is sending power down the coax cable to an antenna-mounted LNA. Currently, the only RTL-SDR dongle capable of this feature is rtl-sdr.com's v.3.

Filtering


A filter in radio is essentially the same as the coffee machine version: catches bits and pieces you'd rather avoid in the morning wake-up brew, and lets the good stuff through (coffee or signal).
Whether you need a filter depends on your environment. 1090 MHz bandpass filters (e.g. Flightaware filter on left, $20 on Amazon) only pass a narrow range through and block everything else. An FM bandstop filter kills commercial broadcast FM interference.



Adding a filter for $15-$20 is the cherry on the cake, e.g. I had 4% more reports with rtl-sdr.com bandstop filter in a recent test.

Adapters


Radio uses lots of standards to connect various components together. Adapters are only necessary if you're using an aftermarket antenna, or want to build an antenna to be used with an existing setup.
Manufacturers sell necessary adapters, like rtl-sdr.com offers a pack covering most standards for less than $20. Personally, I'm using and admittedly a great fan of Nooelec pigtails, never ever had to worry about reliability with them. Individual adapters can be bought on most online marketplaces.

Antennas


Antenna receives the signal from aircraft, so it's the most important part. In case you wonder, wavelength is 27.52 cm for ADS-B at 1090 Mhz, and antennas are referenced to wavelength in radio.
Supplied antennas and mounts are a great starting point: Small black fixed antenna works if you cut it back to 65 mm from top to screw, so it becomes a quarter-wave antenna. Telescopic antennas can be extended to a particular length, and every mount can be used with wire and willpower to make a half-wave or 5/8 antenna, which lengths pull in more signals than a quarter-wave. Read Easy ADS-B Antennas for more info and images.
Placing mount on a metal surface will help to receive more signals - if mount snaps and hard to lift, it's OK.



Nooelec also sells smaller and larger ADS-B antennas called "Discovery", these are primarily aimed at light aircraft pilots, not for terrestrial use. The $6 larger one in the image above is also good for general radio reception with strong local signals.
Telescopic antennas with a suitable connector type (SMA Male for Pro Sticks, v.3 and SMArt, adapters required with others) are a cheap alternative; I use the $3 Nagoya knock-off above (exactly half-wave when collapsed) with great results. SMA Male is also the connector standard used on several handheld transceivers and receivers e.g. Icom, if the antenna can be screwed off and has a center pin, it will work.
Warning: Wifi antennas have no pin, called SMA RP (Reverse Polarity), they won't work out of the box (add a 4mm length of coax conductor inbetween to make them function).



Specialist ADS-B antennas are built for the job; Flightaware's large 26" antenna for $45 dollars is built extremely well, has high gain and comes with a mounting bracket.
Adam's ADS-B antenna is a safe choice for $27 shipped, because due to its design, connected electronic components can not be damaged by electrostatic discharge. Image below from Adam's page, because mine is on the roof:



However, it requires soldering and performance was only on par with a half-wave when I tested it - which matters little in an unattended or remote setup, where reliability is of the utmost importance.
No matter what you choose, always try to place antenna outside, as high as possible, without any obstructions. Signal from planes are line of sight, antenna must "see" aircraft, clear line of sight is surrounded by red in image below:



A comparatively bad antenna will be better in a good location than a good antenna in a bad location - antenna placement is the most important thing for ADS-B signal reception.

Maximum range


How far? The most common question.
Range depends on antenna height above ground and obstructions between antenna and aircraft, such as trees and buildings. That's the reason commercial and military antennas are located on hilltops or on top of tall buildings.
Check heywhatsthat.com for an estimate of range for a location, forum thread how to use the site here.
Due to curvature of earth, it's unlikely you'll get more than 400 miles (if you occasionally do, it's because of a phenomenon called atmospheric ducting, but that doesn't last).
From a first-floor location (161 m above Mean Sea Level), I get a maximum of 160 mile range in a particular direction and barely anything from other directions, because the house blocks the signal with antenna on the windowsill.
Wall represented by red line in image below:



Local conditions will also have an influence on your maximum range, so if heywhatsthat blurps out a maximum of 200 mile range, and you only get 150 miles, don't worry: ideal doesn't exist in real life (Scarlett Johansson is an exception).

Do it right


System performance will be determined by the following factors, in order of importance:

1) Antenna position and elevation. An antenna with a clear view of the sky, higher up will outperform an antenna lower down with restricted line of sight. For example, a $100 antenna will pull in less position reports taped to a window indoors than a $1 homemade antenna fixed to the chimney.
2) Antenna type. Always will be the individual's compromise.
3) Amplification and filtering. This will almost always add extra range and position reports IF used correctly - buying the best gear and using long lengths of coax cable is just a waste of money due to coax loss.
4) Circumstances and attitude. Even if you can financially afford the best, your wife/husband, landlord or neighbor might disapprove. A Pro Stick Plus might not be available, or you deem making antennas too cumbersome, or you're afraid of heights and climbing a ladder fills you with dread. Everyone is different in a different way.

Money, money, money


You get what you pay for.
Preamps, filters, 12-bit receivers like an AirSpy or RSP2 will aid in pulling in more signals, but at a cost.
After a point, which I think is around $100 dollars total, a small performance increase will cost a lot. For example, in my previous test, the $45 FlightAware antenna had 22% more position reports than an antenna which comes for free when you spend less than $30 for a premium RTL-SDR dongle bundle.
An other independent test also had similar results, namely that an $150 AirSpy had double the message rate of a plain $8 dongle.
Plug-n-go kits are available on ebay and other online marketplaces, if you're tired of reading by now, and have $200 lying around, order one from Wifiexpert with a Pro Stick and filter or Pro Stick Plus.
For examples below, I assume you already own a Raspberry Pi 3 and back-end computing is up and running, so only variables left are the receiver, connection between receiver and antenna, and antenna.


Cheapest


Any generic RTL-SDR dongle for less than, or around $10, with modifications. All of these dongles come with a small black antenna and 3 foot / 1m cable. Search your favorite online marketplace for R820T2, some examples off eBay:



My first dedicated ADS-B station used a similar dongle with a Pi2, magnetic mount and half-wave antenna made from electrical cord wire and tape, placed outdoors on the windowsill on a metal cookie tin.

Easy and safe


Nooelec SMArt bundle. Comes with 6.5 foot / 2m quality antenna cable with magnetic mount and extendable telescopic antenna.



Screw components together, same story then: metal tin, place outdoors, be merry. Two-year warranty with dongle - peace of mind.

Easy with upgrade path


rtl-sdr.com v.3 premium dongle kit. Identical performance and just as easy to assemble as a SMArt, but only 3 foot / 1m cable and 6 months warranty. Adding length to cable is easy, and it's unlikely manufacturer won't replace dongle on the 184th day.



Plus it has a unique feature called bias-T, so for general radio use and ADS-B at the same time, a v.3 with a bias-T wideband preamp e.g. novakx5 LNA is a compelling solution for $60 total, offering the best of both worlds.

Affordable best performance


FlightAware Pro Stick Plus and a homemade antenna.
This combo would be my choice for maximum ADS-B performance for the minimum amount of money.



Requires SMA to F female adaptor or pigtail if you don't want direct coax connection, two F-connectors and length of satellite TV coax cable. Setup enables the resulting antenna to be placed outdoors. However, this solution involves cutting coax and building an antenna (my guide here), tasks which might be too complicated for a small minority of readers.



For less than $20, this setup will pull in more position reports than any other RTL-SDR dongle due to onboard amplification and filtering.

Max performance


FlightAware equipment: Pro Stick Plus and large antenna with adaptor.
From any location, this combo will pull in the most signals, as long as coax run is kept reasonably short, and you might need to adjust gain settings in software for best results.
Say again: use minimum length of cable between receiver and antenna. A lot of indoor-only folks just tape antenna to window with a PSP and get excellent results - amplification, filtering and high gain works, but the setup will be much better if placed outdoors.

Choices by price


Starting anew with a Pi 3 kit in hand, say $70 already spent:
$10: generic dongle with homebuilt antenna. Learn the ropes.
$20: for ADS-B only, Pro Stick Plus with homebuilt half-wave antenna.
$30: for ADS-B only, Pro Stick Plus with extendable telescopic. I'd seriously look at a premium dongle kit in this price range, there's much more to discover with a general use dongle, but ADS-B performance will be nowhere near a Plus.
$50: rtl-sdr.com v.3 bundle with bias-T wideband LNA at antenna. Good for ADS-B, and unsurpassed for the cost between 1-1800 MHz. A Plus with Flightaware antenna works out to around $60-$70, and a no-brainer if your homepage is your station stats, but for 10-30% less position reports, you gain the possibility of good performance across most of the tunable range of RTL-SDR dongles.
I could go on, but choices depend on the person asking the question, so comment below.

Closing thoughts


I've written this post to provide an overview and to show choices in terms of equipment, but please realize that every location (just like every reader) is different.
ADS-B signal reception is fun. Fortunately, lots of people agree with the above sentence, and your questions or success story can be shared with like-minded souls by commenting below, in a Facebook group, on reddit, or in discussion forums.

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