Tag: radio

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ADS-B SDR

Receiving aircraft ADS-B (position) signals – part 4 (antenna up on roof)

Antenna up on roof

Coming from part 3, where I wanted to move the antenna, I finally got the antenna up on the roof. Our chimney was decommissioned by the previous owners and as far as I can tell, there isn’t brick under the siding (also why does our chimney have siding on it). So it is sitting a little lower than it should be but it is basically at the highest position of the roof. This has dramatically increased the ability to receive aircraft ADS-B signals.

Results

The results are pretty amazing. We’ve had bad weather for a week now but it’s going to be a clear day today. As of 9:12AM, my Raspberry Pi PiAware ADS-B signal receiver sees 116 aircraft, of which 103 are reporting positions. It is receiving 607 messages per second. The map looks like this:

116 aircraft signals received, 103 with position. farthest out is 190 NM.

You can see aircraft lining up to arrive into KDEN spaced out at regular intervals. It’s also picking up 3 planes on the ground at KBJC which is the closest airport to the antenna.

FlightAware has a cool radar type map that shows positions by compass direction and distance. The numbers speak for themselves.

Before

Max distance reported is in the 100-150 nm bucket (327 total reports)

After

That same 100-150 nm bucket now has 24k reports

Interesting features

While typing this post, the position count increased to 118. There are some interesting features I’m seeing – a survey plane over the Breckenridge area, a lot of planes on the ground at KBJC (not line of sight to my antenna), and even plane on the ground at KDEN (KDEN is definitely not line of sight to my antenna).

Survey grid being flown by N94S

Planes on the ground at KBJC

I see 4 Cessna/trainer type planes waiting for takeoff for 30R at KBJC. I’m even picking up a corporte jet type aircraft on the ground by the hangars (N4840W). None of this is line of sight to my antenna. There’s a chance the ADS-B signals are bouncing off buildings or something. I shouldn’t be seeing these.

The elevation profile to 30R at KBJC. Antenna on left, run up area on the right. Barely not LOS (line of sight).

Plane on the ground at KDEN

United UAL364 / N802UA (an Airbus A319) on the ground on runway 16L/34R heading south
Elevation profile to south end of 16L/34R at KDEN. Antenna on left, 16L/34R on right. Definitely not LOS. No idea how I’m picking up these signals. I see a plane on the ground at KDEN multiple times a day since moving the antenna.

151 planes!

I started this post around 9am on 4/18. Just before noon, there were 151 planes being tracked by my PiAware station! 773 messages per second. Notice that plane way out there over west central Nebraska – that’s probably 210 NM out!

Conclusion

Moving my FlightAware ADS-B antenna to the roof drastically increased the range and messages received. As a reminder from when I detailed the equipment in Post 2 – the antenna feeds a 1090MHz ADS-B filter, which in turn feeds the FlightAware Pro Stick. I don’t think I’ll make any other changes to the system other than put it on a battery with solar charger.

Categories
ADS-B SDR

Receiving aircraft ADS-B (position) signals – part 2

Welcome back from part one (Receiving aircraft ADS-B (position) signals)! Now that you have all the required equipment – what do you need to do to set it up? Thankfully, the folks over at FlightAware have made this super easy. FlightAware provides a flight tracking platform that is mostly fed by users like me (and soon to be you!). In return for feeding them data, they will give you a free enterprise subscription, which is normally $89/month. It adds a lot of tracking abilities which are great for aviation nerds like myself. To get the most data possible, they have put together some great getting started guides, which I will link here – https://flightaware.com/adsb/piaware/build. The short version is:

  1. Write the Piaware operating system to your SD card
  2. Either enable WiFi or plug into your router
  3. Plug everything in
  4. Claim your station on FlightAware.com after a few minutes
  5. Watch the data start flowing!

Here is a picture of the most basic setup possible:

Simple ADS-B receiver setup with RTL-SDR and 1090 MHz antenna
Simple ADS-B receiver setup with RTL-SDR and 1090 MHz antenna

To really increase your reception, there are three things you need to do (but before you proceed, I must warn you – this becomes addictive):

  1. Get a bigger/better antenna. Antennas are measured by something called “gain”. The more gain, the better (generally speaking). More gain means the same signal is received stronger and with more clarity.
  2. Reduce the other noise. A bigger antenna will amplify all signals in the same frequency range. ADS-B is on a very specific frequency (1090 MHz). An ADS-B filter reduces the signal at frequencies other than 1090 MHz.
  3. Amplify the filtered signal. With the other signals filtered out, amplify what remains (legit 1090 MHz ADS-B signals).

This is what my full setup looks like:

Full ADS-B setup with 1090 MHz antenna, 1090 MHz filter, and Flightaware pro stick
Full ADS-B setup with 1090 MHz antenna, 1090 MHz filter, and Flightaware Pro stick

FlightAware started producing each of these a couple years ago (again, sticking with the theme of making it easy to provide them data). Originally, each was a separate item. Now the amplifier and filter are built into the same device on the FlightAware Pro Stick Plus. The antenna will remain separate. These upgrades together will cost around $80-90. I’ve provided some Amazon links below to check the current prices:

I like to keep the filter and receiver separate so if something goes wrong with either I can keep sending signals. As a side note, I am up to 735 days feeding FlightAware without interruption (two years and two days)!

flightaware connected for 735 days straight
flightaware connected for 735 days straight

The antenna is currently hanging in my garage which isn’t ideal but I still get signals from 100+ miles away consistently. I messed with a bunch of DIY antennas that I’ll post one day but settled on the FlightAware stuff because it works so well. I have the full setup of FlightAware antenna feeding the 1090 MHz SMA filter into the Pro Stick. When I lived in California this yielded 100-200 planes on busy days up to 200 miles away. This stuff is good fun, and as I warned above, it gets addictive. There is a physical limit though to how far you can receive signals, and that limit is around 250 miles for planes at 40,000 ft due to the curvature of the earth. Planes flying lower will fall off at closer distances.

Repositioning the antenna

I moved the antenna up a bit and am getting 20% more messages per second and distance – take a look here at Receiving aircraft ADS-B (position) signals – part 3 (antenna reposition)

Please let me know in the comments what you want to see about my setup! I will get around to making YouTube videos eventually to post because I know a lot of people like videos more than text but I want to do the text stuff first to get my thoughts together.

Austin’s Nerdy Things is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com.

Categories
ADS-B SDR

Receiving aircraft ADS-B (position) signals

If you came from the SDR (software defined radio) introduction post, you already have an idea of what these devices can do. If you came from somewhere else and want a brief introduction, head on over to SDRs (or how I pull radio signals out of the air).

The SDR topic that provides me the most entertainment is picking up aircraft ADS-B (Automatic Dependent Surveillance-Broadcast) position signals. As of 2020, all civilian aircraft in the United States are required to transmit their position continuously. I am not sure of the specifics but they are transmitted at least once per second, sometimes more with different messages. The idea is if every aircraft has both a ADS-B transmitter and receiver, there will be less crashes because the position of every nearby aircraft is known. There is also a Federal Aviation Administration (FAA) component where they will be able to better direct aircraft in the national airspace.

What this means for those of us here on the ground is we can be constantly receiving position data from planes flying in the air above us, or taxiing around airports around us.

Below is a screenshot of what the Denver airspace looks like during a typical Tuesday evening:

aircraft positions around enver
ADS-B positions on a Tuesday evening

There are 33 aircraft with data being received by my stations in the above screenshot, of which 25 are showing a location. Green colors are low altitude, blues are medium, and purple is high altitude. The farthest plane away from my house (station) is 100.9 nautical miles away, or 115 “normal” miles away. The highest altitude is actually being shared by two planes: N499RK and ICAO identifier A66618, both of which are business jets, at 45,000 ft. The lowest plane is N735CF at 6,700 ft, which is a training aircraft doing pattern work (repeated take offs and landings) at KBJC.

It is pretty straight-forward to get this data, assuming you have the right equipment. Most people get started with a Raspberry Pi. If you already have one, great! It is super easy to flash the SD card with Piaware, plug in your SDR, attach the antenna and start watching the positions stream in.

If you don’t have a Raspberry Pi, they’re pretty reasonably priced. The Raspberry Pi 4 is the newest version. Any size memory will work. Raspberry Pi 3 will also work! If you want some information on getting started with a Raspberry Pi, check out my Getting Started with a Raspberry Pi YouTube video.

The most basic setup will run you about $110 to get started. This includes a Raspberry Pi 3B+ starter kit (with SD card and everything needed to run the Pi) as well as a RTL-SDR with a basic antenna. You can check the current prices here on Amazon:

CanaKit Raspberry Pi 3 B+ Starter Kit (32 GB EVO+ Edition)

Nooelec NESDR Mini USB RTL-SDR RTL2832U & R820T Tuner for ADS-B

These are the exact items I used to get started and they’re still up and running. I repurposed the Nooelec SDR for around the house stuff because I got a different SDR for ADS-B reception. As I was testing these links, Amazon kindly reminded me how long ago I got into this hobby – more than five years ago!

nooelec RTL-SDR purchased from Amazon in 2016
nooelec RTL-SDR purchased from Amazon in 2016

This post got long quick so I’ll stop here for now. The two links are enough for everything you need to get started. I’ll continue with a part two for how to set everything up, as well as upgrades to increase reception.

Continued at Receiving aircraft ADS-B (position) signals – part 2!

Austin’s Nerdy Things is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com.

Categories
SDR

SDRs (or how I pull radio signals out of the air)

I figured I’ll be posting things based on how frequently I used them, at least to start. Eventually, I’d like to post based on your requests! Out of all the topics listed in the Introduction post, I use (or at least have various systems & automations using) SDRs to pull data out of radio signals the most frequently. In fact, most of what I have set up runs 24×7.

First off – what is a SDR? SDR stands for software defined radio. It means you can plug in one of these USB-based devices into your computer, and instantly be able to pull radio signals out of the air. Previously, like from whenever radio became a thing, until recently, radios were analog devices made up of resistors, transistors, and other things like that. They were bought tuned to a specific frequency and further, only listening to a certain type of signal on that specific frequency.

Software defined radio (SDR) changes all of that. It can be tuned to a wide range of frequencies and just passes along the data it gets to whatever program you use to decode the signals. Luckily for us, there are many open-source programs written by very smart people that already decode these signals!

This is the broad post for SDRs. I’ll write more posts for what I’m doing with the specifics. You may also see them called RTL-SDRs. RTL is the shortened name of the chipset (RealTek). There are other, more expensive SDRs not based on RealTek chipsets that can work better in some situations. For me, the $15-25 RTL SDRs do great. RTL-SDRs were originally intended to receive over-the-air TV signals. I’m sure they do fine with that but I’ve never tried to utilize them for their intended use.

Here are some of the things I’m doing with SDRs:

  1. ADS-B aircraft signal reception. As of the beginning of 2020, all civilian aircraft within US airspace must constantly broadcast their position. With a decently positioned antenna, these signals can be received up to 250 miles away from the aircraft! Link to part one of ADS-B reception.
  2. AMR – automated meter reading. Where I live, the electric and gas utility has meters installed at my house that broadcast their usage at least once a minute. I can receive these signals from my (and my neighbors!) meters and plot them to determine electricity/natural gas usage.
  3. Temperature sensor reading. You know those basic temperature sensor kits that most dads have sitting near the kitchen sink? The ones with a screen showing temperature/humidity inside and outside? Those are very easily decoded. I have one hanging outside and a few others around the house. They can also be placed in the freezer for advanced warning if a freezer goes out!

Some other thing I’m not currently doing but have thought about:

  1. Satellite reception for weather satellites (US GOES, Russian Meteor M2, and others). They transmit when overhead for the non-geosynchronous satellites and all the time for the geosynchronous satellites. The antenna required is quite a bit bigger than the around-the-house SDR stuff but still perfectly reasonable.
  2. General amateur radio reception
  3. Police radio scanning
  4. Aviation frequency reception

This post will be much better with pictures! I’ll add them soon.