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Comment by atonse | Hacker News Reader

SDR is one of those technologies I still want to play with that I feel will open up this incredible new world to my curious mind. All of a sudden, the invisible waves around us that we often tangentially know about but never think about (because we can't see, smell, or hear them), become a whole sixth sense to explore.

I really hope for some free time to play with this, and to expose this invisible world to those around me (especially my kids), in a way that has been much less accessible in the past.

Even things like ceiling fan remotes, door sensors, wifi, a garage remote, a car key, ISS video feeds, data from stuff in SPACE, weather data, I mean, we're bombarded with it every day all the time and we just don't realize it.

Anyway, just had a wide-eyed moment, as I do every time I read about another thing that makes SDR just a bit easier to access.

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The best one is the ADS-B Out from airplanes, you can map the planes around you with a $20 widget.

This sounds really cool. When you say 'around you', what kind of radius are we talking?

Hard to answer that it depends on so much; the quality of the rx you're using, the antenna and your local environment (open field? wooded area? valley? top of a hill?).

It really depends on the environment around you. I live deep in valley, so my range is pretty limited to line of sight.

You may be able to find out more information, including instructions on assembling your own ground station, at Flightaware - https://flightaware.com/adsb/piaware/build/

As others have said, it depends on terrain, your antenna, the altitude of the aircraft, etc. But generally, 50-60 miles is pretty easy with almost any setup.

I have an ADS-B antenna mounted on my roof that feeds into a filter and an amp, and I get less than 50 miles in some directions (because of mountains) and more than 150 miles in other directions (over the ocean).

Here's a map of my coverage (any altitude), with range rings every 50 miles: https://www.flickr.com/photos/wallofhair/51403416502

My coverage for altitudes up to 10,000 feet: https://www.flickr.com/photos/wallofhair/51404165241

It's radio, so nothing's guaranteed. Those maps show the maximum ranges at which I picked up any aircraft in that direction over a couple months, so they're kind of a best-case, showing when conditions possibly happened to be perfect. I also have a dead zone just around my house, because my gain is configured to prioritize range. Lots of tradeoffs in RF.

There's a site (with an impossible-to-remember name) that can predict antenna range for you (it's not obvious how to use it; Try "New panorama", then "Up in the Air"): http://www.heywhatsthat.com/

Here's what it shows for me. The blue ring is 40,000 feet altitude and the orange ring is 10,000 feet altitude: https://www.flickr.com/photos/wallofhair/51404944889

How do you get that footprint plot? I'm using dump1090-fa and don't see it

To answer my own question, in case others are interested: https://discussions.flightaware.com/t/how-do-you-create-a-co...

It depends on your location, antenna, and the aircraft's elevation, but in the bay area I'll often pick up aircraft all the way out to Sacramento. Sometimes quite a bit further.

Of course, the higher the aircraft the further you can "see" them. Most of the traffic I see is within 45 miles (especially low flying GA traffic), but I'll still pick up the occasional high altitude aircraft at 100+ miles out.

It’s very fun! I use it to monitor for low flying aircraft around a farm where I am doing some drone experiments. The legal drone limit in my area is 400 feet above ground level and near the hills some aircraft fly pretty low, so I’m going to ground the drone any time an aircraft is nearby that is not above 10kft.

I highly recommend not relying on SDR ADS-B reception alone and also checking online data systems for ADS-B that also use multilateration to track aircraft using their transponder when they aren’t ADS-B capable. Otherwise you might be operating under the assumption there are no contacts in your working airspace when there is aircraft present but not announcing their location.

https://flightaware.com/adsb/mlat/

You need both data sources—a number of planes are “delisted” from the commercial trackers and won’t show up, but they still broadcast ADS-B. You can find partial lists of such registrations through a keen Google search.

https://www.adsbexchange.com/ does not blacklist or delist aircraft tail numbers fwiw.

Sounds like a good idea. Thanks for the suggestion.

Hope it helps.

160 miles with a £6 rtlsdr and an antenna I bodged out of coax. Its painfully easy. Also have a nosy at POCSAG - there's still a little bit left in the UK.

Similarly you can map out lightning strikes with similar tools/methods.

Can you provide some resources about this?

There is the Blitzortung.org site - https://www.blitzortung.org/en/cover_your_area.php - which has some interesting information.

Thanks, but that link appears to be about dedicated modules. I already have a HackRF One and an RSPDuo, the person I was replying to seems to indicate it was possible to use a typical SDR.

If you want to play without spending too much money or time, yo always can get a chinese DVB-T USB receiver or similar with a RTL chip. It cost less than 50 bucks and usually works well without too much configuration AFAIK. Don't expect an incredible SNR or wideband, but it's pretty good for tinkering.

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