9 ms·
Mystery signal from a helicopter
- mablae 13y agogithub?
- GauntletWizard 13y agoNice bit of reverse-engineering, and an impressive hack from whoever built the system.
- jrockway 13y agoNot really a hack. Subcarriers are how they added color to TV, stereo to FM radio, and so on. WWV/WWVH also sends machine-readable time codes at 100Hz like this.
- jzwinck 13y agoIndeed--it was more of a hack sixty years ago perhaps. Since then, similar tricks have been used for closed captions, Dolby surround (the original kind), Radio Data System (which puts song names on your car dashboard via FM radio), TV Second Audio Program (listen to shows dubbed in a second language, just press the SAP button on your ancient high-end TV!)....
- jahmed 13y agoWow. I always thought SAP stood for Spanish Audio Program. TIL.
- EEGuy 13y ago>Subcarriers are how they added [...] stereo to FM radio... Set your time machine for 1958, or follow this link [0] to see how RCA did both FM stereo (throughout the article they call it "multiplex") and 67 KHz "SCA" subcarriers. Admire the awesome 5KW FM transmitter cabinetry and transformer shielding. [0] http://fmamradios.com/BTE-10B.html http://fmamradios.com/BTE-10B.html
- jrockway 13y agoOne thing I find particularly interesting about articles from this time period is that Hz is not yet the name for 1/s, and so everything is in "cycles per second". According to Wikipedia, the transition started in 1960, so we're two years away when this article was published.
- the-kenny 13y agoQuite funny - I know someone who uses a similar setup to send GPS Coordinates for a Quadcopter and a Plane via the audio channel of the video link (he flies the Quadcopter/Plane with video goggles) to the ground station. There, an Arduino controls some stepper motors to point directional antennas at the copter/plane. Project is at https://github.com/KipK/Ghettostation https://github.com/KipK/Ghettostation - video at https://www.youtube.com/watch?v=tiO4YCX7hJo https://www.youtube.com/watch?v=tiO4YCX7hJo - you can hear the modulation in https://www.youtube.com/watch?v=nm0okv8mTsg https://www.youtube.com/watch?v=nm0okv8mTsg
- bri3d 13y agoCool! I hadn't seen that project before, although I'd seen a few other telemetry-over-audio solutions. They usually use simple FSK just like the "real life" helicopter in the article. Here's an example of a common simple protocol: http://www.flytron.com/pdf/audio_modem.pdf http://www.flytron.com/pdf/audio_modem.pdf
- anigbrowl 13y agoUsing spare audio capacity like this is actually very common - prior to digital recording, engineers would dedicate one tape channel to recording a sync signal, and in mission-critical applications would even 'stripe' the tape with the sync signal beforehand (many pro recorders can have recording and read heads active simultaneously).
- amcnett 13y agoIt'd be interesting to scrape videos for this kind of information in order to map them en-masse. Great post!
- werner34 13y agoOona's work is always amazing. Loads of interesting hardware stuff in her blog. I wish I would be better at some mechanical engineering/electrical engineering stuff, my work is mostly web-related or big data stuff, never really get my hands dirty :(
- NamTaf 13y agoYou can basically reverse those terms for me. I'm a mech engineer who wished he knew more/was better at the web-dev / big data stuff.
- hiharryhere 13y agoSounds like you guys should be friends.
- lifeisstillgood 13y agoSounds like if they ever met, big explosion !
- throwwit 13y agoI wonder how much audio compression the signal can go through before getting lost, and if joint-stereo affected it. Might have to check out the data myself :) Props to Oona.
- sethhochberg 13y agoGiven that most audio compression techniques are perceptual, and the signal here falls into the "most important" 300hz to 3.4khz range that gets special attention in human hearing, I'd guess it is pretty resilient to run of the mill compressed audio codecs.
- rikacomet 13y agocan this become/or is/ part of forensic science? if its possible to do the same on a mobile phone, and merely speaking into the phone, you give away your travel trajectory?
- nwh 13y agoNo, in this case it was intentionally encoded in the audio.
- _nedR 13y agoThey're way ahead of you :- They can take any audio recording (from any source) in the UK and get an exact time-stamp of its recording and detect whether it has been edited in any way : http://www.bbc.co.uk/news/science-environment-20629671 http://www.bbc.co.uk/news/science-environment-20629671
- TempleOSV2 13y agopastimes leaven afraid measure enemy from revolting approached flagon sons virginity notice surmounted rebel threefold nets succeeding terrible OTHER admittest estimation turbulent servant's imperfect silence containing heart decree electronically acuteness print preparest enjoined namely unutterable caresses frightful Mammon heaven steered congratulating Great tumultuous attentive hearken rescuing got momentous exacted gentleness hopeful AM consists beams aged -unto crudities expects breast marrying disposed senator's whit elevation sentences or instructest food draught metre upon stated instability gainsay physician scraped foreigner talkers arithmetic true-speaking filling meanings foully calledst Be caves stupidity obedient helping draws openest clasped year before follows stirred modesty anonymous sanctity thirsted anxiously i ranged opinion THE wedlock meditate sacrificed fall resist setting outset four-footed other's roused spake Ignorant dumb Interrupt anointings teaches apostle Jordan gladdened persuasions suffered shared settled alloy audience feverishness lust probable uncertainties imbibe stones sparedst females incredible bridegroom shut everywhere weaving likely mistress abundance nurse ear dumb bestowedst desirous suitable scratching true-speaking blunt Sudden prayer incensed worshipper reverently came propoundest deep redemption death-bringing
- zenocon 13y agoThis is the kind of article that makes HN worth coming back for.
- jgrahamc 13y agoI love Oona Räisänen's blog. She's my hero. She combines a love of figuring stuff out with lots of fun hacks. And when I read her blog it makes me happy to see someone with that joy of uncovering mysteries.
- tezmc 13y agoYou've probably already seen it, but in case you haven't: her talk at 30C3 was excellent and is worth a watch. https://www.youtube.com/watch?v=R-2k6TMPMRo https://www.youtube.com/watch?v=R-2k6TMPMRo
- lucb1e 13y agoBeen there, was cool indeed! If you aren't planning to already, you should come to the 31c3 :)
- sitkack 13y agoIt is a certain commitment to Germany over Christmas.
- lucb1e 13y agoIt started the day after Christmas, though I did travel on second Christmas day. Totally worth it in my opinion. This was my first year and I can say that an extra day of that experience is always worth it. Also WiFi totally rocked on day -1, but if you want that I guess you could also go wired any other day (symmetric gigabit and the best abuse policy in the world yay!). But of course you can also travel on the day it starts and miss a few talks, it's up to you and your family how much of an issue it is to miss 2nd Christmas day. I was home in plenty of time for new year though, you still have that ;)
- sitkack 13y agoThat and Hamburg is a beautiful town.
- lucb1e 13y agoAnd here I always consider myself paranoid when wondering whether odd patterns in anything mean anything. Guess I'm just too noob and inpersistent to find anything.
- quackerhacker 13y agoAmazing!!! I would have just dismissed it as static interference, and not even think twice. Hmmm, makes me think twice about the beeping sounds I hear when my phone is right next to my radio. I know it's data being transmitted/received, but I wonder if it can be deciphered in this manner.
- anigbrowl 13y agoIt's the phone checking in with the base station. As someone who records sound for a living, this is one of the banes of my professional life - I tell people on film sets to turn their phones off, and they think I mean 'don't use your phone' whereas in fact I mean 'shut it down completely.'
- seer 13y agoShe already did that :) http://www.windytan.com/2013/01/the-gsm-buzz.html http://www.windytan.com/2013/01/the-gsm-buzz.html
- nolite 13y agowow.. this girl is superhuman...
- fellytone84 13y agoCan someone explain how she plotted the car's position? Did she manually reconstruct it based on the video and the information she derived from the helicopter's noise?
- maxerickson 13y agoI think so. It isn't a big deal to find the tennis courts in the beginning of the video: https://maps.google.com/maps?ll=39.04082,-94.560871&t=h https://maps.google.com/maps?ll=39.04082,-94.560871&t=h I did that using her plots, but working backwards from the city hall to the freeway would only be tedious, not impossible.
- codr 13y agothis is rad.
- salgernon 13y agoI'd had a copy of her dialup decoded poster on my wall for a while; forgot where I found it but it was immediately something I wanted to hang up... glad to see its being monetized via poster sales, its quite a lovely work of art. Of course, I also find chip tape outs beautiful, much to my wife's dismay. http://vlsiweb.stanford.edu/~jaeha/chip_gallery.html
- hodgesmr 13y agoIt's sold here: http://www.redbubble.com/people/windytan/works/9934517-the-sound-of-the-dialup-explained http://www.redbubble.com/people/windytan/works/9934517-the-s...
- cdelsolar 13y agoamazing!
- mangeletti 13y agoAnyone else see the cop hit him @ https://www.youtube.com/watch?v=TCKRe4jJ0Qk#t=1140 https://www.youtube.com/watch?v=TCKRe4jJ0Qk#t=1140 (19min)?
- sehugg 13y agoAnother cool thing is that the author of Redis made a decoder for ADS-B to decode aircraft transponder signals: https://github.com/antirez/dump1090 https://github.com/antirez/dump1090
- nl 13y agoI love this: Several people in the restaurant were waiting for orders with their similar devices, which suggested to me this could be a pager system of some sort. Turning the receiver over, we see stickers with interesting information, including a UHF carrier frequency. For this kind of situations I often carry my RTL2832U-based television receiver dongle with me (the so-called rtl-sdr). I knew I was forgetting something. http://www.windytan.com/2013/09/the-burger-pager.html http://www.windytan.com/2013/09/the-burger-pager.html
- sown 13y agohttp://www.oz9aec.net/index.php/gnu-radio/gnu-radio-blog/464-rtl2832u-based-software-defined-radios http://www.oz9aec.net/index.php/gnu-radio/gnu-radio-blog/464... I think this is what she was talking about? Note to self: buy one! :D
- sharpneli 13y agohttp://www.amazon.com/NooElec-RTL-SDR-RTL2832U-Software-Packages/dp/B008S7AVTC http://www.amazon.com/NooElec-RTL-SDR-RTL2832U-Software-Pack... It's so cheap it's practically free (I mean come on, 3.2MHz BW for that price?). The included antenna is horrible but it suffices for small things like finding out something about the restaurant buzzers. Oona is doing an extremely important service for Ham radio communities etc. She is bringing the knowledge of all of this to a wider audience on the internet.
- wglb 13y agoFor this kind of situations I often carry my RTL2832U-based television receiver dongle with me But of course.
- dsuth 13y agoAs you would, really.
- TeMPOraL 13y agoI've seen similar devices in a pizza joint. Does anyone know why they are so big and ugly?
- sown 13y agoI need to learn HW. Could someone detail more information about the tools she used?
- habosa 13y agoWow. People on HN do a lot of cool things but that really blew me away. It all sounded so casual too. This is real Hacker News.
- atourgates 13y agoIf I'd seen this recreated in an episode of CSI, I would have thought "Bullshit."
- toomuchtodo 13y agoEnhance!
- cgate 13y agoYup, I guess there is little overlap between the CS community and electronics community.
- TeMPOraL 13y agoAlso, surprisingly, after being exposed to things like this over and over again, people in CS community still underestimate the capabilities of technology.
- vhost- 13y agoThe thing I love most about her work is it's witty, but to the point and I can always understand it. I'm not a big fan of the tl;dr movement, but I also don't like dauntingly long blog posts. Nails it every time. Hats off!
- DonGateley 13y agoWhat is the tl;dr movement?
- coldtea 13y agoHe means people complaining that a post is too long and so they won't read it.
- inanov 13y agohackers rule!
- logicallee 13y agoI didn't get how she can get so much sense out of what is basically line noise - until the comment that asked what tools she uses, and she says Perl. Ah, just a day in the life :)
- c7b0rg 13y agoSuddenly, my telecom courses in CS now seem a lot more fun than they really were. It's like magic.
- xradionut 13y agoWhile I love the blog and the very clear explanations, none of this is new nor amazing to the experienced RF engineer, enthusiast, or practitioner. What's awesome is that the hardware and software are currently cheap enough that more people can discover and enjoy the larger spectrum around them. Welcome! Now go build some antennas! :)
- sebastianconcpt 13y agoJaw-dropping
- graupel 13y agoWe operate news helicopters at TV stations around the US and they all use a similar system. Basically the right channel of audio is typically the microphone from the pilot or reporter and the left channel is the audio feed transmitting what is basically modem data back with the GPS coordinates of the helicopter and some other data. This data is used at the antenna site to track the helicopter and point the antenna in the correct direction to keep a line-of-site since the transmission system from the helicopter to the receiver is line of site (microwave) based. It's really cool to sit and watch the receive antenna track and move responding to the movements of the helicopter miles and miles away. The antenna is on the belly of the chopper here - http://www.imt-broadcast.com/super-pod?cat=Products http://www.imt-broadcast.com/super-pod?cat=Products The receiver is generally centrally located on a tower - http://www.imt-broadcast.com/silhouette?cat=Products http://www.imt-broadcast.com/silhouette?cat=Products - it's a parabolic dish inside a radome like this.
- toomuchtodo 13y agoHow do you ensure that the receiver on the tower always has LOS to the mobile unit? I can't imagine its on a track to have full 360 degrees of motion around the tower.
- graupel 13y agoSay you have the receiver on the top of a downtown building or a tower and you are transmitting from 1500', there's not too much that can get in the LOS. Receive systems can either be a single antenna, a series of antennas, or (like in the link above) a dish inside a radome - the dish generally can rotate the full 360 since the cable slips through the middle.
- unwind 13y agoI'm not a native speaker, but still have a pet peeve for that one. It's "line-of-sight" (http://en.wikipedia.org/wiki/Line-of-sight http://en.wikipedia.org/wiki/Line-of-sight). Light travels in a straight line over (human-scale) long distances, so you need a straight line free from obstruction to see between two points. I'm sure you know this and just made a typo, of course. Thanks for the additional information about this interesting solution.
- easy_rider 13y agoCan anyone recommend some cheap hardware to hookup my TG-UV2 [1] to my PC? [1]http://www.eham.net/reviews/detail/8931 http://www.eham.net/reviews/detail/8931
- ErsatzVerkehr 13y agoI would love to try a "signals hacking" capture-the-flag.
- niels 13y agoThis is also commonly used on Model Planes flying "First Person View". See http://www.youtube.com/watch?v=A_AnqOFAs3Q http://www.youtube.com/watch?v=A_AnqOFAs3Q for an example.
- tomchurchill 13y agoThe Kansas City Police helicopters are also equipped with 3 of our Augmented Reality mapping Systems: http://www.churchillnavigation.com/media/videos/40-san-juan-county-sheriffs-ars-system http://www.churchillnavigation.com/media/videos/40-san-juan-...
- hans 13y agocool thing is, we can start watching them back ;/ and critique whether they're joy riding or actually working etc
- rubysucks 13y agoGet a job, I wish I could sit around analyzing YouTube clips for 8 hours a day.
- atmosx 13y agoException profile and work. I never seen anything similar and never really thought that this was possible. Really stunned :-)