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Guide to Software Defined Radio
- AWildC182 7y agoEven if you have no idea what you're doing, I very much recommend buying one of the RTL-SDR dongles on amazon for ~$20-30 and playing around. For the cost of a movie ticket, an afternoon messing with one will teach you a MASSIVE amount of stuff about how RF works.
- asdfman123 7y agoI tried to set up an SDR for my journalist girlfriend, and like the rest of you hackers, reading the manual, figuring stuff out and getting something working is usually pretty easy for me -- but there is a whole lot to software-defined radio.
- AWildC182 7y agoWhat were you having issues with? Usually the RTL-SDR + SDR# (sdr sharp) works without any config. Once you start to look at more expensive devices like the Lime mini things get weird though.
- asdfman123 7y agoIt was a physical device and I was setting it up to read the police scanners. I do have problems sitting too long with documentation, though, I'm sure if I more patiently worked through it I could have set it up.
- mlaretallack 7y agoStart with the spectrum analyser app, it is a nice way to see what transmissions are around. This leads to "what is that".....
- larrywright 7y agoSeconded. I was playing with mine last week and had it set up to read pager messages. Turns out that hospitals still use pagers heavily, and pager data is completely unencrypted.
- larrywright 7y agoAdding, just in case anyone wants to do this on their own: IANAL, but my understanding is that in the US it is not against the law to capture and decode these plain-text messages, but it is probably against the law to publish that information elsewhere or act on it in some way (an example from the link below was intercepting taxi service text messages in order to gain a business advantage for your own taxi business). Source: https://www.fcc.gov/consumers/guides/interception-and-divulgence-radio-communications https://www.fcc.gov/consumers/guides/interception-and-divulg... via https://www.reddit.com/r/RTLSDR/comments/4nhg7h/legalities_of_intercepting_pager_signals/ https://www.reddit.com/r/RTLSDR/comments/4nhg7h/legalities_o... The text messages that float about in the ether these days aren’t messages between individuals, they’re monitoring alerts (refrigeration systems, computers), and medical (doctors being paged, order to clean hospital rooms, calls for medical transport). That’s the case at least here in my medium-sized town in the US Midwest. It could be very different elsewhere.
- amatecha 7y agoOh yeah, this has actually been a bit of a controversy in Vancouver recently[0][1], including speculation that the problem may be national. Local hospitals have now removed diagnosis data from the transmissions, but apparently still broadcast everything else, including "patient name, age, gender marker, their attending doctor and room number" (as of Sept 2019)[2]. Vancouver Coastal Health claims they "have no information to suggest private patient information has been used in any malicious way", which is a very disingenuous statement to make, because there's no conceivable way for them to know who has received radio transmissions or made use of such data maliciously. To be frank, I find this pretty mind-blowing and it's disappointing that even in the face of press/public attention, it's not being remedied. [0] https://openprivacy.ca/blog/2019/09/09/open-privacy-discovers-vancouver-patient-medical-data-breach/ https://openprivacy.ca/blog/2019/09/09/open-privacy-discover... [1] https://www.ctvnews.ca/health/pager-systems-used-in-healthcare-could-be-exposing-patient-data-across-canada-1.4727129 https://www.ctvnews.ca/health/pager-systems-used-in-healthca... [2] https://openprivacy.ca/blog/2019/09/26/pager-breach-update/ https://openprivacy.ca/blog/2019/09/26/pager-breach-update/
- MuffinFlavored 7y agoCan't those only receive and not send?
- larrywright 7y agoThat’s correct.
- AWildC182 7y agoThere are some more expensive options that do but it's not recommended if you don't have a amateur radio license
- mokus 7y agoIf you have no idea what you’re doing, then you should not be transmitting. There’s plenty of good clean fun to be had on the receive side, though.
- penagwin 7y agoReceiving radio is perfectly fine and you aren't at risk of interfering with anyone. Transmiting is very "dangerous" if you don't know what you're doing, and likely illegal unless you're licensed (you're only allowed to broadcast on certain frequencies below certain power limits without a license, but you can still cause trouble). Tl;Dr Please do not experiment with transmitting if you don't know what you're doing.
- galangalalgol 7y agoDon't listen to the rule followers! There are no SDRs out there with enough power to be much of a nuisance to anyone. Do look up what the band is for. Do watch it for a few hours or days to confirm it is clear, but seriously if you don't interfere with anyone the FCC isnt paying you a visit. Even if you do insist on following the rules, just stick to ism bands. 315 ( key fobs) (2.5ghz wifi bluetooth) and one around 900. You can go full blast on any sdr and not get close to the half watt limit.
- galangalalgol 7y ago
- dariusj18 7y agoAny recommendation for one to buy?
- fpgaminer 7y agoJust hop on Amazon and search for rtl-sdr dongle. AFAIK they're all roughly the same since they're based off the same hardware; any with decent reviews should be fine. I think mine was a Nooelec brand or something; comes with the dongle and an telescoping antenna.
- beanaroo 7y agoI recommend getting one from here: https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/ https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/ Great hardware with driver/software compatibility
- larrywright 7y agoMy advice would be the same. These units are mostly built on the same parts, the big difference is build quality (metal dongle vs plastic) and what antenna comes bundled (antenna quality/size matters a lot for anything beyond just tinkering).
- syedkarim 7y agoIt's more than just build-quality. The actual RF design is very different. The RTL-SDR V3 dongle was purpose built to be an SDR device. Most of the generic plastic dongles were designed to watch broadcast television.
- squarefoot 7y ago+1 on this one: well built, optimized for small signal reception (TV dongles are not) therefore lower noise etc. bias tee for active antennas, metal case. Still at a good price. I have two of them and never regretted the purchase. One day I'l probably get a HackRF or something similar, although I'm still good with the rtl-sdr.com dongles. If they made a small one with enclosed upconverter to be put in my laptop bag to be carried when I take a trip in the mountains I'd get one immediately. I've tried one of those no-name Chinese little boxes with HF and V-U inputs but performance is inferior compared to the above dongle.
- nullwarp 7y agoyeah! I had picked one up a while ago to play with it and had some fun and stashed it away for a while. Well last week i was BBQing and the receiver end of my little remote temp monitor stopped working. Found rtl_433 that already is setup to read the output from the sender portion and in like 10 minutes had it graphed on grafana with alerts for temps!
- GuyPostington 7y agoCan you show this off? It sounds like something I need to have in my life. What TSDB did you use? What did your conversion from rtl_433 to a metric look like?
- nullwarp 7y agoIt was a bit hacky, i just had rtl_433 output the values as json, piped them into a mqtt topic and used node-red to inject the values in influxdb nothing fancy
- sillysaurusx 7y agoIf you set up a HackRF in Chicago, you can hear police dispatch. It's pretty nifty.
- miohtama 7y agoSir, you just received the most news.ycombinator.comish comment award of the year.
- beanaroo 7y agoI either had a terrible antenna, interference or reception at my apartment and so my dongle gathered dust for a few years until I camr across an Android SDR Touch app. Using a USB-OTG I could easily listen in on the go for cheap.
- Rerarom 7y agoIn what country is a movie ticket $20? That seems unusually expensive to me.
- AkshatM 7y agoThis is the price of a movie ticket in the United States, at least in California. Source: lived in LA and the Bay Area.
- addandsubtract 7y ago3D movies cost €15 and IMAX tickets cost €18 in Berlin
- mysterydip 7y agoAgreed! I picked one up and learned about ADSB protocol and usage, and now have a live view of the air traffic in my vicinity. Sure, I could use one of the websites that tracks that info, but there's something about viewing it on your own equipment.
- kitd 7y agoAIUI, those websites are only hackers like you crowdsourcing that info anyway.
- larrywright 7y agoI believe that’s correct. FlightRadar will actually give you a free pro membership if you run a receiver in your house (basically a Raspberry Pi, SDR dongle, and an antenna).
- larrywright 7y agoFun fact: Most of those sites filter out a subset of air traffic, notably military and anyone that pays to have their flight data suppressed (typically celebrities or other high profile people). If you run your own equipment you’ll see everything within range of your antenna. The one notable exception is https://www.adsbexchange.com/ https://www.adsbexchange.com/, which actually allows you to just show just military aircraft or just aircraft that have been tagged as interesting (typically planes owned by high profile people like Bill Gates, large corporations, or news and police helicopters). It’s kind of fun to zoom their map out to the continental US and put on the military filter. At any given moment there are a surprising number of military aircraft over the US.
- JKCalhoun 7y agoHackaday (the other hacker news?) just posted a link to this ready-to-go Raspbian distro pre-packed with SDR software for the Raspberry Pi: https://pisdr.luigifreitas.me https://pisdr.luigifreitas.me
- mindentropy 7y agoI lost complete interest in SDR due to the fact that antenna's are very important. I am ok with the tools etc but the fact that I cannot do anything with the antennas and the interference put me off.
- Sanzig 7y agoI mean... you could go buy or build an antenna appropriate for the signal you want to monitor? If you've got the space for it, a wideband discone like this one [1] out on the balcony and up on your roof paired with a wideband LNA from Mini-Circuits will give you acceptable reception from low VHF all the way up through S-band. Or, if you are looking for a specific frequency, build yourself a dipole of the correct length (it's really not hard). You can't cheat physics, you do in fact need the right antenna. I don't know what else to tell you. [1] https://www.diamondantenna.net/d3000n.html https://www.diamondantenna.net/d3000n.html
- MuffinFlavored 7y agoOne project I want to do with SDR is relay + amplify my car smart key so that I can open my car from 50 feet away (as opposed to needing to be right next to it) Is this possible?
- UI_at_80x24 7y agoTechnically: yes The tricky part is having your key-fob close enough to a transceiver that can then rebroadcast it's signal. Which would no doubt run afoul of broadcast regulations. Devices like the RTL-SDR work on as receive-only. I'd suggest checking out your local Amateur-Radio club to learn the laws, get a license, and have fun with projects like that.
- galangalalgol 7y agoKey fobs are at 315, an ism band, so 0.5w is fine for everyone. Some are actually at 433, mostly European stuff. Technically not an ism band in the US but if the fcc doesn't go after VW i doubt they will come after you. Unless you are stealing cars with it.
- galangalalgol 7y agoI'll add that there are no SDRs from ettus, lime, or hackrf that put out even .25w without a separate amp. So he won't break the limit by accident.
- MuffinFlavored 7y agoYardStick One: software-controlled antenna port power (max 50 mA at 3.3 V) Is this enough to broadcast a signal stronger than my car key? If not, what do I need to do to get a stronger antenna/more power?
- galangalalgol 7y ago0.055A * 3.3V ~ 0.180w. That is way louder than your key fob.
- iudqnolq 7y agoRachel Kroll (wrote The Bozo Hour making fun of incompetent sysadmins and management) created a web portal for an SDR in C. I found her blog posts in the project very interesting. > http://scanner.rachelbythebay.com/ http://scanner.rachelbythebay.com/
- JoblessWonder 7y agoWhen I was messing around with ADS-B stuff for work I found this website to be very helpful with lots of ideas/links for projects: https://www.rtl-sdr.com/ https://www.rtl-sdr.com/
- fpgaminer 7y agoMan, this seems like such a great resource; wish I had found it when I first got into SDR. I wrote a blog post about controlling ceiling fans using SDR (https://blog.hmac.io/2019/10/25/making-dumb-fans-smart-using-software-defined-radio.html https://blog.hmac.io/2019/10/25/making-dumb-fans-smart-using...), but I glossed over my initial struggles just getting up to speed with this stuff. All the concepts of SDR are straightforward and fairly intuitive, but it's the software stack and actually using the tools that's hard. The whole field is niche enough that you end up stubbing your toe with every step you take in that world. Googling around and trying to figure out where to even begin comes up with so many fragmented, unhelpful pieces of information. You either end up being pointed at Gnu Radio, which amounts to an incomprehensible behemoth for a newbie, or you find the numerous lighter weight pieces of software which aren't very clear on what exactly they're good for and are often unmaintained. Luckily my first project was rather simple; ceiling fan remotes don't exactly use the most advanced protocols. Once I found CubicSDR and fiddled around with it enough I was able to dump the radio signals to an audio file and just tease the rest out in Audacity. My blog post mostly covers the nightmare that was the TX side of things.
- xconverge 7y agoThis write up is a great introduction to what can be done and is nearly word for word what I have been through so far with SDR and amateur radio. Another super interesting thing I have done with my RTL-SDR is track NOAA and Meteor weather satellites and decode the images in realtime as they fly by overhead
- travbrack 7y agoThat’s amazing. Did that require any custom code?
- Eehoj2zaiph 7y agoI want to broadcast (unidirectional) UDP packets over the air on 2.4 GHz or 5 GHz at 3+ Mbit/s at maximum (legal) power. Is there a good way to do this with any current SDR hardware? Or is my best bet to ab(use) wifi cards for this purpose?
- defen 7y agoWhat does "broadcast UDP packets" mean? They'll need some sort of physical encoding; if wifi, why not use a wifi card? If not wifi...what are you trying to do by broadcasting UDP packets?
- Eehoj2zaiph 7y agoBroadcast meaning unidirectional, with support multiple receivers, and no association or acknowledgements required. Correct me if I'm wrong, but I don't believe there is a "broadcast mode" for wifi. So I'm asking if there is some SDR software/hardware combo that works well for this purpose, or if re-purposing wifi is the best option.
- int_19h 7y agoUDP requires some physical layer, which 802.11 provides. There are others, but in any case, you can't just "broadcast UDP" over the radio by itself.
- Eehoj2zaiph 7y agoYes, of course. Any suggestions on SDR-based hardware/software options?
- syedkarim 7y agoWe broadcast UDP over various satellite transponders. We have also done this over terrestrial links. We've done UDP file broadcasting over DVB-S/DVB-T/LoRa/FSK/etc with forward error correction in the client/receiver. Feel free to contact me. Email in my profile.
- CraigJPerry 7y agoPlug for the “universal radio hacker” open source tool. It made it absolutely childs play to reverse engineer a wireless thermometer signal which i now feed into a dynamo db table and present as a graph via alexa. My kamado joe is at the bottom of the garden and when i’m smoking or bbq’ing i can bring up the meat and the grill temps on any screen in the house. Fantastic.
- dfc 7y agoThere was a nice paper on it at woot18: https://www.usenix.org/node/220563 https://www.usenix.org/node/220563
- acd 7y agoThanks what a good link to SDR, the link feels like a Christmas present. SDRPlay is a good SDR receiver a step up from RTL-SDR for exploring the radio spectrum. Plus to exploring software defined radios there is a good community built around ham that one can join.
- shifto 7y agoI got a SDRplay some time ago from a co-worker. I haven't used it yet because of the behemoth that is SDR, but with this source I feel I can finally do something with it.
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- mobilemidget 7y agoOh great Xmas gift for myself, better receiver :-)
- squarefoot 7y agoThanks for posting, I didn't know about LuaRadio. After playing with some examples I noticed the weird behaviour of the gnuplot windows that get focused and refreshed (including decorations) at every sample so that beside wasting cpu power for unneeded drawing, it takes away focus from the shell where the program was invoked, making impossible for example to press ctrl+c to stop the program. I was forced at every test to ctrl+alt+f1 to a full screen console to kill the process. There's a nice Lua GUI project called TekUI which includes a basic graphing control that could be imported and extended to do the same without the need of an external dependency like gnuplot. http://tekui.neoscientists.org/screenshots.html (look at about half of the page) http://tekui.neoscientists.org/releases/ It's highly portable, a few years ago I managed to compile and use it on a A10 ARM processor board (Hackberry if memory serves).
- vsergeev 7y agoThanks, I'll take a look! New plotting sinks are easy to add and I really would like to migrate to something more stable. Gnuplot has been finicky with many people's setups, and it's been a real sore point. They seem to run best with the wxt output on Linux.
- zzo38computer 7y agoI have some other questions: 1. Can Usenet (and perhaps also Unusenet) be used with amateur radio? 2. Can received AM/FM broadcasts be used as a input for SoX? 3. Is time synchronization possible with software defined radio? 4. Can it be used with a RF cable (such as to connect to a VCR)?
- Enginerrrd 7y agoFor 1.) Yes, with caveats. No encryption would be allowed. Typical data transfer rates are abysmal so it wouldn't be great for transferring files. And it might get interesting legally if you do transfer a file with music. I believe that would be broadcasting music which isn't allowed. 2.) Haven't tried this specifically, but I'd say almost certainly yes. Gnuraduo is all about creating audio processing pipelines. 3.) Yes, almost definitely, though there might be some technical aspects to it depending on what you're trying to accomplish. 4.) Yes, but that would likely require extra unnecessary steps.
- zzo38computer 7y agoThe caveats you mention would probably be irrelevant with text newsgroups. However, what I am asking is if there are specific protocols for transferring Usenet articles with amateur radio, and how those protocols work.