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Communications

Software Defined Radio Site Closes (sdr.hu) 58

Posted by EditorDavid from the no-signal dept.
Long-time Slashdot reader Z00L00K writes: The site known in amateur radio for access to a plethora of SDR (Software Defined Radio) sites sdr.hu has now closed down. The SDR sites that exists all over the world are for listening in to primarily shortwave radio.

From the site:

I'd like to say a big thanks to everyone who joined my journey with this project!

I hope you had a good time listening on the site, and learnt some things about SDR. The purpose of this site was to provide a technological demonstration for amateur radio operators about Software Defined Radio, and I hope this goal has been reached. As this website was a one-person hobby project, with my tasks and responsibilities growing, and my focus moving to other projects at which I hope to make a greater positive impact, I'm unable to further develop SDR.hu and protect it from abuse.

Furthermore, I think this site has some good alternatives now. Nevertheless, in my opinion amateur radio receivers should be shared with strict access control in the future.
Archive.org shows versions of the site dating back to at least 2015. But now in an FAQ its operator says they don't have the capacity to "protect it from abuse."

Though one amateur radio news site has already shared an alternative for finding online SDRs.
This discussion has been archived. No new comments can be posted.

Software Defined Radio Site Closes More

Software Defined Radio Site Closes

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  • This is why (Score:1)

    by Anonymous Coward
    we can't have nice things.

    • I was about to post with this exact title, but yeah.

      I really wish we could decrease the surplus population [of idiots] in this world. Some people really don't need to exist.

  • amateur radio receivers should be shared with strict access control in the future

    What the hell does that even mean?

    • Re:The what? (Score:5, Interesting)

      by drinkypoo ( 153816 ) <drink@hyperlogos.org> on Saturday June 13, 2020 @10:57AM (#60179242) Homepage Journal

      It means they were given instructions to desist, and told what to say to us. Nobody makes a complete 180 on an issue of software and hardware freedom like that otherwise

      • "I am now, and forever, a fine and upstanding bootlicker. (Man, will you stop squeezing my balls so hard?)"

        For those who prefer the uncensored edition. This is about as authentic as forced confession before beheading jihadi videos.

      • Still makes no sense to me. Given instructions by whom to do what?

        • It was the first thing to catch my eye also. Doesn't make sense to me neither. It does sound like a forced statement though. Maybe SDR is a threat to the state/mafia in some fashion

        • Owner might of gotten a job at one of the big radio companies (Qualcomm, Icom, Uniden, Yaesu) due to the knowledge and education gained from playing with SDR and displayed on his website. Obviously that knowledge shouldnt be in the open, but utilized to maximize shareholder value.

      • Nobody makes a complete 180 on an issue of software and hardware freedom like that otherwise

        Sure they do, some people still have enough integrity to be able to change an opinion with new information present. Your comment is equally applied to anyone running a TOR exit node and the resulting pain caused by their support for software freedom causing them to abandon projects.

        When people provide a service as a hobby it is only a matter of time before they eventually do a 180 and shutdown. Hobbies change, interests change, and when they do any tolerance to anything which goes wrong is very low.

        I find y

        • "You must see conspiracy theories *everywhere*."

          Conspiracies are the norm, not the exception.

          That doesn't mean I believe every conspiracy theory to come along, but it does mean I consider whether a conspiracy best fits the available facts, and don't just assume that one can't be responsible for something.

          When it comes to SDR there's more reason for government to be involved than for many situations where they turned out to be responsible. Governments love secrecy, and SDR helps penetrate it.

          "When people pro

          • Conspiracies are the norm, not the exception.

            Only to a conspiracy theorist. Reality typically shows an easy and logical explanation. Oh except for the WTC, that was definitely bombed by the FBI.

      • It means they were given instructions to desist, and told what to say to us. Nobody makes a complete 180 on an issue of software and hardware freedom like that otherwise

        I am sorry, I am not versed in SDR, so I don't understand that. Could you give me an once of context/background info?

        • Re:The what? (Score:5, Interesting)

          by Mister Transistor ( 259842 ) on Saturday June 13, 2020 @02:42PM (#60179848) Journal

          Software Defined Radios are Radio Frequency (RF) Receivers, and sometimes Transmitters. They are generic "engines" and can be programmed to receive on nearly any radio frequency within their range and frequency spectrum.

          These radios convert and dump a block of RF energy spectrum down in frequency to DC-audio frequencies, then use DSP technology to pick out the radio modulations of the RF signals they have captured. They can grab a wide swath (some as great as 20 MHz of spectrum) and decode EVERYTHING in that block of frequencies. This makes them especially good at things like scanning, radio astronomy, etc. where the exact frequencies, etc. are likely unknown and a large block of spectrum can be examined and decoded all at once.

          The first implementation of SDR were $1000.00 and up laboratory units that were usually based on a custom FPGA type of DSP IC at their core, and all the magic is in the software that runs them.

          The latest generation of SDR radios are sold in the form of DVB-TV dongles. These are USB dongles, sold everywhere on eBay, Amazon, etc. Some popular brands are Nooelec, Terratec and MANY others. These are sold for the AMAZING price of $15-20 or so, and usually come in a kit with a small telescopic antenna.
          They were designed for digital TV reception in Europe. DVB takes twice the bandwidth of HDTV that we use in the USA, so the DVB dongles do about 2.5 MHz of spectrum at one grab. One to do HDTV would require about 6 MHz of spectrum width. Anyway, these dongles have a "hidden" internal mode that makes them work as a general purpose radio receiver, and in that mode they are used as a generic SDR engine.

          So, for $20.00 and some nice free software (there are LOTS of programs out there for them), you can get on the air, to receive. Transmitting still costs a bit more, dongles that are more specific to SDR and that have low-power transmitters in them cost a bit more, like $75-100 or so.

          There are lots of other good SDR sites out there, my favorite is RTL-SDR.com, great stuff. I was not a regular at this site but I do remember having visited there before.

          As far as control goes, they are receivers, for the most part. Receivers are usually not regulated, except in countries where the govt. doesn't want citizens tuning in some particular radio broadcasts. Most nations/states/agencies now use encryption to prevent the wanton crime of radio reception. Transmitters are another matter, they are usually strictly controlled to prevent mis-use and spectrum pollution, but mostly, receivers are not.
          This definitely sounds fishy, like "strict controls" on encryption. Yes, I do think SDR will become a target of freedom-restricting regimes and governments, just like encryption has.

    • In many parts of the world listening to specific frequencies or broadcasts is illegal. My guess is the government made him an offer he couldn't refuse. Today a $10 USB dongle has the receiving capabilities of hardware that used to cost thousands of dollars. Now that trunking radio is popular with the cops its trivial to get two dongles and have one receive the control channel and the other receive the broadcasts. Of course the radios use P25 encryption depending on the agency.

      I looked to see if there was an

      • In many parts of the world listening to specific frequencies or broadcasts is illegal. My guess is the government made him an offer he couldn't refuse.

        He isn't in many parts of the world. He is in Belgium and no it's not illegal to listen to open broadcasts there.

      • 1) That doesn't explain what "strict access control" the owner of such a site could possibly implement to make that legal. If it's not legal in the first place, you can't circumvent that by allowing just a circle of friends to access it.

        2) Nobody forces an SDR site operator to give anyone access to restricted frequency bands or modes of operation. Or not? It's up to every such individual operator to consider local legislation. Amateur bands at the very least are unrestricted for reception outside of dictato

    • There needs to be more folks objecting to any limits on receiving radio, regardless of which tyrant run country, or tyrant run army, or tyrant inspired agency or bureaucracy in an otherwise democratic country wants it otherwise. Those more vicious manifestations of humanity can figure out how to encrypt their communications if it really matters to them. It shouldn't be a problem for anyone in the public, or amateur radio licensee, in particular, to worry about what kind of receiver or receiving process

  • Here's an idea... (Score:4, Interesting)

    by beheaderaswp ( 549877 ) * on Saturday June 13, 2020 @11:42AM (#60179348)

    My perspective on this as a license holder goes like this:

    If you run an internet facing service you are constantly be probed and tested by nefarious network activity. This becomes a real pain in the ass if your primary interest is not in networking.

    The other issue is the legality. There are frequencies that are illegal for the general public to monitor. In most places Amateur Radio operators are exempted from those regulations. However with impending(?) changes in internet law this person could be considered responsible for someone listening illegally to a particular transmission.

    Alternative services, like remotehams.com, will allow unlicensed users on their systems- assuming the radio owner allows it. The radio owner also sets permissions for use based on an unlicensed status or license class and is ultimately responsible for the use of the system. This includes transmit rights. And a large number of these systems are excellent SDR systems that far surpass the "LimeSDR" type systems.

    http://rx.linkfanel.net/ [linkfanel.net] is also a very good alternative.

    This is the snapshot of what this guy is probably seeing.

  • Virtually all communications are done through radio waves at some point. And an SDR can passively listen in on all within range. Phone calls, military communications, satellites, virtually the whole of human communication now goes through the air and with the right configuration and location, an SDR can listen in.

    That is probably why, with some government prodding, the site is shutting down. There are probably a heavy emphasis in the community on spying which was attracting a lot of negative attention.

    W

  • SDR is interesting, however: (Score:4, Insightful)

    by Rick Schumann ( 4662797 ) on Saturday June 13, 2020 @01:41PM (#60179678) Journal

    Coil of wire
    Air-variable capacitor
    Detector diode (germanium, like 1N34A works well)
    Filter capacitor (0.01uF is good)
    Crystal earphone or 2000-ohm headphones
    Antenna
    Earth ground (optional)

    That's all you need to make an AM radio receiver.
    Wind the coil for different inductance, use a different air-variable capacitor, you change what range of wavelengths it can receive.

    I'm not dumping on software-defined radio; it's an amazing technology. What I am saying is that RF electronics is still a Thing, although it's apparently becoming a Lost Art. You can build amazinging sensitive and selective receivers using nothing but discrete components; I've still got around somewhere some very, very old books full of simple receiver designs that anyone with moderate skill can build. No FPGAs or DSPs required, no Masters or PhD-level programming skills required, just some basic hand tools and a soldering iron. Imagine that! xD

    Would also like to point out: that's just receivers. You want to build a transmitter? You can't do that with just digital electronics. You need analog, RF electronics for that, an oscillator, tuned circuits, RF power-handling, and a properly-tuned antenna.

    Of course someone is likely to chime in now and say that you can just go buy whatever receivers/transmitters/transceivers you want, off-the-shelf. But that's not my point at all.
    My point is: 'newer' and 'more complex' isn't necessarily 'better'. Price and complexity can be a barrier to many people. You can accomplish quite a bit with a handful of components that cost only as much as a few dollars apiece, and in my never-to-be-quite-humble opinion, it's worth the effort. :-)

    • Re: (Score:3)

      by dougmc ( 70836 )

      Would also like to point out: that's just receivers. You want to build a transmitter? You can't do that with just digital electronics. You need analog, RF electronics for that, an oscillator, tuned circuits, RF power-handling, and a properly-tuned antenna.

      That's kind of an odd distinction.

      I mean, even the receivers require "analog, RF electronics" too -- even your crystal radio is full of them. Sure, they can mostly be put into an IC, but that's true for a transmitter too. And receivers for anything more complicated than an AM crystal radio typically have oscillators, tuned circuits, etc. too. Even a CW or SSB receiver typically has these things, for example [qsl.net].

      (I should also mention that even your crystal radio has a tuned circuit -- I mean, that's exactly

      • I know SDR still requires an analog, RF front-end, I did skip over that fact, but in the case of SDR it's minimalistic compared to a full-blown superheterodyne receiver.
        A 'properly tuned antenna' is necessary for a transmitter for it's final amp to not burn itself to a crisp (or melt it's plate, in the case of vacuum tubes), but it's also helpful for receiving, just not as vital.
        Analog being a lost art, not so much?
        I've talked to some 'young guys' online that were certain, absolutely certain, that you n

      • Re: (Score:2)

        by tlhIngan ( 30335 )

        It's the same arguments over again.

        Let's say you want to blink an LED. There are dozens of options, including special LEDs you can buy that blink.

        But the common ways are:

        1) Use a simple astable multivibrator (aka, oscillator) circuit
        2) Use the 555
        3) Use a microcontroller and some firmware to blink an LED.

        1 and 2 are plainly obvious to anyone with a history in electronics, but 3 is likely a cheaper, quicker and more flexible option (face it - chinese microcontrollers are cheap when you can buy them for 3 cen

    • Re: (Score:2)

      by hjf ( 703092 )

      Good luck finding germanium diodes or high impedance headphones

      • Re: (Score:3)

        by jiriw ( 444695 )

        I just bought 200 germanium diodes in China. Use them for a simple 3-transistor signal detector. Great introduction to soldering hobby project for a group of primary school kids, for example. (It makes all kinds of crazy sounds when you hold it near modern equipment, especially switched power supplies. Total BOM price including a PCB.... a couple of dollars) Yes, they work fine. Yes, they were less than 5 cents each.

        https://www.ebay.com/itm/100PCS-GERMANIUM-DIODE-1N34A-DO-35-1N34-IN34A-NEW/202410514882

        73, P

        • *nodding* yep. I think any schoolkid should build something like that at some point. In the age of cheap fast computers and smartphones, imagine their faces when a few simple discrete components produces the programs from any AM radio station in range? Some would think it's some sort of trick! xD

      • Re: (Score:2)

        by Ozoner ( 1406169 )

        Germanium diodes are readily available, and there are many alternatives such as Schottky diodes or FET detectors.

        To convert a low impedance phone, simply use a high impedance transformer. Or use use a Crystal Earpiece or a piezo buzzer.

        • *nodding* yep a piezo buzzer-speaker would probably work. Be a little tinny though and not very loud; glue it to a piece of paper or thin cardboard?
      • I think an 1N60 will work, too. That's just what was at the top of my head. There's other diodes you can use. I think a Schottky diode would work, it's got a low enough junction voltage. I've also seen biased junction crystal receivers, and if you want to get a little more fancy, you can use a JFET or maybe even a MOSFET, but then you'll need a power source (a AAA battery would be enough, really). xD
        I think somewhere out there you could find crystal earphones or headphones. Or, if you don't mind adding ano

    • Re: (Score:2)

      by jiriw ( 444695 )

      Or you take a Raspberry Pi and do some apt-getting to install a piece of software. Solder a wire to one of the GPIO pins and away you go polluting at all higher harmonic frequencies... You at least need that piece of wire for your receiver as well. What's an antenna if not a piece of analog equipment?
      But you said, build a transmitter. You didn't specify power output and cleanness of signal. But then again ... ethernet over powerline adapters aren't that more sophisticated either, so who cares? Unless your h

      • You and I both know that the simplest transmitter is just an oscillator with the simplest of AM modulators and the right antenna. Can be done with 1 transistor so far as I remember, am I right?

    • You can't do that with just digital electronics.

      Direct synthesis SDR doesn't count?

      • You still need some RF components for power handling if nothing else, and you need some tuned circuit(s) as well. Something like Bluetooth doesn't really count, if you were going to say that, because that's so low-power, but even then you still need at least an antenna of the proper wavelength, even if it's just synthesized as traces on a PCB (which you can certainly do). But if you want to transmit a signal miles and miles or hundreds or thousands of miles away you need some real RF circuitry.
  • "in my opinion amateur radio receivers should be shared with strict access control in the future." what the fuck? I must be missing some context because that sounds like a crock of shit. smells like it too

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