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A $20 Software Defined Radio For GNU Radio

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  • Going up... (Score:5, Insightful)

    by pushing-robot (1037830) on Wednesday September 19, 2012 @09:49AM (#41386279)

    Wow, inflation is really hitting these things...

    http://hardware.slashdot.org/story/12/03/31/1914217/software-defined-radio-for-11 [slashdot.org]

    • Re:Going up... (Score:4, Informative)

      by Anonymous Coward on Wednesday September 19, 2012 @10:04AM (#41386469)

      These super-cheap little dongles are *terrible* performers. They suffer from de-sense when nearby strong stations transmit, tend to have I/Q balance problems, and so on.

      You want good performance from an SDR, you're not going to get it for $20. Providing the dynamic range you need to prevent desense and intermod isn't that easy, nor is providing the sample rate you need to deal with a broad swatch of the receive spectrum at one time at the same time you keep that dynamic range.

      The cost will be several times that (at least.) And there are units on the market (See RFSPACE) that are hundreds of dollars and even over a thousand, but oh, man, once you use one, you'll know why. I have an SDR-IQ (and write free support software for SDRs, including that one) and I live and breathe these things on a day to day basis.

      • Re:Going up... (Score:4, Insightful)

        by BLKMGK (34057) <morejunk4me&hotmail,com> on Wednesday September 19, 2012 @10:17AM (#41386621) Homepage Journal

        Limitations aside, cheap hardware lets people get their hands dirty and understand the software. I am pretty ignorant of this stuff but interested in it. $20 is peanuts and having software explained for it is helpful. Perhaps users playing with the cheap stuff will become interested in it enough to spring for more expensive gear? As it stands now I wouldn't spend hundreds (I want to build other things too!) on an SDR I might not get much use out of but $20 is certainly doable.

        What seems strange to me is that these TV tuners are out there cheap with all of this bandwidth but no one seems to build more dedicated tuners just for hacking around using the same stuff. Surely if someone knew what they were doing they could design something from these and sell it cheap for people to play with? Could they perhaps make some cheap design decisions that would make them more useful without breaking the bank?

        • Re:Going up... (Score:4, Interesting)

          by ZorinLynx (31751) on Wednesday September 19, 2012 @10:59AM (#41387143) Homepage

          They're cheap because they're mass market items. A lot more people buy TV dongles to watch TV than they do to mess around with SDRs.

          The hobbyist market for SDRs is tiny, and thus it would be very cost-ineffective to manufacture them for just this market. Instead we're taking something that already exists (TV tuners), is mass market, and by coincidence, just happens to be a software-defined radio, and re-purposing it.

          A good analogy would be modifying an existing bicycle to be an electric bicycle, as opposed to manufacturing a dedicated electric bicycle from scratch. Sure, the latter will probably perform better and look nicer but it would be orders of magnitude more expensive, because the market for electric bicycles is small.

          (99% of the electric bikes on the market are just modified mountain bikes)

          • by Obfuscant (592200)

            They're cheap because they're mass market items. A lot more people buy TV dongles to watch TV than they do to mess around with SDRs.

            Using commercial TV hardware to do radio isn't new. Many years ago, the Yaesu FRG9600 used a commercial TV tuner to build a wideband multi-mode receiver. It was kind of a shock to pay good money for the radio, and then open it up to see that almost the whole thing was just one of the ubiquitous PLL/VCO based TV tuners.

            As for the specs not being really great, you don't always need a $1000 radio. Sometimes all you need is a $20 one.

      • Re:Going up... (Score:4, Informative)

        by tlhIngan (30335) <<ten.frow> <ta> <todhsals>> on Wednesday September 19, 2012 @01:27PM (#41389577)

        These super-cheap little dongles are *terrible* performers. They suffer from de-sense when nearby strong stations transmit, tend to have I/Q balance problems, and so on.

        You want good performance from an SDR, you're not going to get it for $20. Providing the dynamic range you need to prevent desense and intermod isn't that easy, nor is providing the sample rate you need to deal with a broad swatch of the receive spectrum at one time at the same time you keep that dynamic range.

        The cost will be several times that (at least.) And there are units on the market (See RFSPACE) that are hundreds of dollars and even over a thousand, but oh, man, once you use one, you'll know why. I have an SDR-IQ (and write free support software for SDRs, including that one) and I live and breathe these things on a day to day basis.

        Yeah, but if you're wanting to experiment with SDRs, do you suggest a hobbyist go out and spend $500+ on a USRP or other high-quality SDR? Or $20, and then make the investment?

        You get what you pay for, but damn for $20, I won't complain about lousy performance when getting started.

        Most SDRs are basically overglorified soundcards - they consist of a tuner frontend coupled with common audio ADCs (thanks to commercially available 192kHz/24 bit and 96kHz/24bit ADCs meant for studio and mastering work).

        Of course, this $20 dongle is 1MHz, but 8 bits (for $20, that's pretty good - high sampling rate ADCs get expensive the faster and more bits you want - top end 100MS/s 24bit can easily run $100+ in 1,000 quantity).

        It's just like people complaining the Raspberry Pi is useless because it's a wimpy processor (though coupled with a fairly good GPU), when (Pandaboard/BeagleBoard/ODROID/etc) gets you far better. Yes, it's true, but the Pi's only $35, versus $150 for the rest.

        There are SDR-based transceivers on the market for a couple of grand that are considered excellent (see FlexRadio) - for under $2000 you can get one, and their latest gen which doesn't expose I/Q data (we're talking about effectively sampling the antenna port! No downconversion so no messing with I/Q signals) can be had for around $6K-ish.

      • by mpilsbury (513793)
        The FUNcube Dongle http://www.funcubedongle.com/ [funcubedongle.com] is good value for money. It has reasonable performance, and starts at 105GBP.
  • Is that FCC ban against full band scanners still in effect? Hopefully software defined radio will render the FCC obsolete, and make such restrictions impossible to enforce.

    • by Anonymous Coward

      The chips have a notch in them "for technical reasons". Three guesses where that notch is.

      • by Anonymous Coward

        Im no radio expert but with most of the chips

        The sites all say the gap is between 1100 - 1250 MHz
        Cell and police, etc are 700-950 (ish)......thought 3g/lte/edge are in the 1Ghz-2.5Ghz
        which *should* be picked up by the chip (how i read it)

        The only thing I can tell is in the "notch" (thanks to a hackaday comment) is
        http://en.wikipedia.org/wiki/Joint_Tactical_Information_Distribution_System

      • If the tuner is designed to work with a cable system there will be no "notch". Cable systems go from 47 MHz to 1000 MHz.
    • by Lumpy (12016)

      They can ban it for the muggles, but all my ham gear will receive anything and does not have any channels blocked out.

  • More info (Score:4, Informative)

    by Anonymous Coward on Wednesday September 19, 2012 @09:57AM (#41386377)

    Reddit also has a section devoted to these dongles: http://www.reddit.com/r/rtlsdr

    A list of USB tuners capable of doing this and where to get them:
    http://www.reddit.com/r/RTLSDR/comments/s6ddo/rtlsdr_compatibility_list_v2_work_in_progress/

  • Wow, dog. (Score:4, Insightful)

    by Anonymous Coward on Wednesday September 19, 2012 @09:58AM (#41386397)

    So, they made a radio out of a radio. And it only cost as much as a radio! How impressive!

    • by L4t3r4lu5 (1216702) on Wednesday September 19, 2012 @10:27AM (#41386745)
      It's radios all the way down.
    • by unixisc (2429386)
      Yeah, initially, I thought they had made a GPLed s/w for reading radio signals on a baseband... But then, I remembered that it's GNU, and there is less to it than meets the eye.
      • I knew something was fishy right in the title. It started with $20 and had GNU in it.

        Yeah, I know, I know. Don't recite the GPL at me. I'm an apostate. Rage on if necessary.

        • by unixisc (2429386)
          Generally, when I see 'radio', I think in this day & age about the RF receiver part of a Bluetooth, Wi-Fi or GPS device, and that this software was about reading the output of that RF circuit to a baseband, and telling the baseband how to operate it. Something that will enable eliminating those evil binary blobs that deny the FSF gang their 'freedom'. The last thing I think about is taking my TV dongle & turning it into a radio. About as useful as turning a motorcycle into a bicycle.
    • A feature was discovered that allows you to do your own decoding. Otherwise this dongle is only good for TV reception in Europe. Now you can receive any kind of analog or digital data as long as it fits in the bandwidth window. Use an upconverter and you can scan the shortwave bands in 2MHz chunks. This $20 dongle does what WinRadio charges $500 for.

  • I should point out that HDSDR [hdsdr.de] is another software radio project.

  • "Granted, the included antenna isn't much and the performance of the receiver is not spectacular, but for $20 or $30, how can you complain?"

    You can't complain, but you can find it irrelevant. There's almost no useful content on FM radio anyway.

    Turning a $20 dongle into a HAM transceiver, THAT would be useful...

    • by Anonymous Coward

      Soft rock isn't much more then $20, plus the sound card. Its a full on transceiver. Better the sound card the better the performance, you don't re a high end card though many use built in sound cards

    • Re: (Score:3, Informative)

      by Anonymous Coward

      Note that the range is 40 - 2200 MHz with dongles that use the Elonics E4000 tuner, and 42 - 1766 MHz with dongles that use the R820T tuner. So you can receive a lot more than FM radio...

    • The point is you can tune from 60-1700MHz (with an L band gap) continuously. Show me a similar receiver for the same price.

    • by Anonymous Coward

      Well, that would be nice, but you can't turn it into a transceiver, because TV receivers have no transmission capability. (Also because any $20 wide-range transmitter would splatter like hell.)

      But it is usable as a ham receiver -- did you really think people are excited about a $20 40MHz-2GHz SDR for listening to FM broadcasts? That's just used in TFA as a toy application that muggles can relate to, to demonstrate the setup. Add a (relatively) cheap single-band transmitter for each band you want to work, a

  • For those who want to stick their toe in the water, this is a great way to get started.

  • by LVSlushdat (854194) on Wednesday September 19, 2012 @12:28PM (#41388559)

    Geez.. Slashdot is *just* now finding out about these? There's been an info page over on Reddit regarding these for literally months. Darned thing work fine for ham radio 2m and 440 repeater monitoring, plus covers like 64-1700mhz.. http://www.reddit.com/r/RTLSDR [reddit.com].. Sure, they have their problems, but for $20-$25, WHO THE HELL CARES??

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