Software defined radio from a USB TV capture card

With a simple digital TV USB capture card, you can build your own software defined radio or spectrum analyzer. While it may not be as cool as [Jeri Ellsworth]‘s SDR, it’s still very useful and only requires $20 in hardware.

The only piece of hardware required for this build is a USB FM/DTV capture device with the Realtek RTL2832U chipset. So far, two USB sticks have been tested and the unit with the largest frequency range (64 – 1700 MHz) is available direct from China for $20.

Turning these cheap capture cards into software defined radios and spectrum analyzers was discovered by [Antti Palosaari] after sniffing the device. These cards demodulate the frequency and send all the data to the computer and is decoded via software. If you have one of these capture cards lying around, you can grab the software and load it up on your *nix box. Right now, the software only writes directly to a file, and may drop a few samples if writing to a hard disk instead of ram. Small problems, but we’re sure this project will pick up steam in the very near future.

via reddit

Comments

  1. Neckbeard says:

    So… Its the same concept as the Funcube Dongle and seems to use the exact same chip?

    • Playaspec says:

      @Neckbeard It looks like the same front end, but the FunCube appears to use USB sound card hardware to do the sampling. FunCube website says ~96KHz I/Q, whereas according to the SDR thread, the sample rate in the example was 2.048 MHz. It would have to have a faster ADC to handle video data rates. This also explains why the FunCube is driverless, and this thing is going to require more hacking to make a useful driver.

  2. Matt says:

    Wow, this beats the pants off the price of the Funcube Dongle though!

    /me excited

  3. Philip says:

    You have a broken link there(direct from China).

  4. Knightmare says:
  5. Sylvain Munaut says:

    A couple of comments:

    1) The stick doesn’t have a preamplifier like the FDCP have => Sensitivity is clearly not as good

    2) The stick only sends 8 bits IQ sample, so the dynamic range is pretty limited.

    3) Beware that not all stick using the RTL2832 have a elonic E4000 tuner. Some have another models and those can be much more limited

    4) While the availability of the raw mode was indeed discovered by Antti Palosaari while looking at a FM mode capture, it’s important to note that all the work for finding exactly how to exploit it and write the actual software was done by Steve Markgraf.

  6. doc oct says:

    So does this decode the DVB-T streams in software, or just the FM radio stuff? I’d suspect it’s just FM radio stuff, but curious to know. I ordered one right away when I got the email for this post.

  7. Alex Rossie says:

    can this be sued with gnu radio? if so WANT!

  8. Alex Rossie says:

    for god sake, why does do I always need to click every link in the description for find the article

  9. joph says:

    Nice, I’ll try it this weekend with my DigiVox mini II V3.0 stick.

  10. Hirudinea says:

    Gotta love it when you find out something cheap can be made useful with a little hacking.

  11. grindel says:

    I want this, but dealextreme is 3 weeks behind on my last order (ordered 2/26/12). Has anyone found a local source?

  12. Skeltorr says:

    But CRDA restricts you to 5 nano watts of power and channels 5+6! the FCC is my lord and master

    • draeath says:

      That’s funny, they have these licences that you can get that give you all sorts of privileges!

      Also: WTF Hackaday!!! “That email address is associated with an existing WordPress.com (or Gravatar.com) account. Please click the back button in your browser and then log in to use it.”

  13. james says:

    Guys, bad news – they are out of stock at dealextreme, but you can still get them at aliexpress

    • Hamish says:

      It didn’t say they were out of stock when I checked

      • moofree says:

        Dealextreme never shows updated stock information.

        I canceled my order at dealextreme last night and placed one on aliexpress and it’s now sold out there.
        Annoyingly, the seller didn’t process my order when it was still in stock as he saw I was in the USA which uses ATSC.

        ETA “15-20 days” for aliexpress; “Who knows?!” for Dealextreme.

  14. Roklobsta says:

    For those in Australia Catchoftheday and Zazz have the ezCap dongle for sale every few months.

  15. markS says:

    you can buy directly from easycap

    http://www.usbeasycap.info/

    and yeah WTF on login ..?

  16. markS says:
  17. Roklobsta says:

    I have a dongle and the receiver is quite weak. Even with a DVB transmitter only 5km away I don’t get a TV signal but I do get FM on it using the supplied little antenna.

    A good and cheap 70MHz to 2GHz amplifier to go with the dongle might be this:

    http://www.minikits.com.au/kits2.html#pha1

  18. Chewie says:

    Now THIS is the stuff that should be on this site. Cool!

  19. grindel says:

    What do you think the odds are that the ATSC version (the one that would work with US TV) would have the same capabilities?

    http://usbeasycap.com/index.php?main_page=product_free_shipping_info&cPath=5&products_id=65&zenid=1d4oaldtrfo2mj5u0sog1oa653

    • Roklobsta says:

      Unless you want to use the dongle to watch TV in the USA there is no need to buy an ATSC version – just get the DVB/DAB/FM one. The model I have is EZTV646 but the PCB is exactly the same as the one in the picture – including the EZTV668 1.1 text.

      • Matthew B says:

        The issue that I have run into is that the DVB version uses the “Television Aerial” coaxial plug, so its not compatible with any store bought or homebrew antennas in the US that use the F-connector. Radio shack has an adapter for $10, but I am concerned about an unneccessary cost and loss of dBs. Any thoughts on this? Does the ATSC version of this dongle have pretty much the same guts as the DVB/DAB/FM one? Can the ATSC one be purchased to use with HD-SDR?

  20. Edgar says:

    This is nowhere near as useful as the funcube due to the built in ADC converter. It is only 7-bit. You may be able to receive broadcast FM (which is the initial purpose of the device), but not good for much else the resolution is not there.

    • james says:

      8, as in 8 bit. not 7.
      And as it was already stated 8 bit is enough for fm, dab, dab+, tetra, gsm, gmr.
      But hey, i’d certainly take more than 8 bit for 20$ any time…. feel free to suggest something.

    • AE5PH says:

      Besides what James said, the consequence of having 8 bits versus 16 or 24 bits is that there is not as much dynamic range available (48 dB vs 96 dB and 144.5 dB, respectively). An adjustable preamplifier or attenuator can bring the received signal into the range handled by 8 bits. You can also utilize oversampling and decimation to increase the resolution, hence the dynamic range. For example, to increase the resolution from 8 to 11 bits, oversample the data at a rate 64 times that desired. If the sampling rate is 2,560,000 samples per second, the effective sample rate will be 40,000 samples per second, which is still a useful I&Q sample rate for SDR. There is plenty of information on oversampling and decimation available through Google, so I won’t go into the details here.

  21. Conundrum says:

    I have a broken DVB-T stick here.
    Might try and fix it, IIRC it was
    broken remote at the time.
    The stick shows up but won’t install
    and I can’t locate a driver.

  22. Paul says:

    Conundrum, you need a DAB stick, I have a DVB-T stick but the requirenent is for the wide band DAB output.
    This seems to be moving very fast I’m ordering my DAB stick, an 8 bit 2MHz wide SDR for $20, yes please.

  23. Paul says:

    Found that the receiver chip can be used for GPS and I’m sure it’s wide enough for ADS-B, and of course polar orbit weather sats. These could be the handiest radio bits ever.

  24. Beth says:

    What about aviation (air) band, ~108 to 137MHz AM (not FM)?

  25. derek says:

    I can confirmn the sticks indeed work well, get anymake, as long as it has the required chip sets.. It compliments the funcube very well

    I use my stick for airband, SATs and FM broadcast reception. The available dll will work with Winrad, WR+, HDSDR etc Also works with GNU radio

  26. Tulani says:

    Mine there is no sound came

  27. Has anyone tried adding one of these to openwrt? How awsome would it be to stream the feed from a remote wifi router you can place anywhere? We could create a meshed digital repeater input, with multiple listening stations on the same frequency. A repeater node if you will, with listening redundancy. Simular to a cellular network.

  28. Sid Boyce says:

    Support for these dongles is included in ghpsdr3-alex which I and others have used them as SDR’s on the amateur radio bands 2m and 70cms, all modes supported.

    http://napan.ca/ghpsdr3/index.php/Main_Page

    The rtlsdr-server talks to the dongle and dspserver puts it on the local network and on the internet, accessible using QtRadio on a PC/netbook running Linux or Windows and glSDR from Google Play on an Android phone or tablet.

    I have the bits to build an HF upconvertor so they can be used to receive the MF/HF bands also.
    http://blog.kf7lze.net/tag/up-converter/ and other references via google.

  29. This Rookie thanks all above for the sound advice! xx

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