A $20 Software Defined Radio For GNU Radio

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A $20 Software Defined Radio For GNU Radio

Posted by Unknown on Wednesday September 19, 2012 @01:45AM from the fcc-commissioner-brunt-makes-surprise-appearance dept.

An anonymous reader writes "Dr. Dobb's shows how to take a $20 USB TV dongle and use it as a wide-range software defined radio using GNU Radio." See also the OscomSDR project, and SDR#, an MIT licensed program for debugging software defined radios.

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Going up... by pushing-robot · 2012-09-19 01:49 · Score: 4, Insightful

Wow, inflation is really hitting these things...
http://hardware.slashdot.org/story/12/03/31/1914217/software-defined-radio-for-11

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1. Re:Going up... by Anonymous Coward · 2012-09-19 02:04 · Score: 4, Informative
  
  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.
2. Re:Going up... by BLKMGK · 2012-09-19 02:17 · Score: 3, Insightful
  
  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?
  
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3. Re:Going up... by ZorinLynx · 2012-09-19 02:59 · Score: 3, Interesting
  
  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)
4. Re:Going up... by tlhIngan · 2012-09-19 05:27 · Score: 3, Informative
  
  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.
More info by Anonymous Coward · 2012-09-19 01:57 · Score: 4, Informative

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. by Anonymous Coward · 2012-09-19 01:58 · Score: 4, Insightful

So, they made a radio out of a radio. And it only cost as much as a radio! How impressive!
1. Re:Wow, dog. by L4t3r4lu5 · 2012-09-19 02:27 · Score: 3, Funny
  
  It's radios all the way down.
  
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Re:No description? by gl4ss · 2012-09-19 02:08 · Score: 3, Informative

At least the author was kind enough to provide links that explain things.
well, it's a dupe so why bother with explanations?
anyhow, http://www.gnss-sdr.org/documentation/gnss-sdr-operation-realtek-rtl2832u-usb-dongle-dvb-t-receiver if you're wondering what kind of things can be done with it, one of the uses is receiving gps signals..

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Re:Whats the point? by Anonymous Coward · 2012-09-19 03:29 · Score: 3, Informative

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...
Slashdot is WAAAAY behind.. by LVSlushdat · 2012-09-19 04:28 · Score: 4, Informative

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.. Sure, they have their problems, but for $20-$25, WHO THE HELL CARES??

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