Guide to RTL SDR

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What is SDR ??

SDR short for Software Defined Radio is a system in which general electronics hardware of a communication system is replaced by it’s software counterparts. This can be achieved in different ways. For example, a typical SDR receiver will consist of a Hardware RF front-end, a local Oscillator and a Mixer, using direct conversion the Mixed output is fed to an analog to digital converter or a PC sound card for sampling or a Using a superheterodyne principle to an IF is sampled using a ADC or PC soundcard and a software.

A very simple and practical example of a SDR is a DRM (digital Radio Mondiale). A normal general coverage superheterodyne receiver with 455 KHz IF is used along with a frequency down converter. As the range of a PC soundcard is limited to around 24 kHz. The 455 KHz IF is mixed with a Local Oscillator frequency of around 467 kHz to derive a down converted output signal of 12 KHz, this is then fed to a PC soundcard Line IN port. The receiver is tuned to a DRM station, with the downconverted 12 Khz output fed to a computer and a DRM receiver software called Dream decodes the digital audio signal.

SDR is used in numerous applications. It also finds a lot of interest a month Amateur radio community. Various SDR receivers and transceivers both homebrew and commercial ones like SoftRock, Flex Radio, Perseus, etc. have been in use and new designs are being created regularly.

What is RTL SDR ??

RTL SDR IndiaIn Europe, DVB-T is a standard for Digital Terrestrial TV transmissions.  The market is flooded with DVB-T TV tuner Dongles based on RTL2832U Chipset (RTL stands for Realtek).  A lot of these dongles are chinese and are as cheap as $8 (Rs. 500).  Some time in the year 2010 a developer Eric Fry accidentally discovered SDR capabilities of these dongles while trying to get them working on Linux for FM and DVB reception.  An email by Antti Palosaari in 2012 about this discovery on the linux driver development mailing list kicked the action on further development of drivers for Realtek RTL2382U along with some work on these dongles by Osmocom based on their own E4000 based SDRs.  Though there was some confusion about who discovered the SDR capabilities of these dongles, it is now confirmed that Eric was responsible for this discovery and the later developments to getting the RTL2832U to work was done mostly by Antti and Osmocom.

Now coming to the the important points, the dongles.  There are multiple DVB-T dongles available in the market based on the RTL2832U chipset.  They differ based on the tuner chip they use.  Most common tuners are E4000 and R820T.  Most of the initial work was done on the E4000 tuners (Elonics E4000).  Though these Dongles were made only for DVB-T reception, their frequency range was quite high from 54-2200 MHz (with gap of 1100-1250 MHz). Currently, the most widely used tuner is R820t (from Rafael Micro) support for these was added to the development much later, but is now fully operational.  R820t has a better frequency range from 24-1700 MHz and with some simple mods (both software or hardware) this range can be brought down to work from 0 to 1700 Mhz.  One can also use frequency upconverters to tune the frequencies below 24 MHz.

The name RTL SDR is thus based on the Chipset manufacturer RTL for Realtek and SDR for Software defined Radio.

Where to find more information about RTL SDR ??

RTL SDR has a huge community both users and developers. I am listing some of the resources to follow to keep up with this technology:

Official wiki for RTL SDR

Join IRC channel ##rtlsdr at freenode.net.  This is a very active IRC channel for any help you need around RTL SDR.
Reddit has quite a big repository of information related to RTL SDR with a huge active user base.
A Google group is also setup to discuss Ultra Cheap SDR options.
Yahoo Group for RTL SDR.
A Google+ community for RTL SDR.
http://www.rtl-sdr.com/ has hundreds of tutorials, guides and videos on working with RTL SDR
http://www.superkuh.com/rtlsdr.html is another such blog for RTL SDR

Where to buy RTL SDR DVB-T dongle in India ??

The most convenient source of buying RTL SDR dongles in India is eBay for now.  Leave alone brick and mortar shops, even Indian online stores do not sell these dongles.  These dongles mostly being chinese have huge number of vendors on eBay from places like China, Hongkong, etc.  Their cost ranges from $5 to $20.  You have to make a payment using credit card and they ship it usually buy post which takes around 25 to 30 days to reach your address (if you are in India).  It should be possible to convince the seller to ship it by courier with a tracking number by paying extra.  I bought it from eBay (its been a while, I cant remember the seller) for $8 and it reached me (Pune, India) on the 27th day.  I kept following up with the postman.

eBay seller with good rationThere are a number of sellers on eBay you can buy this from, it would not be fair on my part to list specific sellers.  Any seller selling it at approximately $8 – $10 should be fine.  I have seen a lot of vendors on eBay with a 98% +ve feedback and hundreds or even thousands of products sold.   So, make sure the seller has good rating and he has sold good number of products and achieved that rating.  The example this picture shows a good eBay seller, this seller has received more than 3 lack feedbacks and has maintained more than 98% +ve feedback.  (Number of feedbacks should usually depend on the number of transactions, thus this user must have done more than 3 lack transaction on eBay and achieved this rating, which means this is one of the best eBay seller).

Update:

RTL-SDR.COM has been selling this dongle with high quality (military standard??) components and in a metal case at around $24 and with free registered international shipping.  That’s the best one can get for the price. find it here.  They even have an Indian re-seller (a little expensive though).

This is some of the basic information you’ll need to jump into the cheapest SDR available in the market today.  If you have some suggestion regarding this post or have some pointer to where one can buy these dongles cheap, leave your comments below.

Amogh Desai
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33 Comments


  1. Sir, can you please give the link to the exact product on ebay ? Further, wouldn’t the item be stuck in the customs as its illegal to intercept certain freq in india ?

    Reply

  2. Sir how much it cost you including shipping cost in INR.

    Reply

  3. Very beautifully written and explained. Please be noted that a company from India Saankhya Labs, based out of Bangalore, India makes Demod chips which can be used to make SDR. And also Apache labs again Gurgaon India makes highly professional and highly acclaimed SDRs.

    It makes me feel proud.

    Best Regrds,

    Sudip Kar

    Reply

  4. Greetings and All The Best wishes.
    Wonderful project, easyly to understandable . I Like them. This is VU2VIZ, Syed Mohiddin,

    Reply

  5. Its wonderful.
    i am planning to buy it.
    as i am a resident of Hyderabad, India, where do i receive DVB-T signal in india to tune it down and use it for processing.

    how can it help me to work on SDRs in INDIA

    Reply

  6. Your post was very helpful, it gave me the confidence that i can do this in India. I purchased a DVB-T, there are India-based sellers too now

    Reply

  7. very well written Amogh desai and should be useful for SDR beginners who would like to buy the dongle and start catching up some airwaves.

    I also wish to buy the card but its selling costly at eBay india for Rs.2500+ compared to cheaper options outside India.

    Want a cheaper and reliable buying option to start with as an radio amateur.

    Reply

      1. Hello sir, I have purchased a Iball Claro Tv tuner with Fm. But I’ve tried everything but sdr sharp still says device not detected. Please tell me if I can make this work or not? I’ve tried replacing the drivers with zadig but it still does not work

        Reply

        1. Hi Akshay,

          Please check what chip (IC) this dongle uses for TV reception. RTL SDR uses a RealTek Demodulator IC RTL2832U and R820T Tuner from Rafel. These are readily supported by SDR# as well as other software like Power SDR, HD SDR, SDRRadio.com, etc. If your iBall dongle has some other IC inside which is not supported by these software, it will not work. I suggest you to possibly return the iBall dongle and buy proper RTL SDR dongle as i have not found anyone using/supporting the iBall dongle.

          -Amogh
          VU3DES

          Reply

    1. What is price ?? Work on pc and android device??

      Reply

  9. I am planning to order one. How likely is my chance of getting caught it in Indian customs ?

    Reply

  10. Hi, Amogh
    I am not received any registration email from electronics forum..recently I registered with different user I’d n email but not received activation email, so kindly fix my problem

    Reply

  11. Sir,

    What is the difference between T and T2 dvb ?

    Delhi

    Reply

  12. Need to know how to get Ham Radio License training in Pune.

    Appreciate some details on whom I can contact.

    Thanks & Regards,
    Pradnya Joshi

    Hi Amogh Desai,
    Can you please share your contact details so that I can contact you to get more details.

    Thanks,
    Pradnya.

    Reply

    1. Hi Pradnya,

      I’ll be glad to help you to get into the exciting world of Amateur Radio. Please check your email for further details.

      VU3DES
      Amogh

      Reply

  13. Does using a sdr and listening to radio require a ham license? Also, are the ham exams held in Pune, and where if they are.

    Thanks

    Reply

    1. Hi Sameer,

      Listening to radio on SDR or any radio for that matter doesn’t require license. License is only required for transmission.

      Please follow/like PHARC FB page for future activities, workshops, exam dates etc.

      73s
      Amogh
      VU3DES

      Reply

  15. Hello Sir,
    Is receiving ATS signal illegal? And are all sdr supported in India. If not then which, I want to buy asap.

    Reply

  17. Dear Amol,
    I am Sudhir Phakatkar VU3CGD
    I am interested in RTL-SDR dongle for radio meteor activates.
    Please may I get your contact to discuss more about purchasing it.
    Regards,
    Sudhir
    9766783467

    Reply

  18. Hi Amogh

    Thanks for detailed post, i am trying to get HackRF One, but the seller is asking for ” End User application” approval letter. Do you have any idea how to get it and whom to approach for it?

    Thanks.

    Reply

  19. Hi Amogh,

    I am lucky to end up in your blog and to find a knowledge mine this big. I am a cybersecurity hobbyist and was looking for experimental setup for GSM sniffing, cell triangulation, and so on. And all these would require an SDR. That is how I started with SDR and the legal requirements to own an SDR transceiver in India. That landed me into Radio licensing, then the NIAR website, and your blog. I have gone through your blog mostly and the projects you pulled off are no short of brilliance. I have a fe questions if you can help me out.

    1. Is it legal to own any SDR transceiver kit? You mentioned receiver is legal, but what about transceiver? Do I need Amateur Radio Operator license for that?

    2. Any genuine online shop to buy equipments for SDR in India? I am looking for HackRF One or LimeSDR kits.

    3. Your blog got me interested in HAM radio. Any genuine online shop to buy HAM radio equipments? Looking for antenna, transceiver, telegraph key, Morse code oscillator.

    Thanks!
    Subhajit

    Reply

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