What is RTL-SDR?

RTL-SDR is a very cheap software defined radio that uses a DVB-T TV tuner dongle based on the RTL2832U chipset. With the combined efforts of Antti Palosaari, Eric Fry and Osmocom it was found that the signal I/Q data could be accessed directly, which allowed the DVB-T TV tuner to be converted into a wideband software defined radio via a new software driver.

Essentially, this means that a cheap $20 TV tuner USB dongle with the RTL2832U chip can be used as a computer based radio scanner. This sort of scanner capability would have cost hundreds or even thousands just a few years ago. The RTL-SDR is also often referred to as RTL2832U, DVB-T SDR, or the “$20 Software Defined Radio”.

There are many other software defined radios similar to the RTL-SDR, but they all come at a much higher price. The FunCube PRO+ is a good receiver similar to the RTL-SDR, priced at around $190 USD. There is now also the Airspy ($200) and SDRPlay ($300). Then there are the HackRF ($300USD) and BladeRF SDRs ($420 and $650), which can both transmit and receive.

What is Software Defined Radio?

Radio components such as modulators, demodulators and amplifiers are traditionally implemented in hardware components. The advent of modern computing allows these traditionally hardware based components to be implemented into software instead. Hence, the software defined radio. This enables easy signal processing and thus cheap wide band scanner radios to be produced.

What are some RTL-SDR Radio Scanner Applications?

The RTL-SDR can be used as a wide band radio scanner. Applications include

Furthermore, with an upconverter or direct sampling mod to receive HF signals the applications are expanded to

  • Listening to amateur radio hams on SSB with LSB/USB modulation.
  • Decoding digital amateur radio ham communications such as CW/PSK/RTTY/SSTV.
  • Receiving HF weatherfax.
  • Receiving digital radio monodial shortwave radio (DRM).
  • Listening to international shortwave radio.
  • Looking for RADAR signals like over the horizon (OTH) radar, and HAARP signals.

Note that not all the applications listed may be legal in your country. Please be responsible.

What is the RTL-SDR frequency range?

This is dependant on the particular tuner variant used in the dongle.

Tuner Frequency range
Elonics E4000 52 – 2200 MHz with a gap from 1100 MHz to 1250 MHz (varies)
Rafael Micro R820T 24 – 1766 MHz (Can be improved to ~13 – 1864 MHz with experimental drivers)
Fitipower FC0013 22 – 1100 MHz
Fitipower FC0012 22 – 948.6 MHz
FCI FC2580 146 – 308 MHz and 438 – 924 MHz (gap in between)

Table Source: Osmocom

As you can see from the table, the Elonics E4000 and Rafael Micro R820T dongles have the greatest frequency range.

What is the RTL-SDRs sample rate?

The maximum sample rate is 3.2 MS/s (mega samples per second). However, the rtl-sdr is unstable at this rate and may drop samples. The maximum sample rate that does not drop samples is 2.4 MS/s, however some people have had luck with 2.8MS/s and 3.2 MS/s working well on some USB 3.0 ports.

What is the RTL-SDR’s ADC resolution?

The native resolution is 8 bits, but the Effective Number of Bits (ENOB) is estimated at ~7. Decimation in software may raise this value.

What is the RTL-SDR input impedance?

Since these dongles are intended for TV, all dongles will have an input impedance of 75 Ohms. However, the mismatch loss when using 50 Ohm cabling will be very minimal at the frequencies the dongle can cover.

The 75 Ohm impedance for the R820T can be checked on the datasheet which can be downloaded here.

What are the minimum PC requirements?

Generally, at least a dual core processor of some sort will be required for most general GUI based software defined radio software. Command line tools and ADS-B decoders may work with less powerful hardware.

What dongle should I buy?

The cheapest, most common an generally best performing dongle at the moment is the Rafael Micro R820T. It can be bought for about $20 USD.

The Elonics E4000 used to be the most common, but Elonics has closed and ceased chip production, making the E4000 rarer and much more expensive these days.

The R820T also is generally regarded as having better performance and sensitivity for most interesting frequencies. For ADS-B, the R820T is much more sensitive at 1090 MHz. There are now also the R820T2 dongles, which offer increased sensitivity over the R820T. For these reasons, the R820T2 is currently the recommended dongle, unless you need the greater frequencies that the E4000 provides and are willing to pay a premium.

Be careful when buying a dongle as certain sellers tend to misrepresent their devices (knowingly or unknowingly) as having compatible tuners, when in fact they may send out a device with an incompatible tuner. Also be wary when buying E4000 dongles from auction sites as there are many dodgy sellers incorrectly advertising R820T/2 dongles as the rare E4000.

See our RTL-SDR purchasing guide page for more information about where to obtain dongles from reputable sources.

I already have a USB TV Tuner, is it Compatible?

If your TV tuner contains an RTL2832U chip it is probably compatible. If it does not contain this chip, it is not compatible. A list (somewhat out of date) on compatible and incompatible tuners can be found on this reddit wiki page.

Comparisons with other Wideband Commercial Software Defined Radios

SDR Tune Low (MHz) Tune Max (MHz) RX Sample Rate (MHz) ADC Resolution (Bits) Transmit?(Yes/No) Price ($USD)
RTL-SDR (R820T) 24  1766 3.2 8 No ~20
Funcube Pro+ 0.15
0.192 16 No ~200
Airspy 24 1800 10 12 No 200
SDRPlay 0.1
8 12 No 300
HackRF 30 6000 20 8 Yes 300
BladeRF 300 3800 40 12 Yes 400 & 650
USRP 1 DC 6000 64 12 Yes 700
MatchStiq 300 3800 28 12 Yes 4500

Useful Links

http://sdr.osmocom.org/trac/wiki/rtl-sdr – Official rtl-sdr osmocom website

http://www.reddit.com/r/RTLSDR – Reddit rtl-sdr forum

https://groups.google.com/forum/#!forum/ultra-cheap-sdr – Google groups forum

www.sdrsharp.com – SDRSharp official website

www.rtlsdr.org – RTL-SDR community Wiki

http://www.dxzone.com/ – A good ham related database useful for research

http://www.dangerousprototypes.com – A blog about open source hardware projects that often has SDR related posts.

http://www.hackaday.com – A blog about DIY hardware that also often has SDR related posts.

http://sdrformariners.blogspot.com/ – SDR for mariners. A new blog about marine related RTL-SDR applications.

http://www.EEWeb.com – A large electrical engineering news and community website that sometimes feature SDR related stories.

http://labyrinth13.com/ – Strange Beacons. Radio user who records and makes videos about several interesting signals he finds. Often uses an RTL-SDR.

For a comprehensive book about the RTL-SDR you may be interested in our eBook available on Amazon.

The Hobbyist’s Guide to the RTL-SDR: Really Cheap Software Defined radio.


  1. ben

    What sdr hardware (R820T RT2832U dongles) is the best platform at the moment? SDR#? Portable SDR (PSDR)?

    Is it possible to use such a dongle to record/analyze any RF signal, from like a remote control light switch? Can it also play AM/FM radio?

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  3. Curt Rowlett - Strange Beacons

    Thank you very much for the link to my website. I owe much to your blog and website. It was because of the great “Quick Start” guide you provide that I was able to easily setup and configure SDR for my computer. Thank you very much for that and for continuing to post interesting stories about the many uses of this technology. Regards.

  4. M M Iqbal

    Could you plz let us know whether you may provide a solution for;

    1. Detecting and auto recording of real time particular speech or voice passed over mobile phone conversation;
    2. Detecting the mobile phone number(s) which were active at a specific place of abduction/Kidnapping.
    These to be used by govt law enforcement authority.
    Hope to Hearing from your end.

    Thanking you,

    With Best Regards,

    Dr. Muhd M. Iqbal
    Pentagonal Advanced Technologies
    House # 04, Block # A, Mamudpur
    Bhuigar, Narayanganj, BANGLADESH
    Tel: 01748 041104 / 01977 770101
    E-Mail: pentagonalbd@yahoo.com

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