∏ NODE

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 also the soon to be released HackRF (~$300USD) and BladeRF SDRs ($420 and $650), which can both transmit and receive.

Softwares

[gqrx](http://gqrx.dk/) : easy to use software
[pd-rtlsdr](https://github.com/tkzic/pd-rtlsdr) to drive an rtl-sdr device from Pure Data
[ACARS decoder](https://sourceforge.net/projects/acarsdec/) for airplanes
[dump1090](https://github.com/antirez/dump1090) also for airplanes

Ressources

[Lessons](https://greatscottgadgets.com/sdr/) from the inventor of HackRF one
[Official rtl-sdr osmocom website](https://osmocom.org/projects/rtl-sdr/wiki/Rtl-sdr)
[Google groups forum](https://groups.google.com/forum/#!forum/ultra-cheap-sdr)
[RTL-SDR community Wiki](http://www.rtlsdr.org/start)
[dxzone.com](https://www.dxzone.com/) - A good ham related database useful for research

dangerousprototypes.com - A blog about open source hardware projects that often has SDR related posts.
hackaday.com – A blog about DIY hardware that also often has SDR related posts.
radioforeveryone.com - SDR for mariners. A new blog about marine related RTL-SDR applications.
EEWeb.com - A large electrical engineering news and community website that sometimes feature SDR related stories.

Interesting Applications

With an upconverter:

Decoding digital amateur radio ham communications such as CW/PSK/RTTY/[SSTV](https://www.rtl-sdr.com/receiving-sstv-with-rtl-sdr/).
Receiving[ digital radio monodial shortwave radio ](https://www.rtl-sdr.com/tutorial-drm-radio-using-rtl-sdr/)(DRM).

Specifications

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
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.

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 3.2 MS/s working well on USB 3.0.

Resolution

The resolution is 8 bits.

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.

Comparisons with other Software Defined Radios

Screenshots

M 147-9 graz.png Graz 147.9 amradio