Rtl sdr

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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

Ressources

Interesting Applications

With an upconverter:

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.</p>

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

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 64 1700 0.096 16 No 150
Funcube Pro+ 0.15
410
260
2050
0.192 16 No 200
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



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Screenshots

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