RTL-SDR

RTL-SDR is a very cheap ~$25 USB dongle that can be used as a computer based radio scanner for receiving live radio signals in your area (no internet required). Depending on the particular model it could receive frequencies from 500 kHz up to 1.75 GHz. Most software for the RTL-SDR is also community developed, and provided free of charge.

What is Software Defined Radio?

Radio components such as modulators, demodulators and tuners are traditionally implemented in analogue hardware components. The advent of modern computing and analogue to digital converters allows most of these traditionally hardware based components to be implemented in software instead. Hence, the term 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:

   Use as a police radio scanner.
   Listening to EMS/Ambulance/Fire communications.
   Listening to aircraft traffic control conversations.
   Tracking aircraft positions like a radar with ADSB decoding.
   Decoding aircraft ACARS short messages.
   Scanning trunking radio conversations.
   Decoding unencrypted digital voice transmissions such as P25/DMR/D-STAR.
   Tracking maritime boat positions like a radar with AIS decoding.
   Decoding POCSAG/FLEX pager traffic.
   Scanning for cordless phones and baby monitors.
   Tracking and receiving meteorological agency launched weather balloon data.
   Tracking your own self launched high altitude balloon for payload recovery.
   Receiving wireless temperature sensors and wireless power meter sensors.
   Listening to VHF amateur radio.
   Decoding ham radio APRS packets.
   Watching analogue broadcast TV.
   Sniffing GSM signals.
   Using rtl-sdr on your Android device as a portable radio scanner.
   Receiving GPS signals and decoding them.
   Using rtl-sdr as a spectrum analyzer.
   Receiving NOAA weather satellite images.
   Listening to satellites and the ISS.
   Radio astronomy.
   Monitoring meteor scatter.
   Listening to FM radio, and decoding RDS information.
   Listening to DAB broadcast radio.
   Listening to and decoding HD-Radio (NRSC5).
   Use rtl-sdr as a panadapter for your traditional hardware radio.
   Decoding taxi mobile data terminal signals.
   Use rtl-sdr as a high quality entropy source for random number generation.
   Use rtl-sdr as a noise figure indicator.
   Reverse engineering unknown protocols.
   Triangulating the source of a signal.
   Searching for RF noise sources.
   Characterizing RF filters and measuring antenna SWR.
   Decoding Inmarsat STD-C EGC geosynchronous satellites.
   Listening to the ISS (International Space Station).

Furthermore, with an upconverter or V3 RTL-SDR dongle 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 mondiale 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 dependent on the particular tuner variant used in the dongle, and the particular implementation. Some dongles, like our RTL-SDR Blog V3 also utilize the direct sampling mode which can enable reception below 28 MHz. Tuner Frequency range Elonics E4000 52 – 2200 MHz with a gap from 1100 MHz to 1250 MHz (varies) Rafael Micro R820T/2 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/2 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 2.56 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.

Dropped samples are okay if you are just visualizing the spectrum, but will cause problems if you want to demodulate/decode signals.

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

www.rtlsdr.org - RTL-SDR community Wiki (not updated in a while)

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://radioforeveryone.com/ - Formerly known as "SDR4Mariners". Another blog about RTL-SDR and radio projects.

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

https://www.elecrow.com/ - Full Raspberry Pi Kit. Probably useful for an RTL-SDR carry kit.

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.