A quick introduction to Software Defined Radios
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README.md

SDR 101

*This repo was originally created for an ArtSec meetup on Software Defined Radios

##Getting Started

What are Software Defined Radios?

Currently most radios you can buy off-the-shelf are designed to do one thing. Like Bluetooth, or Wi-Fi or GSM. However Software Defined Radios allow you to use the same hardware to "program different radio architectures". The analogy I like to use is that current radi chipsets are like calculators and software defined radios are computers.

"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 makes them special?

In case you're wondering what makes this possible, its the falling price of hardware.

With the advent of USB 3.0 it is possible to get really high sampling rates that are usually needed to decode signals at high frequencies.

Powerful microcontrollers that run the board and program the FPGAs are pretty cheap.

Chips known as FPGAs and CPLDs are basically integrated circuit breadboards that you can program to be whatever you want. These are the boards hardware manufactures use when they are desinging new integrated circuits and have traditionally been frightfully expensive.

What are the different boards out there?

Specs RTL SDR Hack RF Blade RF USRP (B100)
Price 20$ 320$ 420$ ~ 600$
Open Source Everything HDL + Code Schematics Host code
Radio Spectrum ~ 50Mhz - 1.5 Ghz 30 MHz – 6 Ghz 300 MHz – 3.8 GHz 50 MHz –2.2 GHz
Bandwidth 2.8 Mhz(max stable) 20 MHZ 28 MHZ 16 MHz
Duplex Half (Rx only) Half Full Full
Sample Size 8 - bit 8-bit 12-bit 12/14 12-bit
Sample Rate 2.4 MS/s 20Ms/s 40 Msps 64/128 Msps
Interface USB 2.0 USB 2.0 USB 3.0 USB 2.0
Good For FM, NOAA Satellites GSM, A/NTSC GSM,ATSC,NTSC, GSM

The RTL-SDR is by far the cheapest board out there

Art Hack Day TV

For Art Hack Day Jonathan Dahan and I set up a small television broadcast station. We used the Hack RF and modified code we found online to broadcast a slide show of images from the Hack RF to UHF Channel 9

Code from that project is available here

GSM With SDRs

Disclaimer: GSM is a licensed band and if you transmit and are caught transmitting the FCC will give you trouble.

Having said that there are a lot of projects out there that allow you to use SDRs to create a standalone GSM network.

The oldest and most well known is openBTS.

Others include YateBTS and OsmoBTS

For more information on the GSM aspect of SDRs I suggest looking through the materials for Towers Of Power a course taught at ITP by the amazing Benedetta Piantella that aims to teach students about GSM networks. How they work, their politics and how to use them in projects. The link above has a lot of good material for anyone more interested in GSM.

I also wrote a couple of tutorials on setting up gsm networks using Yates and Osmo with the Blade Rf and USRP1 respectively. Linked below

Setting up Blade RF with Yates BTS

Setting up USRP1 with Osmobts

I have live images for these if anyone is wants them let me know.

Resources

SDR Tutorials by Michael Ossmann

SDR Book for theoretical fundamentals

References

OpenMHz Receiving HRPT Weather Satellite

High Altitude Balloons HAB

Jiao Xianjuns amazing Git Hub repo

Watch TV using the RTL2832U dongle