A software defined radio is basically a oscillator that allows you to work within a certain frequency range. SDR is the best device out there for analyzing anything in the RF spectrum. Default it can’t do much without the application that allows it to do certain tasks. Think of it like this if you wanted to build a wifi device or a bluetooth hardware device you have to have specific chips that allow it to do this that filter and all kinds of things. With SDR you can use blocks in GNU radio to replace those hardware chips. So basically you can do anything wireless with this device. You can access cell phones, read text messages, read bluetooth, turn cars off on the freeway, make rouge cell phone towers, triangulate, demodulation, watch TV, listen to the radio, use as a GPS, read RFID and pretty much anything wireless!
There are a lot of options for SDR devices. Currently I only recommend going with a device that is compatible with SOAPY SDR which is a hardware agnostic interface for SDR hardware. Basically it allows you to interface with one library to connect it to many applications such as GNU Radio or Qspectrumanalyzer.
The top choices are as follows.
- Lime SDR USB – I recommend this device because its full duplex and allot more powerful than other devices. Plus is has a expansion board that allows it to go up to 10ghz. One issue with it tho is its sweep rate is low due to the fact that the FPA component is not open source so it will take about 1 minute to do a sweep. You want full duplex if you are working with frequency hopping. It has 2 TX and 2RX channels.
- HackRf One – This is an amazing device. It goes from 1hz – 6ghz but its half duplex. With a down convertor using a hot wheels radar gun component you build you can get it up to 10ghz. Its FPGA device is open source and it can do a sweep in about 1 second. If you do a software sweep it will take about 90 seconds. This device also works with the Opera Cake used for Pseudo Doppler Triangulation.
- Blade40x – This device is nice because it’s full duplex but it doesn’t have as many channels as the lime sdr and its allot more expensive. I do not know the sweep rate for this device.
- RTL-SDR – This is the cheapest device it has a small range but you can pick one up for only $10 it allows you to get your feet wet with SDR and its the most compatible device out there besides the hackrf. You can not transmit with this device you can only receive on 1 channel.