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SDR
Software-defined radio moves the majority of radio processing into software, facilitating relatively inexpensive wide-band hardware interfaces to the electromagnetic spectrum, especially those frequencies below 3GHz. Pairing advanced SDRs with software-defined antennas yields dynamically optimal cognitive radio. Perhaps most famously, DVB-T television tuners built around the RTL2832U chip, and available in USB form factor for less than $30 (particularly the Rafael Micro R820T2), can reliably provide 2MHz of RX bandwidth anywhere from ~30MHz to ~2GHz (still lower frequencies are supported via direct sampling). For $500, powerful units capable of tremendous bandwidth and range (as well as transmission capabilities) are available, and from there it's not that great a leap to building your own stingray--if the cops have 'em, so should you, doyouknowhatiamsayin?
On the more ballin' end of things, a tricked-out Per Vices Cyan will run you $290k before shipping.
Hardware
| Device | Tuner | BW (MHz) | Samples (Msps) | ADC | Tune (MHz) | Xmit? | FPGA? | MSRP |
|---|---|---|---|---|---|---|---|---|
| RTL-SDRv3 | R820TR2 | 2.4 sustained 3.2 peak |
8 | 25--1750 | No | No | $20 | |
| NooElec NESDR SMArt |
R820TR2 | 2.4 sustained 3.2 peak |
225--300kHz .9--2.56MHz |
8 | 25--1750 | No | No | $20 |
| NooElec NESDR SMArt XTR |
E4000 | 2.4 | 8 | 65--1100 1200--2300 |
No | No | $35 | |
| SDRPlay RSP2 | 10 | 12 | DC--2000 | No | No | $170 | ||
| SDRPlay RSP1A | MSI001 | 6 | 14 | DC--2000 | No | No | $100 | |
| HackRF One | RFFC5072 | 20 | 2--20 | 8 | 1--6000 | Half | No | $300 |
| AirSpy R2 | R820TR2 | 10 | 2.5--10 | 12 | 24--1800 | No | No | $170 |
| AirSpy Mini | R820TR2 | 12 | 6 | 12 | 24--1750 | No | No | $100 |
| AirSpy HF+ | 0.768 | 16 | DC--31 60--260 |
No | No | $150 | ||
| BladeRF 2.0 micro | AD9361 | 56 | 61.44 | 12 | 47--6000 | 2x | Cyclone V | $480 |
| BladeRF x40/x115 | LMS6002D | 28 | 40 | 12 | 300--3800 | 1x | Cyclone IV | $420 |
| Ettus B210 USRP | AD9361 | 56 | 61.44 | 12 | 70--6000 | 2x | Spartan 6 XC6SLX150 |
$1100 |
| Ettus B200 USRP | AD9361 | 56 | 61.44 | 12 | 70--6000 | 1x | Spartan 6 XC6SLX150 |
$675 |
| Per Vices Noctar | 250 | 125 | 12 / 16 | DC--4000 | 1x | Cyclone IV | $2500 |
Software
The Linux SDR software ecosystem is robust, but complex. There are multiple middleware layers available, providing generic access to various hardware devices; many user-exposed applications support both middlewares, sometimes in addition to their own native hardware support. As a result, there can be multiple ways to specify a given piece of hardware in a particular tool.
Kernel
At the lowest level live the various driver libraries for SDR hardware. It is atypical for SDR hardware to require (or provide) a Linux kernel driver; most appear to be implemented wholly in userspace atop raw USB devices. Indeed, the primary interaction most users will have with their kernel might be removing (and possibly blacklisting) the dvb_usb_rtl28xxu DVB driver autoloaded for the RTL-SDRv3 USB dongle. This driver prevents the RTL from being used with rtl_sdr, the userspace RTLSDR libraries. To blacklist it, create an entry ending in .conf in /etc/modprobe:
dank@vespula:~$ cat /etc/modprobe.d/blacklist-rtl8xxxu.conf blacklist dvb_usb_rtl28xxu dank@vespula:~$
note that users of initramfs might need to rebuild or modify their initramfs to include this file. Adding a blacklist entry does not remove a loaded module; for that, use rmmod dvb_usb_rtl28xxu.
Userspace drivers
| Family | Software | Source | Tools |
|---|---|---|---|
| RTL2832U | rtl-sdr from OsmoCom | https://github.com/osmocom/rtl-sdr.git | rtl_test, rtl_sdr, rtl_power, rtl_tcp, rtl_fm, rtl_eeprom, rtl_adsb |
| HackRF | libHackRF from Great Scott | https://github.com/mossmann/hackrf.git | hackrf_cpldjtag, hackrf_debug, hackrf_info, hackrf_spiflash, hackrf_sweep |
