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SDR

From dankwiki
The SDR software stack, at least according to PothosWare (authors of SoapySDR)

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 rtl8xxxu
blacklist dvb_usb_rtl28xxu
dank@vespula:~$ 

note that users of initramfs might need to rebuild or modify their initramfs to include this file.