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SDR

From dankwiki

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?
RTL-SDRv3 R820TR2 2.4 sustained
3.2 peak
8 25--1750 No No
NooElec NESDR
SMArt
R820TR2 2.4 sustained
3.2 peak
225--300kHz
.9--2.56MHz
8 25--1750 No No
NooElec NESDR
SMArt XTR
E4000 2.4 8 65--1100
1200--2300
No No
HackRF One RFFC5072 20 2--20 8 1--6000 Half No
AirSpy R2 R820TR2 10 2.5--10 12 24--1800 No No
AirSpy Mini R820TR2 No No
AirSpy HF+ DC--31
60--260
No No
BladeRF 2.0 micro AD9361 56 61.44 12 47--6000 2x Cyclone V
BladeRF x40/x115 LMS6002D 28 40 12 300--3800 1x Cyclone IV
Ettus B210 USRP AD9361 56 61.44 12 70--6000 2x Spartan 6
XC6SLX150
Ettus B200 USRP AD9361 56 61.44 12 70--6000 1x Spartan 6
XC6SLX150
Per Vices Noctar 250 125 12 / 16 DC--4000 1x Cyclone IV

Software