Build a Passive Radar With Software-Defined Radio

upstart writes:

Spot stuff with the KrakenSDR and two TV antennas:

Normally, when it comes to radio-related projects, my home of New York City is a terrible place to be. If we could see and hear radio waves, it would make an EDM rave feel like a sensory deprivation tank. Radio interference plagues the metropolis. But for once, I realized I could use this kaleidoscope of electromagnetism to my advantage-with a passive radar station.

Unlike conventional radar, passive radar doesn't send out pulses of its own and watch for reflections. Instead, it uses ambient signals. A reference antenna picks up a signal from, say, a cell tower, while a surveillance antenna is tuned to the same frequency. The reference and surveillance signals are compared. If a reflection from an object is detected, then the time it took to arrive at the surveillance antenna gives a range. Frequency shifts indicate the object's speed via the Doppler effect.

I was interested in passive radar because I wanted to put a new software-defined radio (SDR) through its paces. I've checked in with amateur SDR developments for IEEE Spectrum since 2006, when SDR became something remotely within a maker's budget. The biggest leap forward happened in 2012 when it was discovered that USB stick TV tuners using the RTL2832U demodulator chip could be tapped to make very cheap but effective SDR receivers. An explosion of interest in SDRs followed. [...]

I was researching diving back into SDR with one of these devices when I spotted the CrowdSupply campaign for the US $399 KrakenSDR. It's receive only, but it boasts not one or two tuners, but five! The tuners are based on the RTL R820T2/R860 chip, and they are combined with hardware that can automatically do coherence synchronization among them.

Read more of this story at SoylentNews.