Sparse Array Beamforming with a Phase Coherent 21-Channel RTL-SDR Array

Radio Direction Finding came up the other day, and that's one of the uses for something like this. Along the same lines, there is a project out there to provide an "off the shelf" coherent RTL-SDR receiver array:

https://www.crowdsupply.com/krakenrf/krakensdr

That being the successor to KerberosSDR:

https://www.rtl-sdr.com/ksdr/

Looking forward to getting my hands on a KrakenSDR later this year, hopefully.

To me the most interesting part of the paper was how they synchronize the streams from multiple receivers (they inject a common noise signal to all receivers and then align the individual streams using cross-correlation).

> It was also observed that the relative phases of the signal streams drift slowly during the operation.

This is an interesting observation. If they are running all RF PLLs from a common reference clock, and the PLLs remain locked, there shouldn't be any long-term drift.

Years ago I saw an interview with the guy who founded this website. It was at some ham meetup. I have looked around and can’t find that interview anymore. It was originally on YouTube… does anyone know the video I’m talking about? He specifically talks about learning that you can do anything you put your mind to after his MIT Phd.

Great work. Back when I worked on DFing, ESPRIT was my favorite estimation algorithm. If I remember right, it was slightly less accurate but much more efficient than MUSIC.