Re: [Discuss-gnuradio] Passive radar using my hacked dual coherent channel rtl_sdr dongle

[Jared Clements]

Since they're clocked together I would assume that your alignment would consist of interpolation on the primary FM signal, what do you do to remove it later?  If your code is too messy to release can you share a block diagram?

Thanks,

Jared

On Sep 26, 2013 7:21 PM, "Juha Vierinen" <address@hidden> wrote:

Hi,

I'm just using a simple script to dump data to disk. I then have another program that analyzes the files. It is not too complicated. The measurement equation is a convolution with the assumption that the target is stationary over ~20 ms and that the ground clutter is stationary over ~1 second. 

My code is a mess at the moment and it depends on other unpublished libraries that I have written, which are also a mess.  I might release this once I have cleaned it up a bit. 

juha

On Thu, Sep 26, 2013 at 9:00 AM, M Dammer <address@hidden> wrote:

This is awesome. How did you analyze the data ? Is the software/source (both grc setup and data analysis) available ?
Mark

On 25/09/13 23:23, Juha Vierinen wrote:

I hooked up my dual coherent channel rtl_sdr dongle into two of our passive radar antennas that we have here (log-periodic antennas pointing North and South). After fine tuning gains and signal levels, I acquired some FM radio data (WWLI 105.1 MHz). To my surprise, I got passive radar echoes from airplanes when I analyzed the data. Passive radar is one of the most challenging types of radar because the requirements for dynamic range are larger than those for eg., pulsed radar, I really didn't expect much from my test. 

I expect the $16 system to also be able to see specular meteor echoes (typically stronger than airplanes) and ionospheric field aligned irregularity echoes. Not bad for something that required about $10k-$100k investment in a digital receivers ten years ago, and a $2k investment yesterday. 

Visually, the rtl_sdr dongle system has a little bit more noise than the usrp n200 with a tvrx2. And also, there is the hassle of aligning samples. So I would still use the usrp if given a choice, as it does perform better and requires no hacking.

Here is the passive radar video I just made using my $16 dual channel rtl_sdr (the timestamp is broken, but I just did the measurement an hour ago):

http://youtu.be/KRqtqtCVRR0

For comparison, here is an example passive radar video of airplanes and specular meteor echoes done using a usrp n200 + tvrx2. This was earlier, so the targets aren't the same:

http://youtu.be/-k2ZuhAz0ac

Does anyone know who manufactures these dongles, or who designed it?

PS. I ordered a seven port usb hub, in anticipation of adding more coherent channels (to do interferometry and maybe imaging). It seems that every time I browse ebay, I end up ordering a few dongles. 

juha

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