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My Journey with SDR and the “Noise” In Our World November 15, 2015

Posted by Marty Wolfe in sdr, Uncategorized.
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Just got started experimenting with one of these inexpensive SDR devices.  You plug it into the USB port (preferably USB 2.0) and run some pretty decent free software.  Typically you can get these SDR devices for about $20 – $30 and they come with a small multi-band antenna.  What’s really cool is the wide range in which you can tune these devices and the ability to decode the huge amount of digital data being broadcast across the spectrum.

So I purchased one of these devices.. hooked it up to an existing mobile antenna I had for Ham Radio and could easily hear many local FM radio stations.. quite well.. it even decodes the text giving the name of the song.

Actually I got interested in this since there’s a real security issue here.  Many of the devices and appliances we have in the enterprise and at home are leaking a ton of EM signals.  It’s really fascinating to see these traditionally invisible signals and discern their meaning.  Thus the interest in all this SDR work.

Once I got started, I realized that my current setup really wasn’t good at picking up all the signals I really wanted to dig into, especially given all the trees that surround half my yard (… trees typically absorb high frequency signals).

I recently updated my setup with a better antenna, better antenna connectors, and some better cables.  Plus I downloaded some additional software to be able to track ADS-B transponder signals.

I thought I would start with listening to unique signals.. ones that are hard to actually hear, and ones which have to be decoded.  So I chose these ADS-B transponder signals which are broadcast directly from commercial aircraft.

Here’s the list of parts..

  1. An SDR dongle – the “RTL-SDR Blog R820T2..” got it from this link >> http://www.amazon.com/gp/product/B0129EBDS2?psc=1&redirect=true&ref_=oh_aui_detailpage_o07_s00
  2. A better antenna.. I bought a Diamond 130NJ “discone” antenna.  Wide band reception.  Bought it from DX Engineering.. free shipping.. was a competitive price >> http://www.dxengineering.com/parts/dmn-d130nj
  3. Really good coax.. as low loss as is reasonable .. I bought some of this 400MAX coax, better than RG216.. and I bought 50 ft.  Also from DX Engineering, since they let you construct the cable with a quick online tool.  Worked great.  Got N-connectors on each end, much lower loss than PL-259 or SMA.
  4. Downloaded RTL1090 software (http://rtl1090.web99.de) and Virtual Radar Server (http://www.virtualradarserver.co.uk).  There’s a great “installer” that you can download from the RTL1090 site that will configure nearly everything.

A good video on setup and configuration is here: https://www.youtube.com/watch?v=UT8LO7hM640

Here are some pics..

[1] Once I got all the setup complete, here’s a screenshot of tracking planes directly from their transponders on 1090Mhz.  You can see RTL1090 running in the foreground and Virtual Radar Server running in the background (doing real time display of planes being received):

SDR - ADSB - Tracking Software.png

[2] This is what the setup actually looks like.. you can see the 400Max cable snaking out the window frame.. it’s connected to a $20 RTL-SDR dongle (just to the right and below the laptop.. hard to see).  That all plugs into a very slow Acer laptop running Windows 10 plus Virtual Radar Server and RTL1090.

SDR - ADSB - Workstation.jpg

[3] I originally used an Amateur Radio dual band antenna.. typically used on your car with a magnetic mount.. that covers 440Mhz (70cm) and 140Mhz (2m) bands.  That worked “ok”, but then I purchased a Discone style antenna which has a very large coverage space.. like 20Mhz to 2Ghz.. it really worked well.  I haven’t mounted it permanently yet, so for now I let it sit on top of my car, only when I’m using it of course and not driving! (since it’s a decent ground plane).  Working well so far.

SDR - Antenna.jpg

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