Wednesday, January 21, 2015

Nice Power Line Noise Visualization - HackRF, SDR#, VAC, and Spectrum Lab

I wanted to get a real nice noise signature of the Power Line Noise issue here.  What I ended up doing was to use a Windows 7 machine (for a change).  I used the following:

  • SDR# 'sdrsharp'
  • HackRF One
  • Spectrum Lab
The newer SDR# includes and Audio FFT however, I'm unable to resolve how to alter the bandwidth of it down to < 1 Khz in audio frequency.  It seems STUCK at 0-18Khz or so.  This is too wide to be able to really see the 60hz spike and it's harmonics of 120hz 180hz, and so no.  They just don't even register in it's FFT for some reason.  SOOO....

Since the built-in Audio FFT doesn't resolve down to < 1Khz I setup trusty Virtual Audio Cable (I use line 2 for this, because other software I use uses Line 1 already).  So this pipes the AM audio out of SDR# via Virtual Audio Cable (Line 2) and then I setup Spectrum Lab to listen on that same VAC line.

Turns out this is PERFECT.  It's as good, but even better in that there's a TON I can inside Spectrum Lab, like line graphs, alerts, etc...for monitoring over long periods of time.

So here's a screen shot of Spectrum Lab (v2.78b25) setup to use VAC Line 2 (noted above) as well as SDR# below it.  

Look how simple it is to ID the 60 hz audio and it's harmonics.  Um....schweet.

(click to see larger)

I tried using GNURADIO and it's Audio Source, but damned if I can't figure it out on Windows.  It's fairly simple on Linux, but Windows is a different animal with GNURADIO.  Kinda of a let down.  It'd be nice to create flow graphs from my fancier/faster Windows machine that I could port over to my Linux machine and vice-versa but that's not happening.

Here's a few more views of that Spectrum Lab can do:

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