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:

Driveby System - 44.485 Mhz

This morning I was hunting around for the source of some power line noise that plagues me while I was still at home (before taking the Driveby System back on the road today).

Above is a video of what I 'finally' found.  (not sure why I didn't really search for this years ago).  Anyway I use HDSDR at home as a "pan adapter" for my large radio which is connected to my 57 foot long 10 element 50 Mhz yagi.  I've been hunting for a way to be certain that the noise I'm hearing *IS* power line noise.  One way I've read about is to analyze the AM audio and look for FFT spikes that are relative to 60hz increments.  So this would mean that you would see (possibly) 60hz, 120hz (definitely), 180hz, 240hz and so on when you analyze the audio from the AM signal.

Well guess what?  I already had been using a tool that could do this "HDSDR".  So with the pan adapter setup I use for my large ham radio the 9 Mhz IF output to a Nooelec "Ham It Up" HF to 125 Mhz up-converter.  Then I configure HDSDR to look at -134 Mhz.  Which puts me zero beat on the frequency in HDSDR that I'm trying to SEE visually.

Anyway...long story short.  I found something very interesting this morning.

Between around 44.235 Mhz and 44.6 Mhz (the best centered freq seems to be 44.485 Mhz) there is an EXTREME signal LOADED with power line BUZZ/HUM.  Looking at the Audio analyzer in HDSDR (lower FFT display on my screen in the video) you can CLEARLY see the 120hz, 180hz, 240hz .... spikes.

Knowing the actual center frequency of the Arcing noise source REALLY helps!  With that information I can program the frequency into and RTL or my Walkie-Talkie like HT (VHF/UHF handheld radio) capable of AM, FM, WFM reception.

I'm planning today to use the 49 Mhz RTL graph and mapping to be re-coded to use 44.485 Mhz.  because of what I've found this morning.  After I've mapped that all out I'll present it here as an update to this blog entry.

This signal is approximately in the 300-335 degree azimuth from my tower.  Here is a map of that area.

Also see a followup remapping post HERE.

(click image to see larger)

FOLLOWUP UPDATE:

After driving around with just my HT radio and a tiny whip antenna I'm pretty sure I've spotted the worst of my noise sources.  It's located just behind a local middle school.  And the source pole was actually within about 6 feet of where I suspected the noise has been coming from.  As noted earlier this morning (see red line above map).

This map shows the location of the pole which you can see via satellite image.

(click image to see larger)

!!! THIS IS THE POLE !!!

WTF ?

Um 2x WTF !!!  Notice the school, Notice the Fence, Notice this dangling Loose Ground wire is within reach of any stupid Middle-School Child that reaches for it?

Now check this out! Driveby confirms!