[RFI] Ugly noise environment

Pete Smith N4ZR n4zr at contesting.com
Wed Feb 24 17:26:50 EST 2016


I recently relocated temporarily to an urban apartment in Towson, MD.  I 
set up my active vertical antenna outside a window, and was really 
surprised by how high the noise level is.

I've put an SDR view of about 200 KHz at 
<https://www.dropbox.com/s/op4t1wa8erk5k7v/Noise%20signature.png?dl=0)>.  You'll 
notice that the  noise floor at 14 MHz is around -100 dBM, compared to 
-120 at my rural QTH, and at some other frequencies the noise floor is 
as high as -70 dBM.

I'm used to line noise, but the thing that strikes me about this is the 
noise peaks that occur every 60 KHz. On AM, they sound like arcing, with 
a pronounced buzzing sound.  There's also a "meta-period" to the noise - 
it is much worse at some frequencies than others - there are very broad 
noise peaks at around 5 and 10 MHz, and "valleys" at 14 MHz and elsewhere.

Does anyone have any ideas from this "signature" what I might be dealing 
with here? I'm in a bit of a "stealth" situation here, which tends to 
put a crimp in any thoughts of DFing with a VHF receiver and my 136-MHz 
Moxon.

-- 

73, Pete N4ZR
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