[RFI] any ideas on this one? all gone...

Sat Nov 17 11:56:42 EST 2012

Well, got a call last night from the owner and met him there this morning...
but the noise was already gone when I got there.  he did turn back on a
couple things that they had turned off in the morning, but it didn't come
back.  They did have a friend who had been there for about 6 weeks who just
left, hopefully whatever it was he took it with him.  But at least they were
cooperative, and I have their number if it comes back!

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net

-----Original Message-----
From: K1TTT [mailto:K1TTT at ARRL.NET] 
Sent: Saturday, November 17, 2012 12:07
To: rfi at contesting.com
Subject: Re: [RFI] any ideas on this one?

I did some more analysis of it today and left another note for the
homeowner... may post screenshots and data on web page later.  I put a
better antenna on my qs1r and upped the rate and it looks like it is
sweeping across that about 50khz frequency range.  I also looked in more
detail at the screenshots of the harmonics of it I was seeing and did some
calculations and came up with an interesting pattern, then went and did some
more measurements sitting under their power line with a non-resonant shorter
antenna.  What I see is the noise repeating over the following (approx.)
frequency ranges:


Lots of odd harmonics... might make a nice square wave at 100khz or so.

It would seem that the weaker images I was seeing previously on even
harmonics were probably from overload of the sdr-iq as they were clearly not
easily visible today... or it could just be that the smaller antenna wasn't
sensitive enough to make them easily visible, but as I stepped up the
spectrum in 100khz steps it was obviously there every other step... that
would mean to me that if there are even harmonics there were probably at
least 30-40db down.

I stopped there because what I had seen at home was that the harmonics died
out before 3mhz so were no longer interesting... but now that I know the
pattern I can hear it on the south and east beams of my 4-square on 80m
below 3500, from about 3600-3700 and from about 3800-3900khz.  

-----Original Message-----
From: Jim Brown [mailto:jim at audiosystemsgroup.com]
Sent: Sunday, November 11, 2012 22:52
To: rfi at contesting.com
Subject: Re: [RFI] any ideas on this one?

On 11/11/2012 11:09 AM, K1TTT wrote:
> 160m noise, 50khz wide, very sharp edges and stable frequency. 
> recordings and spectrum images at:

Hi Dave,

There seems to be some sort of modulation on it -- is that dithering, or
might it be a Plasma TV?  Just wild guesses.

73, Jim K9YC

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