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[RFI] 120Hz period noise ID

To: rfi@contesting.com
Subject: [RFI] 120Hz period noise ID
From: "Leigh L. Klotz, Jr." <Leigh@WA5ZNU.org>
Date: Fri, 26 Oct 2007 20:56:21 -0700
List-post: <mailto:rfi@contesting.com>
I have a buzz that happens some, but not all, nights, and not during the 
day, at least so far.
On HF, I can hear it 80-20; I haven't tested other bands.

Here is a screenshot of what it looks like in an SSB receiver:

The axes are in ms, and the period is close enough to 120Hz that I think 
that's what it is.

Here's what I've done so far:

1. Rotated a 20m beam and found the general direction, with about a 35 
degree beamwidth.
2. Used a simple wire loop on a TH-F6a set for AM on ~5Mhz and found 
it's not coming from my house.
3. Found a strong buzz coming from the sodium vapor light in front of my 
house, but it could also be just coupling from the light mast as an 
antenna (same effect for WWV on 5 MHz).
4. There is no correlation between the sodium vapor light being on or not.
5. I haven't heard it during the day.
6. I haven't heard it every night.
7. There are other power lines around in the general direction.
8. I've been able to hear it from the light mast on 135Mhz but the wire 
loop isn't sensitive enough to find it at a distance; I will probably 
make a wire yagi if I need to do more looking.

So, does this look like power line noise?  Or should I be looking for 
something in a neighbor's house that they use at night that also somehow 
emits broadband noise with a 120Hz period?


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