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Very Strange Alarm Noise

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PresentedIn4D:
http://www.youtube.com/watch?v=vxcB9YMMjQQ
What could this possibly be? I'm currently in Jacksonville, FL, and this is the first time I have ever heard this. Is this just some sort of beacon, or something different? Thanks.

SW-J:

--- Quote from: PresentedIn4D on August 16, 2010, 0104 UTC ---http://www.youtube.com/watch?v=vxcB9YMMjQQ
What could this possibly be? I'm currently in Jacksonville, FL, and this is the first time I have ever heard this. Is this just some sort of beacon, or something different? Thanks.

--- End quote ---

I don't detect much fading on the signal (that may be a little difficult to tell from the recording on my end though). Fading, to put it succinctly, means distance.

If it's present with the same signal strength 24 hrs a day it's a) probably something in the house or b) probably something in a neighbor's house.

Edit: Spelling!

PresentedIn4D:

--- Quote from: SW-J on August 17, 2010, 1502 UTC ---
--- Quote from: PresentedIn4D on August 16, 2010, 0104 UTC ---http://www.youtube.com/watch?v=vxcB9YMMjQQ
What could this possibly be? I'm currently in Jacksonville, FL, and this is the first time I have ever heard this. Is this just some sort of beacon, or something different? Thanks.

--- End quote ---

I don't detect much fading on the signal (that may be a little difficult to tell from the recording on my end though). Fading, to put it succinctly, means distance.

If it's present with the same signal strength 24 hrs a day it's a) probably something in the house or b) probably something in a neighbor's house.

Edit: Spelling!

--- End quote ---
Hi,
The thing is, it is not 24/7. That was the first and last time I heard it. However, last night, I heard a signal on a lower frequency that was similar to this, but it had more fading, less clarity, ect.

SW-J:

--- Quote from: PresentedIn4D on August 18, 2010, 1355 UTC ---
--- Quote from: SW-J on August 17, 2010, 1502 UTC ---
--- Quote from: PresentedIn4D on August 16, 2010, 0104 UTC ---http://www.youtube.com/watch?v=vxcB9YMMjQQ
What could this possibly be? I'm currently in Jacksonville, FL, and this is the first time I have ever heard this. Is this just some sort of beacon, or something different? Thanks.

--- End quote ---

I don't detect much fading on the signal (that may be a little difficult to tell from the recording on my end though). Fading, to put it succinctly, means distance.

If it's present with the same signal strength 24 hrs a day it's a) probably something in the house or b) probably something in a neighbor's house.

Edit: Spelling!

--- End quote ---
Hi,
The thing is, it is not 24/7. That was the first and last time I heard it. However, last night, I heard a signal on a lower frequency that was similar to this, but it had more fading, less clarity, ect.

--- End quote ---


Let's analyze this signal as far as 'content'. It sounds kind of line-frequency related raspy, but let's run through the analysis and see what that shows.

Let's first take one 'rep rate' (repetition rate) of a group of pulses like this:


     


and then we will do Fourier decomposition (Fourier Analysis) which looks at the frequencies making up the signal.

When we do this in Sound Forge, we have this:

     


Notice we have this kind of relationship between spectral components and 60 Hz line related components:

Freq
 Peak  x60Hz
 ----  ----- 
 360     6
 900     15   15 x 60  Hz
 1800    30   10 x 180 Hz
 2700    45   15 x 180 Hz




I would have to consign this to the category of something line-related (AC power line related) ... could not of course say exactly what, but, probably not over-the-air mil or even civilian comms ...

PresentedIn4D:
Ah, well, that clears it up. Many thanks, very interesting. I would have never guessed to analyze it in that way. So, you're most likely correct, it must be civilian electronics.

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