Interesting sound, it gets scaled out to cover more frequency

[Antennae]

 6999kHz   
0416utc
About 2 sec. long
Receiver mode: I don't know it looks asymetrical
California Coast
There I was, minding my own business when this thing blipped by.   It is about 10Hz wide, then it scales out to 15Hz wide.  Notice the line that doesnt scale is not in the center of the transmission.  I used this as the reference for what frequency it was on.

[Oliver]

Hello Antennae,
check this link.It may help to clarify the mystery.

http://www.hfunderground.com/board/index.php/topic,21508.0.html

[Token]

Has this repeated?  Do you have a recording?  The "lines" in it look like repetition lines, like sweep rates of on swept signal or pulse rates in a pulsed signal.

T!

[Antennae]

Oliver, thanks for the link, I didn't see it in the first section and didn't take the time to go over the second section but I did check the recording of illegal taxi drivers


Token, I haven't seen it since the first time.  I shut the computer off 10min after the first one so I don't know if it repeated after that.
What kind of recording are you looking for?

I can play back my SDR data and record the audio but I don't know which demodulation mode would be best.

PS, I'm looking at the picture on another computer screen and I can't clearly see the neat lines it makes so some people might be missing out.  It looks like a leaf rake. The individual tines spread out. 

[Token]

I can play back my SDR data and record the audio but I don't know which demodulation mode would be best.

USB, with as wide a filter as possible or until the entire signal is captured.  Just one little burst is all that is needed.  Uncompressed WAV format would be best if possible.

T!

[Antennae]

OK, after poking around my recording I found one more noise and then a weird phrase. It was all on 6999.3kHz LSB.  

So I recorded this in LSB.  First is the scaled noise, then some regular noise, then a weird phrase that sounds overmodulated.  Here's a link to the recording:

EDIT 5/9/15, I took down the recording because it was just some ham operator noise.