6927.9 kHz and 6929.1 kHz "ding" parallel channel markers 2345 UTC 01/26/2016

[R4002]

Hearing beeps on 6927.9 and 6929.1 every few seconds.  Close to noise level so not sure if I'm missing some of the beeps but the timing doesn't seem to be the same all the time.  When tuned in USB mode (right now tuner is set on 6927.0 kHz USB) sounds like two different tones going at the same time.  The frequencies 6927.9 and 6929.1 are where the dots are showing up on the SDR waterfall. 

[JCMaxwell]

I have it here too, R4002.

[R4002]

If tuned in at 6930 kHz LSB it (they?) sound like submarine sonar "pings"

[chucks]

01/27/16   0045z
parked the sdr on 6930  lsb a while ago to see if I could see or hear these two signals.
about 0044z I hear what sounds like  a spoon on a glass.
I have both signals rising up out of the noise and fading back.
the audio very clear and the signals visible on the water fall.
Interesting no ideal what they might be.
another mystery on shortwave will just have to follow them.

Chucks

[ChrisSmolinski]

This is Link-11, used by the military. It turns up on 43 meters fairly often.