[RFI] An interesting RFI "noise" on 40 meters

[Kenneth G. Gordon]

So, now I have a "new" one...at least for me. Some sort of 
weird-sounding, very unstable raucus oscillation sound. Appears about 
every 12 kHz from 7002 kHz to at least 7350 kHz, although that is as far 
as I've so far tuned for it.

Wanders back and forth at 2 to 3 kHz while it is on, then suddenly stops 
for up to 30 seconds following a slight "pop", then resumes. Seems to 
start out somewhat "quiet" then build in intensity over a period of about 
20 to 30 seconds.

Signal level is 10dB over S-9 throughout the entire spectrum. Normal band 
noise level during the day here is S-9.

Receiver is an FT-890 in USB mode. In AM mode, it isn't nearly as 
annoying, although still strong.

I have a short .WAV file of it if anyone would care to listen to it. I 
cannot find anything on the ARRL's sounds of RFI list to match it.

Ideas?

Ken W7EKB