This signal has been up and cycling since before 0200z this evening, and was up also last night.
Tonights cycle is 5 minutes off air, 5 minutes of dead carrier, 5 minutes off air, 5 minutes of LFMCW waveform, repeat cycle starting with 5 minutes of dead air. Last night it used both this cycle and a 10 minute on/off cycle.
While it is currently on 5120 kHz center freq, earlier tonight it was on 5100 kHz center freq. The LFMCW waveform has been anything from 25 to 60 kHz wide, picking one width during any given 5 minute active cycle. Sweep rates from 1 Hz to 40 Hz have been seen, like width only one sweep rate per transmission cycle, mostly 25 Hz and 1 Hz.
This could be an OTHR, the LFMCW waveform is a common one for them. However the CW mode is not something an OTHR would use for much. If HAARP was still active I would say that would be a good candidate for the source, but last I heard the transmitters would not be ready to come back online for several months. Maybe they are testing them early?
The carrier has 60 Hz hum on it, showing clear 120 Hz, 240 Hz, and 360 Hz lines. So wherever the source it is most likely using 60 Hz power.
I do not have a good direction for source yet, but because of times I can receive it and normal propagation I would guess west coast of North America, or maybe in the eastern Pacific, but not sure who it would be there.
T!