[Lowfer] Slow risetime, wide squarewave at approx. 137.7 kHz

[Clint Turner]

I've seen it before in the past couple weeks - and it appeared again 
tonight:  I see an "almost" square wave pattern that goes from about 
137.665 kHz to approx. 137.712 kHz.  Unfortunately I don't have captures 
of its previous appearance - but I've set up captures to run overnight 
this time.

Tonight it seems to be spending about 16 minutes or so at the upper 
frequency and then changing - in steps - over a period of 3-4 minutes to 
the lower frequency, but I'll have to see if I can get more captures of 
it before I can better-characterize its timing.  Unfortunately it seems 
to have taken a bit of a QSB at around 0557.  Its frequency reference 
appears to be very stable and the frequency jumps are well-defined.  I 
looked to see if anyone else is "seeing" it, but it's below the normal 
frequency range of the '137 kHz grabbers that I know about.

Anyone know what this thing might be?

Clint
KA7OEI/CT