Lumpy wrote:
. . .
Station is "backyard remote", battery powered,
asymmetrical wire dipole.

I found some recordings of electric blanket
noise via k0bg's site. It sounds very much
like those recordings. Both of the elec blankets
in my home are off and unplugged. Neighbor elec
blankets? They would be probably 100' away from
the closest point to my antenna.
. . .

If you're using an asymmetrical dipole, the feedline is very likely a
part of the antenna. So the source of the noise or the conductor which
is radiating it might be closer to the antenna than you think.

Roy Lewallen, W7EL