I have been monitoring the lower end of 10M quite a bit lately. It is such a pleasure to see the band so wide open for a change.
There seems to be a fair bit of intruders in the band. The most noticeable, are the signals that sound like foghorns. The signals all have the same signature and sound similar. They seem to have unstable oscillators. At the start the transmissions the frequency changes fairly rapidly then settles down to a fairly stable tone. For example 500 Hz in screenshot below. Some have a single letter indent; some have two letters and some none at all. I suspect the signals are from the infamous beacons associated with the marker buoys used by the long line fisherman.
They seem to be spread out over the entire 10M band.
The screenshot below was taken on 28.036.00 MHz, CW @ 13:12 UTC
I suppose these signals are being observed worldwide?
73, Pierre ZS6A