Several people have commented that the 10m (28MHz) band is very active at the moment. Compared to my 80m dipole, a little dipole for 10m was not too much of a challenge.
The first thing I notice is that it's alive with quickly sweeping signals which I don't think are over the horizon radar of anything made by people.
Even in the middle of the day I can hear US stations piling on to DX stations that I can't hear. There's also some AM activity which doesn't sound like hams. I called CQ and got a reply from an Indonesian station that gave me a good report despite his local noise.
Very interesting patterns to be seen:
A commenter on YouTube suggested looking up Whistling Atmospherics for more information.
Sliding down to the old 27Mhz CB band shows that things haven't changed there. Stations seem to be yelling at each other or playing distorted music. There is sideband but also quite a lot of AM in use.
Here's a screen recording of me tuning around a bit using an AirspyHF+ remotely operated using SDR++ in server mode - which I really like.
It's an interesting band for sure. I now have a dipole for each of 80, 40, 20 & 10m. The antenna tree is looking rather busy.