Two interesting videos on hum with AM transmitters

I watched them both when you posted, meant to comment then but got sidetracked. I recall I was initially surprised when unhooked from the AC and powered the transmitter with a battery and it still exhibited the same hum. There was something else that jumped out at me too -but forget what it was, might watch it again.

But as for Sean Cuthbert's transmitter, the same used in the demonstrations, and also his processor - both of which discussed here for a while years ago.. both still available. They use to get a lot of fanfare. Don't hear much about them anymore. @Mark I think you have the Sholckwood now but didn't you use to use the Cuthbert processor?