There’s a hole in the corner of the ceiling where a telephone extension used to go into the loft in order to route its way ultimately downstairs. I think that hole has just become a 5A mains supply conduit!
The 1090Mhz filtered preamp is this one by Uputronics. This one is the SAW filter model, they have a more expensive ceramic filter model. It can be powered either by mini-USB or by bias tee through the coax. In that pic it’s being powered with a 0.5m USB lead from one of the Pi’s USB sockets. It works really well and I’m pleased with it.