When there is a triangle or R above the signal strength, it means "Network roaming". I assume a house means "Home Only roaming"? Check your network settings and see if it is on Auto or Home.
That means a range extender is close (within range), not that aliens are going to abduct you lol. I've never seen it pop up, but we don't have a lot of range extenders out where I live
This makes sense as (obviously) the signal drops to almost non-existent around that hill. Much like wifi, the network is available but requires authentication for connection.