Shoutout to the wireless tester I thought was pointless

My buddy had a similar wake up call last year. He was helping his cousin set up a home office in this old apartment, and the wifi kept dropping. Turns out the previous tenant had plastered over a bunch of old, buzzing fluorescent light ballasts in the wall. His little signal sniffer started screaming near the outlet, and they found the interference source behind drywall. He said it saved them from hours of blindly checking cables.