[tknkx]

In the context of this article, having eight houses to check is soooo much better than having absolutely no clue. If it's not a malicious actor, you'll find out what's emitting the signal in a matter of an hour tops. Being able to do that using a $10 device from ebay is fantastic.

[megaremote]

Ok, you have 8 houses to check. What do you do now?

[tknkx]

You knock, explain the problem, ask if they've installed new electronics lately, especially remote controlled/domotics stuff. Repeat until you get a satisfactory answer. Chances that you will get one are very high.