Another tell-tale sign I typically leverage for a first-pass type of test?
Pull out cell phone, check signal outside room, then go inside room and shut door. What do those lovely "bars" do ?
If they crash down to " X " aka. no service ... Houston you are going to have a problem.
If they remain the same, RF (albeit diff frequency) is getting in and out readily. A good sign that you should characterize as Colin suggests to get an actual measurement.
JF