pss,
and again the average, you have no idea why netgear extenders always, without exception, have average reading of 50% of signal. thanks JOe!
What does your graph tell you? If your average signal strength is 50% it should be bouncing up and down accordingly, reflecting some sort of local activity/interference/something.
(And you can't be specific about NETGEAR hardware without knowing what info other hardware generates under the same circumstances.)