For a bit over a day, by AirPort Extreme has been much slower than usual. Over the past year I've had
lastTxRate pretty consistently around 250, which is close to the
maxRate I get (289). Lately though I'm getting values more like 130-170 — all day without ever going higher.
What factors can account for such a sudden drop in performance? What action can I take to get my rates back up?
OSX 10.10.3; Airport Extreme 802.11ac (7.7.3). I've tried restarting the AirPort, and powering off/on, as well as manually assigning channels. The AirPort has not changed location, nor have any objects between it and the devices where I'm measuring the signal. Moving closer to (leaving the room where I've always worked and moving next to) the AirPort does get the
lastTxRate back up to values I'm used to.
Here's what I see in iStumbler: