I've retested the microwave, using a 4th gen ipod touch, with 2.4 ghz wifi only.

Just outside the oven, Speedtest is giving me 25ms ping, 10Mbps dl. Inside, with the door closed, it's getting 44ms ping, 1Mbps dl.

I used wifi, since that's what I have access to. Wifi is in the same (rough) band as microwaves. It's probable that the one I tested with was old and crappy with bad shielding. When it's running, it's noisy enough that it will tend to kick any wifi connection from the 2.4ghz into the 5ghz band.

(I live in the boonies, and cell signal is 0 bars till I get out to the road, and even there I really only get texts)