We had a specific lounge chair, which when you sat in it with a laptop, if someone was using the microwave, the wi-fi would drop out. If you stood up, everything was fine. We took that lounge suite to the holiday house. Good riddance :)

It's almost certainly a microwave or cordless phone. I still forget sometimes and knock out my own wireless with a microwave.

It's definitely not mine. The effect is crazy tho. I wanna at least find a way to find the source/direction of it.

apt-get install wavemon

I love that tool. Tells me signal strength and quality (i.e. how much noise there is). Actually, opening it now, I see there has been an update and it has gained two new indicators. Used it multiple times to find APs. Also works on laptops (though a smartphone is much more handy to walk around with).