Question - Is the Microwave and any related I.T gear on the same electrical supply circuit? If they are then that certainly isn't going to help any. If they are

Question - Is the Microwave and any related I.T gear on the same electrical supply circuit? If they are then that certainly isn't going to help any. If they are on separate electrical circuits (or it's not applicable) then do a search for a Microwave Leakage Detector (Hint - pay a bit more for it than the low end stuff on E-Bay). I'm not sure if those off the shelf detectors would be able to discriminate between a leaky microwave oven and a nearby Wi-Fi AP though. If you can afford about $300 you can buy a HackRF SDR and place the aerial along side the coax and turn the microwave on and off and see how much noise gets created. (Note the cheaper SDRs aren't able to tune up high enough to cover the Wi-Fi frequency range). Bonus of going this route is you get to have the fun of getting to use the SDR for all sorts of other fun things and the software produces a waterfall screen that is easy for non-techies to understand - e.g. No spike, m/w on, big spike, m/w off, spike gone. Alternatively if the Comcast guy is interested they normally have access to signal analysers.