Using a RF Explorer, we were able to confirm that it was indeed coming from the highway, most likely traffic radar or radar jammers. My old office was right next to the US-101 highway in San Francisco and in addition to the Mad-Max like WiFi interference from other offices in the same building, we had interference in the rooms closer to the highway like our meeting room.

Unfortunately, the 2.4GHz band is extremely crowded and you have a lot of interference. Most digital signals are bursty, however, and a spectrum analyzer will only catch sustained interference from the likes of microwaves or poorly shielded electronics, so that limits the usefulness of one. A spectrum analyzer has no knowledge of the 802.11 protocols, it just measures electrical forces in specific frequency bands and plots it as a graph. Since those are not WiFi protocols at all, a network card will not be able to identify them, other than as noise measurements. It will identify things like interference from microwave ovens, radar, wireless PA systems, Bluetooth, wireless cordless phones (e.g. To elaborate on the difference, a spectrum analyzer tells you how much radio energy is being received as a function of radio frequency.

Best ios wifi analyzer