Sniffing out man-made HF noise (updated)

Since  this summer, my hobby is at times made impossible because of intermittent 9+30 dB interference on all HF bands. When present, those strong fields are making  contacts virtually impossible. Because of the intermittence, it is difficult to locate the source. This morning, I decided to go for a neighborhood walk with a borrowed Sangean portable shortwave AM/SSB receiver (thanks, Boudewijn PD5WO) with headphones. Two, possibly three high level noise sources were identified, a restaurant, 30 meters away using PLC (aka Homeplug) equipment and even further down the street I found fluorescent signage of a snack bar causing enormously strong and constant broadband HF noise. Switching off the FL tubes made background noise drop several S points on 40 meters in my shack. The PLC’s are a different story altogether, those devices are a true nightmare for radio hams. In my case, a 30 Mhz wide +30dB rattle is present when data is being transferred between those devices. But I’m glad the search with a simple portable radio was fruitful and hopefully the owners of these PLC flamethrowers will cooperate in finding a workable solution for all parties involved. To be continued.

UPDATE Nov 20: I made a video of the intermittent interference and further investigation has sourced this noise to the Cafe next door. Will update when we located the culprit inside, I need assistance from the owner which I hopefully will get over the next few days. Will update when we found it. The owner of the restaurant with PLC’s has agreed to my proposal to replace them with a cat5e cable which I will provide and install for free. 

UPDATE Nov 29: FOUND IT. See this followup post

The noise disappears at the 53 seconds mark and reappears 50 seconds later, lasting over 5 minutes.