In my quest to reduce the S7-S9 band-wide QRN at my QTH, I just made an important discovery!
My house on the outskirts of Luang Prabang has a garden where I erected my quarter-wave fan wire verticals for each band, (top band has a loading coil), and I use either 32 ground radials or 2 tuned elevated radials for each band. I've been trying all sorts of ground/antenna systems to reduce the noise level on receive. Magnetic loop, pennant antenna, MFJ noise canceller etc - nothing reduced the back ground noise level at all.
There is a 3 phase transformer 50 metres away and 220 volt 3 phase cables on 2 sides of my property. My transmit signal gets out well! But especially on the low bands, the stations that hear me (and call me), are lost under the S7-S9 noise...
I tried powering my rig from a car battery = no reduction in noise level.
With the rig powered from the battery, I switched off the 220 volt mains supply to the house and everything in it, and powered off my UPS that I use for my wifi routers. The noise level stayed the same!
I've used a 'sniffer' to look for noise sources, but it's wideband, presumably coming from the power lines on 2 sides of the house.
Today, I took my rig down to my antennas, (about 25 metres away from the house and perhaps 15 metres away from the nearest power line), and powered the rig from the car battery, and connected it to my antenna feed point.
WOW!! The background noise level has dropped on all bands to about S1 - S2!! Signals are booming in

So why is the noise level so high in my house, with everything powered off, common mode choke on both ends of my coax feedline? How is the noise getting into my rig, even when it's powered from a battery? I'm stumped!!
..... stumped, but also very happy that the noise level all but disappears when I use my rig next to my antennas.
So.... since I don't really want to play DX in a tent camped by my antennas in the garden, what's the best way to eliminate the noise that gets into my rig when it's in my house?
The only solution that I can think off is to place the receiver inside a faraday cage, with just the antenna cable and power lines/battery line coming into the cage.
I would appreciate your suggestions!