Just some comments on common household noisemakers at LF that you may not have noticed. First, I have no "official" internet service out here in rural Texas. I access the internet using a "hotspot" set up on my phone. That connection is also the way I upload wspr spots as well as access this forum. To the point of this post... I need my cellphone on since my radio activities would not include signal reports on the 'net without it. Now the problem...I use an android phone and have noticed that the charger for the phone generates rf trash onto the LF spectrum when plugged in... raising the noise level. I had found, by trial and error, that the "white cube" charger issued with Iphones does not have this rf issue. I bought one of those cubes and that rf issue went away, thank goodness. Now...
My second tablet pc is an Asus and uses an android 5V wall wart to power it... same rf issue. Can't use another Iphone charger... not enough current capacity. Generic Wireless phone chargers also add rf trash into the LF spectrum... a little when there is no phone resting on it, a lot more when the phone is on it charging. Found that out when I bought one to see if it would bring some relief... it didn't. I also need and use a powered usb hub that provides 5V to my main pc sdr as well as other rf devices needing same. It adds noise since the hub distribution box is powered by a higher current wall wart "switcher". All these devices use a two-prong 120v cord, which of course, provides no ground path from the devices to electrical ground.
To keep costs down, all these consumer devices are quite noisy at LF. No one that makes these, nor the FCC cares, because 99.9 % of consumer users aren't LF radio enthusiasts.
It would be REALLY nice to have a CLEAN LINEAR 5V power supply that had enough current capacity and multiple usb output ports to power all these devices. I'm pretty sure my rx reports would improve by a substantial amount. I'll be checking into this possibility... but probably be more money than I want to spend on it.
Just a little venting and rambling...
Ray