If you have a 6m yagi, and rig that listens on AM on 50 mhz, try rotating your 6m yagi and get a direction. Plot the noise levels on a polar graph and compare that to a google map for some ideas as to the location of the source.
It worked for me on my PLN. Turned out to be less than 1 mile away at 255 degrees. An arcing lightning arrestor which the utility changed right in front of me.
With RFI, in general, go by steps, as high in freq as you can, the closer you get to it, until you find the spot. My RFi was audible from broacast band up thru 50 mhz but just murdered the 160-80-60 m bands.
no directional antenna on 6 at the moment...sandy blew it to kansas
par endfeds for 40m & 20m, vertical with rigs auto tuner on 12 & 10, stacked ku4ab squalo's on 6 & 2m. noise is 20 over S9 across entire 40m band, S7 across entire 20m band, non-existant on 6m & 2m, and i'm thinking un-related on 12 & 10 'cause it's 'reasonable' during daylight hours & gone at nite. 20 & 40, the noise NEVER differs.
endfed antenna issues? or.....?