thank you for that quick, informative response....hopefully I won't get too winded here, but 3 years ago a multiplexer which was part of my security system was polluting my entire property with a very loud hash noise...+40db...wiped out everything, all bands,.....once that was removed from the system, all that knocking hash disappeared....still in the system though was, [lacking a better word] a 5-7 db of a swirling noise.....tried a best selling AC in-line suppressor which reduced the noise about 3 db, but still there [+4 db]..[probably whatever the local cable company was/is using to provide internet access is causing that problem because the power company was here and cleared themselves...lol..
Finally I switched to battery power [off the grid completely]....noise was virtually eliminated .. maybe .5 to 1 db atmospheric [these readings were all in the yard or in an extension room out back]....but whenever I take these radio's into a room upstairs [on battery power], whether a computer is in the room or not, certain sections of the rooms generate some heavy noise....20-30 db mainly 40 and 80m......
So what I did was I took the Icom to the noise free room in the back of the house.....I then ran a 30 foot USB extension cable to the computer upstairs.....without the usb cable even plugged in to the computer, immediately plugging the usb cable into the rig brings the noise back to +10db......the guy at Icom said the 30 foot long usb cable was probably picking up noise acting like an antenna....all that being said, will your suggestion of clamp-on ferrite cores for RFI suppression do the trick?....if so can you be specific on model numbers and actual placement of these things...sorry to say I have NO experience with the cores, which you are probably already aware of.....
thanks so much!