[Elecraft] K3/100 -Second floor- no RF ground ??

[N4CW at aol.com]

IMHO, the real problem is the location of the r.f. and not the ground. My  
shack is also on the second floor and I NEVER have problems with r.f. in the 
 shack, even with high power.
 
I've also done attic and gutter/eaves antennas, and they've ALWAYS managed  
to couple into house AC and telephone wiring. If you have absolutely no 
choice  but to keep the antennas hidden (in or on the house), then
you MUST decouple the antenna from your feedline. You can use lots of  
ferrite beads on the existing feedline, close to the antenna. If you have a  
current balun, use that in place of the center insulator.
 
But if at all possible, go outside the house...preferably, away from  it!
 
Good luck,
Bert, N4CW