[RFI] New to list...

[Larry Parker]

Hi Dave,
My vertical antenna situation is similar to yours,my antenna was about 150 feet
from the house and on 80m the signal was +40 db  with peaks approx every
20khz. 
This repetiton continued below the broadcast band getting stronger as I 
came closer to the fundamental frequency.
My receiver stopped at 30khz so I couldn't hear the primary frequency ,
but the harmonics were a big clue once I put things together,
such as the times the noise was present.
The time periods were mainly when around the dinner hours and  after dark 
until 11 pm.
This led me to believe it was either lighting or an entertainment device such as a TV.
My weakness at first was , I did not  include myself as a possible source of the RFI.
A portable AM radio tuned to the high end of the broadcast band above 1700 khz.
was all I needed to find the source with a very short antenna.
Good Luck