Here is an RFI story with a happy ending. My neighbor installed low 12 volt lighting. When he turned it on it made S9 noise on my receiver from 5 to 20 MHz. I met with him and after working for a couple of hours on locating the source we finally found it. It was a very small switching power supply. Here are some pictures:
This is a small 120/12 volt 75 watt supply.
This is the name plate of the noisy supply.
Here is the choke after 22 turns of #14 (2 wires).
Here is the 42 turn choke wired in at location 1.
This is a second choke wired in at location 2.
Here is the back yard and pool.
The yellow stuff on the ground is amdro because there were fire ants at location 2. The noise was S9 before the chokes were installed. After the chokes were installed the noise is still there but its low, just a little above the daytime background noise on 5 - 20 MHz. My neighbor will run the lights at night when the noise on the band is so high I will not hear the noise at all so there should be no problem - case closed. The neighbor was very cooperative.

The chokes I used are Amidon 2.4 inch toroid , either number 43 or 77 material. Look under ferrites for RFI. I think they are about $9 each. An order can be called in and ordered with a credit card.

73 de k5gp, Gene