I got one of these;
View attachment 71300
and tried it on my SDS200, and wow, it just knocked the whole VHF/UHF and up spectrum down from 7 db to about 11-12.
I hoped it would help, as there is a local FM station that causes hash on some radios, and knocking down HF might help too. It was so bad, I verified how much it affected signal strength by plugging it into a Spectrum Analyzer and then my antenna (Just a whip about 18" long) and the only place it had a 1 db loss was in the very low Aircraft band around 115 MHZ. By 138 MHZ it was down about 8db. At 800 MHZ, it was down 12db. Now I need to find my Par filter I misplaced when I moved, and see what that can do. I know it works as advertised. I think I'm going to open up the HPN-30118 and see if something wasn't soldered inside.