RSP1 SDRuno and external filters

[mark.]

Has anyone actually measured the signal strength of an FM Broadcast Band signal before images of that signal starts showing up all over the spectrum? Living at the outer edge of a large city I am within 3-5 miles line of sight from a lot of powerhouse station antennas, AM and FM. I was wondering about signal strength so I know how "strong" of an FM notch filter I need to build. I don't listen much these days below the AM BCB so all the massive images from the AM stations down there I can ignore for now.

[mark.]

I answered my own question. I dragged my heavy Cushman monitor to my computer area with the RSP1. It takes as little as 15-20dbm over the noise level to hear an image of a FM Broadcast band signal in the 200-350MHZ range of the unit. Located where I am, even with no antenna connected to the RSP1 I have some FM stations in the 5-10dbm above the noise level. With an outdoor antenna the entire band is heard multiple times above and below the original band. So if even fairly weak FM stations have images, I'll have to have a strong filter that cuts them down to barely discernible. UHG.