Oh wow, you're right -- I must have crossed that up in my head when taking it to the breadboard. Though, I've experimented with different values, and gotten pretty close to that (I don't have a 12uH inductor, but got close!). With lots of permutations, I can't get it consistently below about -60dBV with a single filter on the input like that. I am confident with more parts I can get it down -- I set up a 5th order filter at one point (cutting some traces and flying inductors FTW!), and saw it drop down to something like -90dBV. But at that part count, it's going to take a lot of real estate, and I think I'd rather find a part that just might be a better choice .