"diluted" - ?? True white noise (within a specified bandwidth) has a constant energy for all frequencies. Without getting into fractions, one way to generate 1 MHz white noise would be to get one million little sine wave generators, tune each one to a different frequency between 1 Hz and 1,000,000 Hz, and add all of the outputs together. Yes, there are lots of other ways to do this, but this is just to explain the concept. None of the individual generators have any harmonics in their outputs, so there is no constrtructive/destructive interference.
Not only do I not see any "diluting", I wrote about this a few years ago as a true ultimate zapper.