This is not true. For frequency hoppers (FHSS), as more users come on, you start to loose data in a statistically deterministic way. You can model this loss and account for it with redundant data. This loss does not affect the range at all, just the amount of data that gets through (per unit of time)

And with new FCC rules, you can intelligently avoid frequency bins that are showing signs of interference, so you just hop around them. It used to be that you had to hop on all 75 bins equally. This is a big improvement in the regulations.


Direct Sequence (DSSS) is totally different.

EDIT Actually, more users in theory does indeed reduce the range even for a frequency hopping system. After the maximum range is reached (you have begun to use up all of the redundant data) then more users will cause more data to be lost. But I do not think this happens by some inverse square law like 4 users yields 2x reduction