Originally Posted by
Hot 'n' High
Certainly older equipment I looked after suffered from "garbling" when transponders/IFFs were in close proximity to one another and this
IEEE paper seems to cover that aspect in ADS-B too. Thus it was (and probably still is) as per the post from
sycamore to prevent such issues.
Garbling is when two messages are transmitted too closely in time, not due to spatial proximity. The density in that paper refers to the number of aircraft that can be heard, not the number of planes per cubic meter. This is similar to two people in the same room talking at the same time to a third person.
The mention of TCAS makes the most sense.