Joshua Tree Nat'l Park question

I just came back from a week at JTNP and, as usual, monitor the 171.675 freq for the Nat'l Park service.

I am able to hear 171.675 from just about anywhere in the park with varying levels of quality (at it's worst, it's still quite usable).



I switched to the repeater input (172.675 per the DB) and WOW!. Although it's listed as a "repeater input" in the DB, it sounds like the output of a repeater. Over in the Jumbo Rocks area, it has a full quieting signal. Same 146.2 PL.



Another thing I noticed listening to this is some of the units will have a short beep at the end of their transmission on 172.675. I don't think I've ever heard this on 171.675.



So it sounds like 171.675 and 172.675 are a simulcast of sorts.



Is there a link frequency I am missing or perhaps someone can explain how this works ?



Thanks.

Joshua Tree Nat'l Park question