107.5 is one of several signals that transmit from Mount Potosi. (88.9, 89.7, 93.1, 97.1 and 104.3 are the others.)
At more than 8000 feet above sea level, Potosi has phenomenal line-of-sight coverage that allows the signals up there to be heard at huge distances from Las Vegas. You can carry the Potosi FMs in the car down I-15 most of the way to Baker, and up I-15 into Arizona. But Potosi is also much more distant from Vegas than Black Mountain above Henderson, where the rest of the full-market FMs (88.1, 90.5, 91.5, 92.3, 94.1, 95.5, 96.3, 98.5, 100.5, 101.9, 102.7, 103.5, 106.5) are located. The Black Mountain FMs lack the enormous coverage area of the Potosi FMs, but they have more raw power and are much closer to the Strip, and so they come in significantly better there than the Potosi signals do.
In addition, the tall buildings on the Strip cause an enormous amount of multipath reflection on all FM signals, but more so on the Potosi FMs than the Black Mountain signals. The Strip was notorious as one of the worst FM spots in the country even before the high-powered boosters (105.7, etc.) started to sign on from the Stratosphere. Those just made a bad situation worse.