Sections §73.807 and §73.825 of the FCC Rules outline the minimum distance separation requirements between LPFM stations and other broadcast facilities.
However, it's important to understand that the "vacant channels" search feature on Radio Locator is designed for individuals interested in using small consumer-grade FM transmitting devices, such as those that connect to a car's lighter port to broadcast audio from a cell phone. These devices operate under Part 15 of the FCC Rules. The Radio Locator "vacant channels" search does not consider any of the FCC Rules specific to LPFM.
Therefore, it is strongly advised not to rely on Radio Locator to determine potential available channels for LPFM applications.