If I am on-call 24/7, and required to respond to a call within 15 minutes, should I be compensated for the on-call time?
Question Details: In a location where I can not go anywhere or do anything that is outside of VHF radio range, or anything activity that would impede my ability to respond within 15 minutes?
If the location where you are "confined" to your 15-minute travel radius is your home and its immediate environs, then you are most likely not entitled to compensation save when actually called in. While you would not be free to travel however you like, you are in a position where you can do most things of your ordinary life--chores, sleeping, being with family, etc. etc. without interruption, in/around your own home. In that case, your on-call time is most likely not work time.
If on the other hand you are stationed out of some barracks, ready room, or the like, then if you are confined to that non-home vicinity, it may well be work time to be on call, since it is significantly restricting your non-work life for your employer's benefit and its behest. If this is the case, you should consult with an employment law attorney to evaluate the situation in greater details.