Amateur radio can go the distance off-grid, particularly HF. However, you and the other person/s need to be licensed in order to use those bands. Why licensed? That gives you the opportunity to practice your skills and develop your gear before disaster happens. Also, even if HF can propagate through the ionosphere, it is still dependent on band conditions. Sometimes it’s good, sometimes it’s dead. It’s also one reason that having a lot of practice will play a big part in your success.

Otherwise, for 50 miles, a good fixed station with a directional antenna for BOTH stations and good line-of-sight (depends on terrain) is possible using VHF or UHF. Or, a repeater can also help you go the distance if you are using a portable (handheld) or mobile radio. These will of course require a power supply (can be off-grid solar + batteries), as well as a good antenna setup.