To answer the question yes you can install your outside antenna in the attic if needed.
Do you need to ground an antenna in the attic.
This isn t the ideal situation for installation of an outside antenna but sometimes it is necessary based on a number of factors.
Agreeing with adtech i don t see the nec requiring you to ground an indoor antenna system.
Antennas mine are receive only for fm tv and public safety bands will be generally restricted to the attic.
If you would like more information or need help installing your booster check out our support center.
If you have no access it s hard for me to tell you to go to extremes to find a way.