You didn't give a lot of info... year, model, etc, so I can only tell you that I had the same thing happen a couple of weeks ago. I bought my 98 Dolphin used. It did not come with the coach manual.
After much searching online I finally was able to determine the fuse was on the 12V panel located in one of the outside compartments. There are many fuses on this panel, too many to pull and check. Easier just to use a Volt Meter to check both sides of each fuse for 12V. The one with voltage only on one leg, not the other, is open.
Since the Antenna Booster was probably a factory install, it's not likely to have an in-line fuse.
Mike