we used to have one of the moonraker black box aerials which used to sit about an inch above the cratch in normal use, we did used to have a pole it could be switched to for some extra height (clothesline prop was ideal), Generally it worked well apart from in poor signal areas. A friend had a log periodic on their boat and one evening we tried switching aerials, where his tv could find 4 channels using his log periodic it found 12 with the moonraker in the same spot, where ours found 2 channels with the moonraker (rubbish tuner in the tv) it found nothing with the log periodic.