Our boat came with a built-in TV antenna, but we only this month discovered (after owning the boat almost a year!) that it has a little 12-V amplifier which must be turned on to enhance reception.
Perhaps we are the only ones not to notice - but it was never mentioned at PDQ U and, until recently, I'd never been able to find the amplifier. Turns out it's pretty well hidden - deep inside the wheelhouse way over on the starboard side. In case you've never seen it, here's a photo: (click to view): http://www.geocities.com/snodoglog/TVam ... 919-EM.jpg
In order to function, the 12 V breaker marked "TV" must be turned ON, but more importantly, a tiny switch on the unit itself must be turned to "DC".
Turning this baby on has done wonders for our TV reception!
Henry - Sno' Dog