On my 2001 35' Express the splitter in on the right side wall of my electrical panel - high by the 12 volt section. It does seem hidden but convientient once you know where it is. Over the years any issues I have had with TV reception is always the dock connection 90% of the time and the boat connection 10% of the time. The dock connectors take a beating in the winter in New England. And, the push pull connections are the worse option. If using them, buy good gold ones and plan on replacing them every year or two. RT
Before you blame the splitter, connect a VCR/DVD player to the cockpit connector using a short "F" connector / cable. That will isolate your problem to dock, cable or splitter. Capt. George
The splitter on my boat is in the compartment behind the TV's. You have to remove 4 screws to remove the panel to access it. The panel is just above the door that holds the fire extinguisher on the right just before entering the forward cabin. I had the same problem as you. It turns out the boat side cable connection (next to the shore power cord) was bad. Works great now.
The location depends if you are an A-Plan or B-Plan layout. B Layout is in the Forward part of the dinette seating storage area. If you reach in there and feel around, you should find it. A-Plan may be in the electrical panel or in the master stateroom behind the TV. I can't remember exactly. The switch will be black and hard to find in the cabinets. You are going to need a flashlight and patience I believe.
On my 3700 it was at the base of the electrical panel, inside the plexi cover. It switches between the antenna (buried behind the electrical panel) and the cockpit connection. Your antenna, if you have one installed, needs to be powered to work, there is a power supply behind the electrical panel or below it, behind the aft dinette seat back (where the battery charger is located) at least that's how my boat is arranged.