I may have misled you on my statement of the ANTENNA PANEL WAL PLATE working just fine using a JACK INJECTOR between the F CONNECTOR and your TV SET. The ANTENNA PANEL WALL PLATE will have a DC BLOCK feeding the F-connector on the face plate.
You will need to tap into the RG CABLE going up to the JACK ANTENNA. Here is a diagram on how the ANTENNA PANEL WALL PLATE is hooked up..
The MIDDLE CONNECTOR comes from the CABLE OUTSIDE connection.
Also in this photo you can see the +12VDC cable hooked up. NOTE the push on spade lug connector... This is what you need to test for 12VDC. Apparently you are missing this for some reason. This DC VOLTAGE comes from your on-board converter unit when plugged into shore power and also comes from you charged up installed 12VDC trailer BATTERY. There may be a FUSE on the board itself or possible in the 12VDC Distribution PANEL where all of the 12VDC fuses are located.
The easiest thing for me was to just remove the BATWING antenna and MOUNT THE JACK ANETNNA on the roof. It uses the same BOLT PATTERN and all you do is just connect up the existing RG CABLE. Apparently you are missing the 12VDC that gets sent up to the roof from the ANTENNA PANEL WALL PLATE. ALSO NOTE in this photo you can see the RED LED light I was referring to earlier on the bottom of the JACK ANTENNA. This will light up when 12VDC is being applied from the ANTENNA PANEL WALL PLATE or your JACK DC INJECTION unit.
The WALL PLATE has a small PUSH BUTTON and when pushed it will turn on a small LED light on the WALL PLATE telling you the 12VDC is present and being applied. If you don't see the LED 'ON' then you do not have 12VDC being applied.
This would be you best bet getting the ANTENNA WALL PLATE to work as this will feed both your living room HDTV and your BEDROOM HDTV when in ANTENNA MODE picking up digital signals from the trailer roof top OTA antenna.
The cigarette plug socket is a great place to plug-in your cell phone 12VDC charger cable... Use mine all the time...