How old is the caravan Jamie & what model?
Does it have a TV socket inside the battery box and possibly a short length of coax with a male TV plug next to the status box which isn't plugged into anything?
If so, you need to plug the external aerial into the socket in the battery box, unplug the lead from the roof mounted aerial that goes into the status box, and plug the short length of cable into the status box where you just pulled the roof mounted lead out.
Hope that makes sense.
If your main TV point in the caravan has two aerial sockets, one like a traditional aerial socket, and another that has a screw type thread satellite conection, then the connection in the battery box is routed directly to the screw thread satellite connection on the panel near the TV. The traditional aerial socket is wired back to the status amplifier.
If you are experimenting by plugging the external aerial directly into the status box, then this should work so long as you have plugged the external aerial into the input side of the status box, replacing the feed from the roof top aerial.
It should still power up. If it doesn't you may have a short on the external aerial. Check the wiring in the plug and where the cable is fastened to the aerial. Perhaps one of the fine shielding wires is touching the central core wire.