Well here is the manual for the 3100.
You are unlikely to be getting DVD content over antenna wires. If you will note that on page 11 there is a wiring diagram from the back of the radio that shows AV output1 and 2 consisting of
1. A standard set of AV composite cables (yellow red white) which would be run directly to the VIDEO (not antenna) input of probably the closest TV. Experience is that lots of times the factory gets this plug in process wrong so you should check your connections to insure they are color matched at both ends. (OUTPUT from DVD player to INPUT on the TV.)
2. There is in the same diagram an option to send output though a SPECIAL AV composite wire that ENDS at the 2nd TV inpur jacks just like the first cable...but starts with what resembles a headphone jack but is actually a 3way composite AV jack. This option may or may not have been installed in your camper...but can be added with the purchase of a cable at the local Amazon! https://www.amazon.com/Cable-Showcas...nd+video+cable
Alternatively...if you find you want DVD somewhere it isn't wired in...you can buy a portable player for $29 bucks or so and plug it in wherever you want. A blue ray player would provide way better quality than you will get from the Furrion on any TV and allow you to use HDMI high definition sources.
Hope this helps a bit.
EDIT....yes...the antenna has a power boost that needs to be turned off if you are watching cable to prevent static and interference.