That is an over the air HD antennae on your roof. It picks up local stations broadcasting in HD. The button just above the broom closet (near the door) is an amplifier for HD signals. It will strengthen weak signals. Don't use it unless you need it because it adds static otherwise. Make sure it's off if you connect to an external feed (Cable, Satellite).
I use a Winegard Pathway X2 (Winegard Pathway X2 for DISH - DISH HD Portable Satellite TV Antenna
) for tailgating, etc. Service from Dish Network with month-month payments--no contracts, auto location of satellite, supports 2 receivers and gets its power from the coax so no extra power cords.
We hooked a splitter up to the Coax jack in the back storage compartment. Mostly works great. There are some wiring limitations so I had to make tradeoffs when using satellite. No HD outside, but using the wide screen gets me what I need. Also, I tune to channel 3 which gives me access to Dish programming. After 1 or 2 trips, I have the process down. With month-month service, we turn it off when not using for extended times. Sometimes requires a call to service to refresh the box, but works every time.
It's a cost effective way to get the college football games when we tailgate. I was one of the few RVs with the Longhorn Network last weekend, so we had a good crowd around the FR3 for it's maiden tailgating adventure.