I just posted this in another thread a couple of days ago, but.....
The Winegard panel that contains the booster amplifier almost always has at least one F type male tv connector and a 12vdc cigarette lighter type power connecter. There will be a small switch and an LED indicator light. The switch might be a little slide switch or it might be a push on/push off type. The LED might be red or it might be green. It will look very similar to this one:
The amp must be ON to use antenna reception. It must be OFF for satellite or cable tv use.
Sometimes they're in the entertainment center somewhere. Folks have also reported them in closets. My TV is on a swing arm in front of an open compartment that is deep enough for an older style tube tv. The antenna connectors and 110vac outlets are in the compartment, but hidden from view by a half panel.
Sometimes they are located in the bedroom; ours is on the wall where the tv is obviously supposed to be, but it is not too obvious because it is behind a trim panel that part blocks your view of it.
If it is not obviously visible, you've got to be a touch aggressive in searching for it.
And, as several others have pointed out, it doesn't seem that Keystone can be relied upon to properly tighten all the connectors in the television/cable/satellite cabling which can seriously impact the quality of reception. So, there are two options. If the trailer is still in warranty, you could take it back to your dealer and insist that a tech go through it stem to stern and pull every panel off the wall and tighten every connector.
Or......
Get out your #2 square driver and 7/16" open end wrench. Systematically remove each panel from the wall and tighten each connection. Generally, tv connectors should be tightened using the wrench just tight enough that they can no longer be undone by hand. So hand tighten and then use the wrench to add a quarter turn or so and no more. Every single connection has to be checked including the sat prep ones (f you plan to use them, that is.)
I did go up on the roof to slide back the rubber boot on the antenna connection and check it for tightness. I did not disturb the dicor caulk to check the other side of the roof pass through. If I think there is a problem there, I will, but it's the one connector I'll let slide until a problem arises.
Reward yourself with a beverage of choice for a job well done.