If you have a Winegard Sensar antenna, the antenna "booster" is inside the antenna itself. However, not all models of the antenna have an amp in them.
The reason the amp is located in the antenna is to compensate for losses in the coax feed.
The antenna amp needs to be powered by 12VDC though. Typically, 12V is injected in the coax somewhere inside of the coach.
This means the coax is used for both the TV signal (going down the coax) and the 12V power for the amp (going up the coax). This alleviates the need for a second set of wires (and holes in the roof) to connect 12V to the antenna.
If your coach has a QUEST QS53D coax switch - that was installed by the factory - it will supply 12VDC itself, alleviating the need for an adapter that provides 12V.
On that switch, there is a power on/off switch. This power switch turns 12V on or off for the antenna amp only.
Here is a manual for the Winegard Sensar antenna showing the 12V connection methodology: http://www.winegard.com/kbase/upload/2452013.pdf
Note that if you have the Quest box, you do not need the little box shown in step 11.
Here is a manual for the Quest Coax Switch:
In the section: HOOKING UP THE ROOF ANTENNA TO THE QS53DVD UNIT in the manual, it tells you that you don't need the 12V box for the antenna when using the Quest Switch because the switch itself supplies 12V power to the amp (unless of course you turn the switch off).
I was having a lot of problems with my Winegard antenna. Sometimes it would work, and sometimes it would'nt. With the antenna amp exposed to the elements above the roof, I am thinking that nearby lightning or some other calamity may have damaged it.
Recently, I replaced the Winegard antenna with a JACK OA-8000, and everything works perfectly.
There are several different versions of the JACK antenna, but the OA-8000 is designed to directly replace the Winegard Sensar antenna without any modification to the mount.
In other words, the Jack OA-8000 is designed to use the Winegard roof mount, so you do not have to replace it. It also has an amp in the antenna, and uses the same 12V source.
So literally, it is a 5 minute swap out of antennas (removal and replacement of two e-clips and coax).