Now that we have a better idea of what you want, here are some observations.
The type of wireless connection we often use with portable computers is called a WiFi connection. It sometimes is also called the 802.11 standard. These are references to a published standard that uses short range microwaves for a two-way communication using digital technology. These devices use a have a range of up to about 100 m or about 300 feet or so. Provided there are no obstacles like large metal sheets. The outside skin of your travel trailer makes it very hard for microwaves to penetrate, unless there is an opening. If you take the screens off of your Windows, then there is an opening for the microwaves to get in. But the antenna must be fairly close to the window in order to capture signals that are coming in at an angle. You're a have had similar experience with the cell phone systems.
Now there is an important difference between the cell phone system and the WiFi system. Cell phones are meant to have a range of a few miles by using the help of high power relays on top of high towers with large antennas. That is an important difference.
The point being made here is this, with suitable outdoor antennas on both ends you can expect to have reliable communications up to 300 feet or so. Both the router and the client will have to have antennas that are not obstructed by large metallic objects. Also can create walls, heavy foliage and even wooden structures can weaken the range of these type of devices because they run at a very low power level.
Easy you can place the antenna near a window with no screen, or you can mount a short antenna on top of the roof or even on the side of the travel trailer. Also,microwaves can not go around metal objects that are more than about two feet in diameter.
The basic antennae used for these devices looks like what we call a rubber ducky. However, the rubber ducky has to be specific for the application you're using. It has to be for the 802.11g standard. Which specifies two frequency bands in the microwave region.
Just to give you an orientation of what sort of antenna are used for these devices, here is a link to a place where people love to tear them up and make them work better. Of course, you'll have to do that. But it's fun to see some of the tricks that people have done with these little antennas by tearing them up and rearranging them make similar but more powerful. But In your case you don't really need to do that. Just get the antenna close to a window, or mount outside of the window on a bracket.
http://www.instructables.com/id/WIFI-Antenna-Hack!/Watch the video. Very entertaining!
And by the way, I used to be an active radio amateur years ago and it was fun playing around with antennas and things like that.
