no matter what you install in your camper, and no mater how much power your device has, the place you are stealing the WIFI FROM still needs to be able to talk back TO your device.
The campground (or other) device only has limited power.
If you have a High Power access point, you can send your signal a long distance, but the device you are talking to still needs to be able to talk back to you.
This weak transmitter on far end problem can only be solved 2 ways.
Very sensitive receiver: this is an expensive option, but you need to remember there is much competition for the same frequency band that is shared by all devices, so even a sensitive receiver has limited practicality because of the clutter of noise from all the other devices you can't connect to because they are running encryption.
Directional antenna: This is the best solution. this can be a Yagi or a flat panel directional antenna. This works because you can point at what you want to hear, but hopefully block out what you don't want to hear.
Repeaters: These can be a PITA. you need to figure this device is doing 2 things. A its acting as a client connecting to the campground system. B its also acting as a Access Point so your PC or phone (the clients) can talk TO the device. so every now the device has to do everything 2X, which cuts your speed in half.
Also every one I have seen, if your talking to an open WIFI system, your end will also be open, thus any of your neighbors will connect to it as well. You can name it "hacker" or something like that, but most users have there phone set to connect to "any open wifi" so the phone owner don't even see the name of your SSID.
2 unit repeater:
1 Access Point is talking to the remote device and its hard wired to another access point which is your local broadcast domain. you can use a password on your local AP to keep your neighbors off. But its too hard to setup.
Also remember most campgrounds might have 10mbps internet, and they share this across 100's of campers that each has 3 or 4 devices, and everyone thinks they will stream TV or watch youtube on the phone, by the time your done the service is really bad.
I decided its not worth it and just started using 4G hotspot. Because of what I do for a living, I carry both Verizon and ATT hot spots. On the East coast of USA I can't think of the last place I was that I did not have access.