Erika,
By "mifi ranger", I believe you mean "WiFi Ranger"?
Here's my take on the WiFi Ranger as it relates to use with Campground WiFi systems:
- By being roof-mounted, it increases my ability to pull in a more usable campground WiFi signal, especially for mobile devices (smart phones/tablets) whose built-in WiFi antennas may not be very effective in reliably picking up the campground WiFi signal
- By connecting my devices to the WiFi Ranger, I have a more secure network that I'm using versus having my devices connected directly to the campground WiFi system
- As you eluded to, as more users connect to the campground WiFi system and begin to use the available Internet, everyone gets less bandwidth and Internet gets slower for all. The WiFi Ranger does little to improve this, though you may be connected to the campground WiFi network with a stronger signal due to your antenna being roof mounted and that likely gives you some advantage
A question not asked is "Does my external Cellular Antenna really help me in some way?" The answer is yes. The MiFi, like a cell phone, has a built-in antenna. When I get in areas where the nearest cell site is distant, the available amount of signal to pickup is low. The goal here is to pickup as much of that weaker signal as possible. An external antenna is a big help here. One day, when I know I'm in an area where my cellular signal is lower, I will do some RSSI comparisons with and without the external Cellular Antenna.
For clarity, when I speak above about an external Cellular Antenna, this is used solely for the MiFi (or similar) Cellular Modem. I am not using an external antenna for my cellular phone. If I needed better cellular voice communications, I would consider an external cellular antenna / amplifier / cellular hotspot solution. Expensive - but if you need it.....