We looked into getting a Netgear WIFI extender for the house. We went to Best Buy and talked to the folks there. The guy who helped us explained, that even though the range of WIFI is extended, the upload and download speed was considerably reduced ... like 50%. Thats no problem if you are using static web pages, but for streaming video or gaming, it could cause too much of a slow down.
We didn't want that, only to find out once we returned home (with new laptop's), that our Netgear wifi router was Dual Band. When we connected to the 5G band on all our devices, everything started running, like .... WOW!
Glad we talked to the guy first, and he had us take a second look at our current router. He's the one that explained to us how the dual band router works.
Turns out, our new television in the camper now pick up our WIFI great at home, as does our computers and every thing else, even in the camper, parked in the drive way.
Now... if the OP is looked for a way to extend campground WIFI, or a WIFI that he does not own, that's a different matter.
If you are able to tap into a campground WIFI and extend the range, then you better believe everyone else around you will be using the same signal from your extender too, slowing it down even more, as campground wifi's have the known reputation of running horrible when so many attempt to connect all at the same time.
