BFL13 wrote:
I have looked at wifi extenders (lots of those) but can't make out how they can pick the right wifi signal to extend by wireless and then relay that to the farther along device. Some(all?) have LAN from the extender back to the first wifi source box and then they wifi from there, (I think)
What you are describing sounds more like an Access Point, not a Wi Fi Extender. All the Wi Fi extenders I have used get plugged into the wall. Then there is either an App or a Web Interface that you connect to the Extender with. Then you tell the Extender what SSID you want to connect to. It connects to that SSID. Generally, you would give the Extender's SSID the same SSID you normally use, however, if you have older Wi Fi devices that don't auto select the strongest signal, you can name the Extender's SSID something different so you know you are on the strongest signal.
With that being said, there are Access Points that can act as Extenders/Repeaters that don't need to be wired. Just be careful as some may require being setup wired directly to the router, then used wireless.
-Michael