What do I need to setup a dual-band wifi range extender?

Factual Questions
1

Before anyone starts about the disadvantages of using a range extender I already know. I tried powerline adapters and they were a complete bust. My only option to get WiFi/network access to my living room is via a range extender. My WiFi signal in that room is pretty weak so need to boost it.

I have an AirPort Extreme Base Station that is a couple years old which broadcasts my WiFi signal.

As I understand it range extenders halve your throughput on the WiFi signal. To avoid this you can use a dual-band extender. Essentially it will talk with the base station on a 5Ghz channel and talk to your devices on a 2.4Ghz channel thus keeping throughput at full throttle.

Question is what devices will do that? I see Airport Express devices support both channels but cannot find a way to configure them to do this. Other devices suggest they do but again finding little in the way of how to configure it.

I would prefer an Airport Express as a range extender if possible but I’ll go with whatever works.

Any help appreciated!

2

I know nothing about range extenders, but have you tried moving your Base Station around, to see if you can get better reception with it in a different place? Lot’s of things in walls, like wires, pipes, heating ducts, can partially block WiFi signals. You might not think of a mirror as a problem, but it’s a big impenetrable sheet of metal as far as WiFi is concerned. We have a mirror in the half-bath between our wireless router and family room, which casts a “shadow”, making reception spotty if the router is in the wrong place.