I tried flashing dietpi to a microsd card and setting the wifi info in the dietpi.txt file. It would not connect. Then I tried setting up the wifi through the pi itself. I scanned for the wifi networks and I could see my 2.4 Ghz ssid, but not the 5 Ghz. Is there some other setting I have to change for it to see 5 Ghz networks?
I just got a B+ the other day. I didn’t have to do anything special to get WiFi working. I scanned for networks and it picked up my 5 GHz AP. Performance is very good actually, about 90 Mb/s send and 94 Mb/s receive, so similar to the Ethernet port on the old Pi 3.
Make sure the region is set up correctly on the AP and Pi, as some channels are not available in some regions, or have limitations like requiring DFS/TPC.
That was it. Once I set it to the US and scanned the networks again, the 5 GHz network showed up.
Thanks!
Hello I installed and configed the wifi country and I see 5ghz networks before installing AP but I only see 2.4ghz as AP. On startup it says wifi country not set i checked the wpa_supplicant file and the wifi country is set so could anyone who says the just configed and everything works maby explain what they did plz. 
Thank you