If you want to extend a 5 GHz network with a range extender, you will need to use a model that supports the 5 GHz frequency, like the Sitecom WLX-5000 Wi-Fi Range Extender Dual-Band N600, or WLX-5100 Wi-Fi Wall Mount Range Extender Dualband AC750. Click here for more information about the WLX-5000 or here for more information about the WLX-5100. 

With a dual-band range extender you simultaneously increase the range of your 2.4 GHz and 5 GHz wireless networks.