Hello  @greg-n-houston 

Thank you for the inquiry.In general, Range extender speed usually slower than Router's as receives data from the router wirelessly and then forward it to the Wi-Fi network clients and speed will decrease during the transmission.

First reason is that Range Extender works in ' half-duplex ' mode in extender mode,  it can only talk to the main router or the wireless client device in either way, not the same time, the link speed at physical layer will cut to half. On the other hand, the actual speed test could be around 40%-60% of wireless link speed due to overhead in the communication.  Here is an article explained the actual speed and link speed,  Why isn’t my Wi-Fi as fast as advertised?

Thus, in extender mode, we use range extender mainly to increase the Wi-Fi coverage in WiFi dead speed, not increase speed. 

We'd recommend using Range extender in  AP Mode and wire it to the router via Ethernet cable for higher speed. If the ISP bandwidth is over 100Mbps, you could a Range Extender with Gigabit port (RE315 is equipped with 100Mbps port)