Below is a diagram of my setup. When I plug into the actiontec box upstairs directly I get fast internet (70Mbps)
when I plug into/log on to the airport express upstairs i can only get around 20 Mbps. What am I doing wrong?
Did you test with a laptop, directly connected to the Ethernet connection upstairs, with a laptop, to see if you get the same speed? Also, these Actiontec devices are supposed to support firmware upgrades. You should contact Actiontec to see if they have a newer firmware version for your MoCA devices..
It appears based on your speed report that the upstairs Airport Express is connecting to the downstairs Airport Express using WiFi which is the way that an extender works.
What you need to do is set the upstairs Airport Express as an AP.
In this site there is a very complete explanation of how to do this. Quite simple and once it is setup you will get the same 70 Mbps you are getting when conected to the Actiontec.