Hi, I think I found the issue. The bottleneck looks to be the difference between WAN router connection, 1Gb lan port and 500Mb Internet Speed and the LAN connection to 841N that is 100Mb and also to WDR3600 that is connected to a 100Mb passive Switch.
If I connect the WDR3600 that have 1Gb port to the Archer C7 1Gb port directly I get for instance 240Mb on WIFI. I have to test by cable.
Also, this is a little more strange but I bought a 1Gb passive switch and connected it between the TP-LINK 841N and Archer C7 and now the upload and download are the same. 95Mb by cable and 55Mb by WIFI.
Could be some buffering issue on Archer C7, that have only 1 CPU and cannot sustain the speed correctly? The upload you go from a slow speed to faster, but on download you came from a faster to slower.
With my best regards
CGR