SOHO Surf Speed loss connecting to public wifi

Am using a Surf SOHO to connect to a public WiFi and retransmit my own SSID to add a wee bit of security. But running Speedtest when connected to my SSID gives very significant speed degradation compared to being directly connected to the public WiFi. There is nothing sophisticated in my setup of the SOHO and I don’t see anything that would cause the speed to slow down so much but speedtest confirms the speed loss and the user experience browsing the internet when connected to my own SSID does too, its slow. Any suggestions would be appreciated.