I have a desktop which dual-boots to Kubuntu 14.04 by preference, or Windows 7. My wife has an iMac desktop and we have various Wi-Fi tablets and phones. We have a Technicolor tg582n router to which the desktops are connected by ethernet through TP-Link PA211 "Powerline" Home plugs; we use two TP-Link WPA271 Home plugs for Wi-Fi in the parts of the house not reached by the TG582n.
I recently reset the five TP-link devices because our broadband kept dropping out. They now have factory default settings except for a password for security on the Wi-Fi devices. We now have broadband on all devices (including my desktop on Windows) at about 16Mbps, the speed advertised by our ISP and ample for our use. There is one exception: whereas I had an excellent Ethernet connection on Kubuntu before, I now need to use a Wi-Fi dongle and it is noticeably slower. Any help much appreciated. To make this clear, I only need the dongle because Kubuntu won't now connect by Ethernet, as it did before I reset the home plugs. Before, my desktop connected by ethernet in Windows and Kubuntu; now only Windows connects by Ethernet.
The dongle is OK, the problem is that WiFi is always slower than Ethernet.
Edit: Now getting 14Mbps download but still stuck on @Fabby's stage 4. Output of ifconfig:
WGCman@WGCman-XXXX-D3:~$ sudo ethtool --change eth0 speed 100 duplex full autoneg off [sudo] password for WGCman: WGCman@WGCman-XXXX-D3:~$ ifconfig eth0 Link encap:Ethernet HWaddr fc:aa:14:06:xx:xx inet addr:192.168.1.70 Bcast:192.168.1.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:100 Metric:1 RX packets:88065 errors:0 dropped:0 overruns:0 frame:0 TX packets:46875 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:22091647 (22.0 MB) TX bytes:3947548 (3.9 MB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:1928 errors:0 dropped:0 overruns:0 frame:0 TX packets:1928 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:283489 (283.4 KB) TX bytes:283489 (283.4 KB)