Connected to my tv (HDMI), will be problem with wifi.., why?

Helo all !

I have a Dell 7537 notebbok.

Produces the following problems:

When I connect it to my tv (with HDMI cable), the wifi will be very very poor. (about: 0,23 mb/s)

-But if I stop the connection, between the TV and the notebook, the speed is all ok.

Why does this happen?

-All the latest drivers installed
-My tv: is a Panasonic 42PV80pa

Regards: Laci