Hi

When I connect the computer to the tv I hear a humming sound and small waves appear on the tv

when I disconnect the tv from the antenna the humming and the waves disappear

does anyone have any idea what I should do to fix the problem without having to disconnect the cable all of the time

Well, it apears the antenna is causing some electrical disturbance, hance i suggest you try to use alominium foil to cover your other cables (AKA shielding) . If the disturbance appears it means that something in the TV is abbreviating..