Wires.

Connect the USB cable to the computer and the DEC2000, the antenna cable to the antenna and the DEC2000, the old antenna cable to the DEC2000 and the TV, the SCART cable to the DEC2000 and the TV and the power cable to a 220/230/240V outlet, preferably one with a manual power switch.

Don't worry about the plethora of cables hanging all over the place now: the antenna ruined the picture anyway. Plus, have you noticed how ugly a TV set actually is?