The set up is as follows:
I've got a TV with a duel channel recorder box separate to it. The coax cable comes down from the aerial /signal amplifier and into the 'RF in' plug on the recorder box. Another coax cable goes from the 'RF out' plug on the recorder to the tv.

Here's the problem:
In this configuration (how it used to be before we got a new TV) the Signal is stuttery with a broken picture and broken audio when viewing from both the TV itself and through the recorder box. The picture I have posted is of this.

When I connect the aerial cable with the coax going to the TV together so the signal is going straight to the TV, bypassing the recorder, the picture and audio is perfect.
I get the same perfect image and audio when I switch the "polarity" of the coax cables going into the recorder box but no signal at all when trying to view channels through the recorder.

Could this be a problem with the recorder box or am I missing something entirely?

Cheers, Sam