Wiring down 4 floors for digital TV, amp but bad digital

[JNAScarb]

Hi

I'm a 20 minute walk from the TV transmitter, have an aerial in the loft through a Philex SLX1 aerial amp to a tv on the second floor, then I've wired coax through the house to the ground floor where I've got a TV with a digibox.

The analogue picture is great, but the digibox picture is either pixellated, jittery or anyway mostly green (that one's curious). The digibox works fine on the top floor.

I'm thinking it's a problem with signal strength despite the amp being set to max.

So .. what do I try next? How do I diagnose the problem?

(and that's before I interject another TV on the middle floor).

Cheers
J

[stoneyboy]

JNAScarb,
Try bypassing the amp so you feed directly from the aerial to the ground floor.
end

[plumbbob]

It's as Stoneyboy says, the problem is the opposite of what you think. The signal is so strong it is overloading the receiver.

Try fitting an attenuator in the line to reduce the gain to a manageable level.

[dazzlingdave76]

Have you done a volt drop test ?