[Grumps]

Thanks for responding Rob. It's helpful to know that the problem is not the cable mix. So it's back to checking the junctions. There's just the additional junction consisting of two F connectors and the coupler. Surely that would not create much resistance of pass the signal just one way. So by elimination it may be just the way I've fitted the connectors. I'll check this yet again tomorrow morning and let you know how I get on.