Thanks for that - we have a "complicated" setup! Aerial to VHS to DVD to STB to distribution amp to TV1 and TV2. All works fine until the NTL contractor changes the STB which they have now done twice in a week. The two sets lose the RF channels 1 2 3 & 4 and will only work if the VHS is switched on - then - if you change the cable channel the RF feed to TV2 is lost. All a bit strange. I just wondered if the new boxes from Samsung might have done something strange with the RF in/out. I will look at channel 65! Channel 51 is BBC1 here. Thanks again for the info.
Regards