A long long time ago when we had Sky we ran a picture to a upstairs bedroom via a coax cable. We could only change the channel from the main box.
If I remember correctly this is how the connections were made. Sky cable into Sky box, scart from Sky box to main TV and coax from the RF out socket on the Sky box to the other TV. We then picked the picture up on the upstairs TV on a spare analogue channel.
Don't know if this will be any help to you but it may point you in the right direction.