Hello, and welcome. My name is Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority. Let’s get started!
Hi there, sorry to hear you're having trouble,
when you say a digital box, do you mean a tuner box, being used with an aerial?
If so, have you considered just getting a separate antenna and/or tuner box for the bedroom tv? This would be a more direct approach and much less prone to interference.
Other than that, have you tried a long coax cable, which is usually less susceptible to interference than the scart cable or the wireless sender would be. You could use scart to the main tv though, if you need to free up the coaxial port to run upstairs.