Problems with my new digibox? can anyone clever help me plz?

Ive bought a technika digibox from tesco and have set it up in my bedroom, the problem is its only picking up certain channels, when i have excellent signal and know that all channels can be recieved where i live. downstairs i have sky tv and have an aerial link from downstairs to my bedroom so i can watch whatever sky channel the tv downstairs is on. i have connected this aerial to the new digibox in my bedroom- is this the problem or is this ok? if this is the problem then how do i get around it as this is the only aerial i have im my bedroom? also if someone knows anything else it could be, any help would be great, thank you much x
Answer
Its your aerial that is the problem i would buy a powered set top aerial from somewhere like argos or currys and use that to set up your digibox as the aerial link from down stairs if not put through a signal booster is not giving you a strong enough signal to get all the possible channels from the digibox i hope this helps