Aerial with Sky

I picked up an outside TV Aerial with an amplifier, In the interest of having an option of viewing other channels arond the house withouth having to get more decoders.

At the moment I have a magic eye in the main bedroom so I can watch sky upstairs.I know there is 12 volts on the coax to power the magic eye.
Will this have a negative effect on the amplifier of the Aerial.

I noticed there is a connection on the back of the current decoder for another Aerial, should I connec in there perhaps?

Anyone have something like this done? Aerial and sky dish on the roof?

I am outside cable area

A relation of mine has a normal rabbits ears to pick up the four Irish TV channels. In addition, he bought a secondhand Sky kit (dish, box etc.) and a UK Sky Card where he gets all the BBC's, ITV's, Ch4, Five, Sky News and several more free. Thus, the only thing he now pays for watching TV is his TV License!!!

Shouldn't be a problem, have seen a similar setup before.