So I've recently moved and am just now getting around to thinking about having my Directv moved. They want a few hundred to come and do the install which I'd like to avoid paying since it's not that hard to do. There's literally 20 years worth of dishes up on the roof (There's at least one RCA one still up there) so I wanna reuse one of those. There's a World Direct dish up there with an 8 way splitter attached to it that looks promising. I figure with the way people move in NYC at least one of those spaces on the splitter is now vacant. My question is how to test which spot is empty. My idea is getting a multimeter and testing each cable for voltage, with a dead one being an open/unused space. Is this a good idea or is there a right/better way to do this? Thanks!