The "proper way" uses the Sky Digibox RF modulator (or IO-Link) to combine the Freeview and Digibox UHF signals. These devices are specifically designed for this job and should minimise harmonic interference as well as amplifying a little - unlike a splitter, which is designed to split a signal to feed two or more devices with consequent reduction in signal strength.
I am still struggling with this. When using the new Wolsey 334024 amp which supports the Sky IR Pass, the Sky RF2 picture on all the TVs is snowy and not good. However the magic eyes now work and I can change channels on the Sky STB from the TVs upstairs.
When using my old Wolsey 334038 amp the Sky RF2 picture was much better and clearer but as it didn't support Sky IR Pass I was unable to change the channels etc.
(Proper-ish way) I've tried connecting the cable from the aerial on the roof to the down cable that goes to the TV/Radio wall socket in the living room by joining them with a barrel in the loft.
Then from the TV port on the wall socket in the living room, I connected this to RF IN on the IO LINK. And then connected another cable from the RF OUT on the IO LINK to the Sky return feed cable that goes back up to the loft, the other end of this cable was then connected in to the UHF in on the Wolsey 334024 amp.
When I do this I get the snowy Sky RF2 picture on all the TVs on the analogue channel. However I then lose Digital Freeview altogether and it says No Signal on the TVs.
(Bodge way) If I try to wire it up the other way using the splitter in the loft instead, where the cable from the aerial and the cable from the Sky return feed (RF OUT) both connect to the UHF port on the amp. I also get a poor snowy picture for the Sky on all the TV's, but Freeview works OK in this case.
I can't understand why the older Wolsey amp gives a better picture for the Sky RF2 signal. Or why I lose Freeview TV signal when using the RF IN port on the IO LINK.
Another thing I notice is when using the old 334038 amp if I plug in the cable to the UHF port the blue light on the amp lights up even though I haven't plugged the amp in to the mains electric yet. I assume this means it can get power from the RF OUT port on the IO LINK / Sky STB.
If I plug in the new 334024 amp and connect the UHF cable it does not light up and power on, it only powers on when I actually plug it in to the mains electric.