So the splitter is actually splitting the signal three ways.
Depending on the type of booster used the three outlets may have equal gain or it may be that one outlet has half the gain and the other half is split between two outlets. In the latter case the outlet with the longest co-axial cable run will receive the least signal of all.
Look at the booster/splitter being used to see what gain is on each outlet.
Different models have different gain figures and the number of outlets on a booster can considerably reduce the signal supplied to each outlet.
I use a single ONE outlet booster where the aerial first enters the property from the roof and another four outlet booster with switched high gain to supply signals to TV. DVD Recorder, Humax PVR, separate freeview STB. The latter is this Maxview model :
http://www.maxview.co.uk/acatalog/di...mplifiers.html
http://www.maxview.co.uk/acatalog/TV...&_FILTERS.html