Re-opening this......can anyone explain how you use these, please?
The one I have is operated thus.
Freeview (terrestrial directional aerial); unplug the aerial lead where it plugs into the booster (or tv if you don't have a booster) and plug into the finder. As you rotate the aerial the lights and sound will indicate max signal. Disconnect and plug lead back into booster/tv. Foolproof but watchout for villages in valleys where there may be a local transmission polarised by 90 degrees and you have to wind the aerial onto its side.
Sat; plug it inline using a short flylead. You need to have a pretty good idea of where to start pointing.