The Aerial Amplifier worked "out of the box"; I installed it in our attic near to the FM aerial (which is outside) and it immediately doubled the signal strength meaning my tuner can now pull stereo on all stations - including Smooth FM (two bars before - now 5 bars!). As a bonus, I've got my workshop radio also wired in to the other socket, so I get noise-free stereo in my attic as well! Most excellent product, thoroughly recommend it.