Constantly dropouts and hangers

OK, this keyboard / mouse set was inexpensive. Therefore, I have no desire to pack it to go to the post office and send it back.
We have intensively on 2 PCs and a notebook tried (Windows 7 and 8), in different rooms, unfortunately, always with the same fatal result: There are always dropouts or 'hanger'. Then you have to wait until the contact is restored, and write the writing again. Although the distance between keyboard / mouse receiver direct, unobstructed "line of sight" of only 1 bs has 1.5 meters. We have another, old no-name wireless set that was even cheaper, where these problems do not occur. Logitech, I would have expected more. We keep it mothballed in the basement, as emergency reserve set.