Question 6A402

Link coupling is a method used to transfer RF energy between two resonant circuits, such as those in separate amplifier stages. It achieves this by using a short, low-impedance transmission line (the "link") to connect small coupling coils, typically one or two turns, inductively coupled to the main coils of each resonant circuit. Option A correctly describes this. The low-impedance nature of the link (often coaxial cable) allows for efficient power transfer over distances that might be "relatively large" compared to direct inductive or capacitive coupling, providing flexibility in component placement and mechanical layout. Option B is partially true in that link coupling can be used for short distances, but it doesn't highlight the primary advantage of separating stages or the mechanism. Option C describes a different type of device (a closed-loop coupler or directional coupler), which is not the standard method of link coupling between amplifier stages. Therefore, D is also incorrect.