inductive coupling


I notice that both my digital SANGEAN PR-D5 and my analog SONY ICF-S5W and EX5 all can be tuned to a given frequency, and then used to boost a signal significantly on an ultralight tuned to the same frequency. My question is, why do the analogs work as a booster even when off while the digital works as a booster only when turned on?

Join to automatically receive all group messages.