It is well known that phase velocities can be FTL (faster than light). It is often said that group velocities cannot be FTL. But I doubt this last one. Starting from the Lienart-Wiechert delayed potential, what can be said for sure? For sure a response to a step signal cannot be FTL. But what about group velocity? And what about "signals" generally speaking? From classical (relativistic) physics, what can be precisely said about "signals" speed limitations? And what is usually meant by a "signal"? If, as I guess, group velocities can be FTL, I would appreciate some examples. If, in some circumstances, group velocities cannot be FTL, I like to know more about the conditions. I would like to become more precise about all these things. Thanks for your suggestions.