What is subspace radio?
A means of sending a signal through subspace, so that it is not limited by the speed of light. This is done by creating a subspace distortion which propagates in much the same way as an electromagnetic field. A large amount of energy is needed to send a signal any large distance, and the more energy that is available, the deeper the signal can be forced into subspace. However, the signal dissipates over time, eventually releasing the energy that is left as an electromagnetic field. A more powerful initial signal can travel farther before this happens, but there is a limit; too much energy and the level of subspace that is used won’t be tightly coupled to our own space-time any more, and the signal will probably go awry. The Federation (and presumably other Alpha and Beta Quadrant groups) use subspace relay networks to periodically boost subspace signal strengths. We see one of these in “Aquiel” [TNG] and Seven of Nine uses one to “phone home” in “Hunters” [VOY]. ….
