If a charge is moving at constant velocity for inertial frame
, it is always possible to make a change of coordinates, applying Lorentz transformation, to the inertial frame of the particle, say
, the field is static all over the space. And frame
is moving around this static field. So, there is no signal or information to be transmitted.
Of course we can think that the charge was not always there. At some moment a device separated positive and negative charges, and surely some acceleration was involved. EM waves were emitted then, sending the information through the space.