Why can one antenna escape the loop, but not two? It has to do with the way tachyon signals work. A faster-than-light transmission will be received before it was sent in some reference frames, but not in the reference frame of the sender. However, if the recipient responds with a faster-than-light signal, the sender will receive the reply before sending the initial signal. Thus, it takes two transmissions in order to send a signal back in time. By eliminating all but one of the antennas, there is no way to transmit a signal into the past to reset the loop.