> Maybe Enoch and Bette can double the transmission power
> by a parallel link ??
My impression from facts gleaned and speculation presented is that the walls themselves act as a barrier to the transmissions. If you remember, the probes are using a VLF (very low frequency) transmission to permit distant transmission through obstacles. But it was not working while Enoch and Bette were inside. Had it been, we would have been able to hear Bette while Enoch's systems were being repaired.
Also, we have been told that each probe transmits on a slightly different frequency. It is perhaps likely that they use the "correct" frequency when acting as a relay, but it is not at all clear that they can choose to use the frequency of another probe at will. If they cannot, then two transmitting together would be sending two disparate signals and not doubling the output as you suggest.