That may be the case or the source of the signal needs to be closer to the target or more powerful. If the signal was intended to mimick the defensive blast sent by the probes against Daniel then it is good that Zachary was not able to follow. The ET in the Big Tram may have been fooled into believing its "noise weapon" worked. That will reduce its effectiveness upon the probes and give them the chance to "play possum" while learning about the ETs in secret.