Hi everybody,
  I'm designing a communication system. Given a target BER=1e-12 I know that I need some Eb/No at the input of the receiver, allright. ...but what I'm trying to understand is the minimum SNR that I can deliver to the BERT so that he can measure a BER=1e-12 correctly. Rephrased, how much can I deteriorate the SNR going toward the BERT input? Is this a BERT measurement machine spec?

Thanks
.matteo