[Elecraft] Re: K3: listening to both rcvrs - Reduced receiver

[Phil & Debbie Salas]

"That is true if the two receivers are tuned to the same passband and
you are using an identical antenna for the two receivers.

In the case of receiving split, you are not looking at the same noise
entering the two receivers.  In this case, by combining two different
passbands, the desired signal would only come from one receiver but
the summed noise would come from both receivers, dropping the SNR by 3
dB."

Chen is correct.  Back in my microwave telecom days, we used to combine two 
receivers from two different microwave antennas both for multipath 
improvement, and for S/N improvement.  The desired main signals from both 
receivers are highly correlated, but the noise is still uncorrelated 
(different antennas, slightly different passbands/filter characteristics). 
So the main signal improves in strength 6dB (adds on a 20log basis), but the 
noise improves 3dB (adds on a 10log basis).  The result is a 3dB S/N 
improvement.
Phil - AD5X