UNderstanding Rx SNR

First, excuse me for my english, is not my native language and I learned by myself watching Tv and talking with people around USA.

Second, for me, the Rx SNR is the Receiving Signal to Noise Ratio. Is the average in separation from the signal to the noise in dB. Bigger is better because the noise is far from the signal.

But, when the signal has a problem in orig place (Turin yesterday), the Rx SNR shouldn´t change, because the noise from the satellite to MY antenna is the same, is normal (if the problem is in orig).

I assume that this value is that.. noise separation in the reception.... but maybe not. I was monitoring the Viasat when the problem happened yesterday and the SNR was dropping slowly.. why, and it happened to everyone. Th problem in orig is not a RX SNR.... the modem should be connect to satellite but it should´t   get in the Network entry because the link between orig and satellite is broken.

Thank you