# S parameters LT SPICE

I read the help section on .net and found that i can use either a node (Vout) or a resistor (I(Rout)) to specify the output node. However the 2 give me different values of S parameters for the below cct.

For this the value of S11 was -868.46102mdB. While for the directive .net I(R2) Vs the value of S11 was -827.8537mdB which is the correct value. Can someone explain why?