effect of SMA in HFSS simulation

Hey,
I am interested to know what effect will adding a sma plug into the simulation do. Will it make a hugh difference or not. we simulated a antenna with hfss but when we did the anachoic chamber test the results were off a little and the s11 was also off. I have the SMA up through the bottom of the pcb board i also have a cabling running off it as well But how much is too much simulation that is my question.

regards daniel