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measurement uncertainity of 85108A VNA

Question asked by punamtyagi on Mar 13, 2006
Latest reply on Apr 5, 2006 by BillKwan
I am using a 85108A VNA for measuring an amplifier(5 GHz, 300 MHz bandwidth ,gain 33 dB) under pulsed condition ( pulsed width 20 micro sec).I am getting the gain , but measurement is not repeating even after one minute.The S21 mag (dB) difference is between .3 to 1.1 dB between successive measurements.I want to know wether this deviation is because of the in built uncertainity of the VNA. What is the worst case uncertainity in S21 (mag and phase) for 85108A under pulsed condition ( i am using external triggering).The same amplifier is working fine under CW condition and results are repeating under .2 dB.