We always take 2 test in vswr machine one for distance to fault
Another one for measure match ( frequency )
If u are calibration the bird machine or any machine at 1800 .
You suppose to do the this thing .
First calibration must be full .
Second test the frequency by press on auto if its gave u more them 1.5 for limit line means the feeder is dirty at contactor .
Third distance to fault u must see the damage in connecter or feeder some time the contactor not preparing good and must be less them 1.05 for limit line