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Anritsu FAQs

A coax return loss measurement on my S331D is not passing. How can I tell if the problem is due to a bad coax or if the Site Master is faulty?
Do a visual inspection of all connections on the site master, cal components and test port cable.  Carefully clean all connectors and then re-test.  If the test is still not passing do the following: Calibrate at the site master leaving the load on after the CAL ON is displayed.  The Return loss should be 42dB or better.  With good components and a good Site Master 55-60 dB return loss is typical.  If the Return loss after the calibration is acceptable put the phase stable cable on the Site Master and put the termination at the end of the test port cable.  The typical Return loss of a good phase stable cable should be 30dB.  If you as seeing a 20 RL or less the phase stable cable might need replacing.  Even though you calibrate at the end of the phase stable cable when an RL of 20dB of less on a phase stable cable is not good.  You can also try moving the cable with the load on the end of it after calibration while watching the RL sweep.  A bad cable exhibit wild swing up and down as you move the cable around. If the Site Master calibrates correctly and the phase stable cable looks good try testing a known good coax cable of the same type.  If it this cable looks good then the original coax cable is likely to be the cause of the problem.