Agilent Technologies HP 8719D Service Manual page 49

Repeat steps 4 and 5 at least 3 times to look for modes. Modes appear when
6.
a harmonic of the source fundamental frequency is able to propagate through
the cable or connector. It is helpful to be able to plot the trace each thne to
compare several connections If any mode appears each time the cable is
connected and reconnected, measurement integrity will be affected. The
cable connector and/or cable should be repaired or replaced. Refer to the
example plot in F'igure 2-6.
Note
The connector repeatability measurement should be done at the
test port as well as at the end of the test port cable.