HP TM 11-6625-2779-14&P - Manual (Page 39)

Model 3555B Section IV
Figure 5-4. Return Loss Test Set-Up
d. Open S1 and down range the 400FL for an
on-scale indication. This indication
subtracted from the reference established
in step c, is the bridge balance and should
be greater than the return loss
specification.
e. Unplug or disconnect R4 in Figure 5-4 and
connect the 3555B tip and ring in its place.
Be sure to use short clip leads.
f. Momentarily close S1 and recheck the
reference on the 400FL. .Open S1 in
Figure 5-4 and down range the 400FL for an
on-scale indication. This indication must
be down at least 30dB from the reference.
g. Tune the 654A from 50Hz to 20kHz. The
400FL indication must remain at least 30dB
down from the reference.
h. Change the 3555B FUNCTION to
CARRIER 600 BAL and repeat steps f and
g between 3kHz and 150kHz. Return loss
must be at least 26dB down from the
reference.
i. Change the bridge resistors in Figure 5-4 to
900 ohms f 0.1% (use 300 ohms + 0.1% in
series with 600 ohms
±
0.1%) and change
the 3555B FUNCTION to VF/Nm 900 BAL.
Be sure to reset the reference level after
the resistors are changed. Check the
return loss between 50 Hz and 20 kHz.
The return loss must be better than 30 dB.
Figure 5-5. Filter Response Test Set-UP
5-5
FIG 5-1