HP TM 11-6625-2779-14&P manual Return Loss Test Set-Up

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 5-4and 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 5-4and 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 5-4to 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.

FIG 5-1

Figure 5-5. Filter Response Test Set-UP

5-5