Installation Guide

38 QPSK (Release A63) Software Upgrade and Installation Instructions 4002804 Rev C

Activate Range Extension Feature (Optional)

Introduction

This section provides instructions for changing the modulator-to-node distance

settings for the QPSK modulators on your system.

Changing the Distance Settings

If the modulator-to-node distance of the QPSK modulators on your system is more

than 64 km, complete these steps to change the distance settings.

If the hub you are configuring supports existing customers, disconnect the

modulator RF output cable for 15 minutes. Otherwise, go to step 2.

Note: While the QPSK is disconnected, the DHCTs on the hub are not fully

functional.

See the Range Distance Settings Diagram, earlier in this section, to determine

the QPSK range distance settings appropriate for your system setup. Then,

complete the following steps to set the modulator-to-node distances.

a) On the front panel of the QPSK modulator, press the Options button

until the Mod-Node Dist option appears.

b) Select a value of optical fiber length that is less than or equal to the sum

of the actual optical cable length used for distribution to the remote hub,

plus the minimum optical cable length used in the HFC network from

the hub.

c) Adjust the setting if the cable propagation velocity factor is not equal to

68 percent of the speed of light in a vacuum.

d) Press the up and down buttons to choose the desired one-way fiber

delay and Enter.

Results:

 The first time you change the modulator-to-node distance setting from

0 (zero) to xx, the QPSK will reboot.

 The modified code is downloaded to the QPSK modulator and

demodulator.

Reconnect the cable to force all DHCTs on the hub to reestablish a DAVIC

connection with the appropriate time offsets.

Place a DHCT at the closest possible location to where the HFC network

transitions from optics to cable; then, boot the DHCT and press the Power

button.