Cisco DNCS System Release 2.8 3.8 4.3 Installation Guide

 

4031324 Rev B 

25 

 

With prior versions of software, the Model D9482 QPSK Modulator was capable of 
successfully connecting and operating DHCTs within a distance of approximately 
128 km round trip (64 km each way when forward and reverse paths are equal).  

Note: One kilometer equals 0.621 miles. 

This distance limitation is mainly due to the width of the ranging slots defined in the 
Digital Audio-Visual Council (DAVIC) standard for operation over the hybrid fiber 
coax (HFC) plant.  

The width of the ranging slots limits the maximum distance between DHCTs for 
successful connection and operation. Because the current modulator software 
assumes that the closest DHCT is at the same location as the QPSK modulator, an 
unnecessary limit is placed on the furthest distance that a DHCT can be located from 
that QPSK modulator. 

Some cable service providers would prefer to physically locate the QPSK hardware 
in the headend and extend coverage to DHCTs that are farther from the QPSK 
modulator than the currently allowable maximum distance.  

This optional feature for the Model D9482 QPSK Modulator allows Explorer DHCTs 
to sign on to the system and operate properly at extended distances from the QPSK 
modulator. (This feature provides the resolution to CR 6922.) 

Using the front panel of the QPSK modulator, you can select one of nine different 
values of one-way range extension. The front panel displays the extension distance 
in kilometers.  

Note: Though it is not possible to extend the maximum distance between the 
DHCTs, which must remain within 64 km, it is possible to delay the timing within 
the modulator such that the distance to all DHCTs can be extended. This software 
feature allows you to extend the distance to the closest DHCT from 0 km to 248 km, 
one way, in steps of 31 km.