Installation Guide

4002804 Rev C QPSK (Release A63) Software Upgrade and Installation Instructions 37
What Is the QPSK Range Extension Feature?, Continued
Rule
Description
4
The ranging radius is 0 km to 64 km, with 0 km set at the programmed
cable length.
5
Transport distances are in integer multiples of 31 km, to a maximum of
248 km.
6
All four demodulators are delayed by the same value programmed in
the QPSK modulator.
7
The distance ranges stated in this document are approximate and based
on a velocity of propagation in fiber of 68 percent of the speed of light in
a vacuum (3 x 10
8
meters per second). Corrections to the setting of the
QPSKs should be made where these distances do not apply, as in coaxial
cable.
8
DHCTs closer than the programmed distance value may not range and
may interfere with other DHCTs.
9
The delay distances that appear on the front panel of the QPSK are one-
way path distances and assume an equal distance path on the forward
and reverse connection. It is not necessary for the forward and reverse
path to be the same distance, as long as the total propagation delay
matches the equivalent time delay.
10
It will not be possible to use a co-located DHCT directly connected to the
QPSK modem as a test device for QPSK link verification when the
ranging extension mode is used. This connection violates rule 8.
However, you can test for QPSK link verification with a DHCT directly
connected to the QPSK as long as the reverse path is not active.