CHAPTER 3: FIELD APPLICATIONS
MDU Solutions
®
– DVIS/DVISm - Digital Video Insertion System & Mini Digital Video Insertion System - Installation & Operation Manual
3-3
QAM or analog channel), see Figure 3-3. This can be spectrum in the middle of other channels or above the HFC plant
end frequency (at the “band edge”). In these scenarios, a channel is allocated on the system where no carrier is sent from
the headend and every property in the system where the DVIS Device is installed may insert a QAM without the use of a
channel deletion filter. When RF spectrum is available for this application and/or there are a large number of insertion systems
installed, the cost of a channel deletion filter may be saved at every property.
3.3.2 RF QAM Insertion at Band Edge
There are two main scenarios for this deployment:
•
Regular 870 MHz plant has some empty channels remaining unused just below 870 MHz. The new QAM channel is
inserted on one of these empty channels.
•
Plant is built to 750 MHz so at least 100 MHz of plant is available with empty channels. The new QAM is inserted in
this upper band above the 750 MHz plant.
In each case, some extra loss may be incurred through passives that are near or past their usable bandwidth but in such a
case, only a very few passives are affecting the new QAM channel and the output may be increased slightly to compensate
3.3.3 RF QAM Insertion Into Deleted Channel
This application is intended for clear or encrypted QAM channels that have programming that is able to be sacrificed or for
QAM channels that are designed for this program insertion feature. Encrypted programs will be replaced with an ‘in the clear’
program. Using the optional channel deletion filter, the target channel may be effectively removed to make space for the
inserted channel. In this case, Figure 3-4, adjacent system channels are minimally affected through the “Brick Wall” channel
dropping filter technology.
The equipment can be used to insert local programming into an EIA channel where the cable system carries a channel but
providing customers with the programming on that channel is discretionary. In this scenario, a system EIA channel is deleted
using an optional channel deletion filter with very good adjacent channel performance and deep rejection of the intended
deletion channel. This filter is available from ATX Networks and is an integral part of the design of the units. In this case, they
will create a totally new QAM channel and insert it into the blank spectrum following the output of the filter.
Figure 3-4:
Insertion into Locally Deleted QAM
