Functional Block Diagram - Blonder Tongue Laboratories Inc.

Broadband Specification Guide
Cherry Picking From a Cable TV Feed
Functionality
This system will allow you to select a few desired channels from the local cable TV company and ignore all of
the other undesired channels. This signal can now be handed off to a traditional coaxial distribution network
or a hybrid fiber / coaxial distribution network within the facility.
In Depth Description
There are two different sets of electronics that can be employed to create the desired channel line up. The
first method is to employ a channel processor. Channel processors come in several different versions, but all
do basically the same thing, they take one channel on the input, and convert it into another on the output. If
the channel line up is known well in advance, fixed processors can be used to minimize cost. The downside of
fixed processors is that if the local cable TV company changes it’s channel line up, another processor would
need to be purchased.
Agile processors are able to change both the input, and the output channel on the fly to be able to
accommodate any changes that might be necessary. The keys to success in this system are making sure that
the processors have enough input signal to function correctly and making sure that the output levels are all set
correctly so the channels do not interfere with each other.
The second method is to employ a demodulator and modulator in series. The demodulator is an agile device
that can be set up to receive a TV channel input signal. Its function is to extract the audio and video information
from the RF carriers and provide separate audio and video output signals. These separate audio and video
feeds, also called baseband audio and video, are then applied to a modulator. It is the job of the modulator to
take the audio and video and make them in to a cable TV channel. This channel can then be combined with
other channels that have been created at the property. The keys to success in this system are making sure
that the demodulators have enough input signal to function correctly and making sure that the modulator is
adjusted correctly for proper modulation and output levels.
If you pick one product from each category on the following pages, you will have all of the components to
ensure a working design. Once all of the products are identified, the specifications can be looked up in the
specification library at the end of this publication.
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