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Distributing
Video
I thought
it might be interesting to take a look at the subject of Distributed
Video. This covers a wide range of applications,
from viewing your Satellite, Antenna, VCR or DVD on multiple TV's to Security
Cameras or Baby
Monitors .
And the
nice thing is that they're all pretty much done about the same
way! It's extremely easy if you only have a single source
(like satellite or cable) to distribute. All you (might) need
is a splitter
to connect all your TV's together to your source. I say
"might" because if the signal is split enough times it will weaken
(attenuate) to the point that it needs to be amplified - but we'll get
to that in a minute.
Let's
assume that you have several sources that you want to view
throughout the home: a couple of Security Cams, a Satellite receiver,
and a DVD player. What you'll need to do is choose an unused
channel on your TV for each source. For instance, you might
use channel 3 for the satellite, channel 66 for Camera #1, channel 68
for Camera #2, and channel 70 for the DVD.
In this
case you'll need a 3-source modulator (for the
cameras and DVD player). You wouldn't need to modulate the
satellite receiver since it's (probably) already exiting the receiver
on channel 3. A modulator, in case you don't know
is simply a device that accepts an A/V signal on one channel, and
outputs it on another. Channelvision
makes decent 3 (or more) channel modulators.
One thing
you need to watch for when you're shopping for your modulator is
whether it accommodates line-level inputs or coax.
Again, just to be clear, line-level (also known as RCA in/out) are the
tiny red, white (2 channels of audio) and yellow (video)
jacks. Most DVD players utilize these. Security
cameras may or may not depending on which kind you have - just make
sure you get the right kind of modulator(s) for your needs.
Typically, the modulator will then have an RF (coax) output to inject
all your sources into your CATV cable.
And
another thing: if you're trying to distribute stereo
sound make sure that you have a stereo
modulator so that you don't find yourself
disappointed!
If you
have other sources in addition to whatever runs through the modulator
(i.e. a second modulator, satellite, or antenna), you need a combiner
(sort of like a reverse splitter) to place the multiple sources on a
single cable.
Below is a
diagram from Channelvision that
shows how a typical setup might look:
As
mentioned before, you have to take into account the fact that signal
will attenuate (weaken) the more times it's split. This
diagram shows Channelvision's recommended use of in-line amplifiers
(here a Leviton bi-directional amp), but every situation is different.
For
your info, signal loss is measured in terms of "dB's",
and usually splitters (here the HS-2's)will have the ports marked with
the expected loss which will occur as the signal passes through
it. For instance, a 3-way splitter might have two ports
marked "3.5 dB" and one port marked "7.0 dB." The higher
number indicates that the signal exiting that particular port will
suffer greater loss. You can see in the little chart on the
diagram what the numbers are for distance and for the HS series of
splitters.
Occasionally
in your efforts to boost signal enough to one TV you find TOO MUCH at
another (sometimes indicated by scrolling horizontal lines - looks like
some kind of electrical interference - oh, and by the way, a
snowy picture usually means not enough strength).
Anyway, you can add in-line "attenuators "
or "dB pads" if signal is too strong at a particular
television. So with a little playing around you
should be able to get decent video at all your sets!
The one
last thing you might have noticed from the diagram is the "low-pass
filter " associated with the antenna
feed. This is
just a filter that blocks channels on the higher band (allows only VHF
signals for local channels). In this instance the higher
channels are blocked since they aren't really desired, and would do
nothing more than "walk over" the modulated sources.
I'm not
going to get into all this right now, but once you have all of this in
place (and if you planned ahead with IR control of your TV's &
sources) you can easily integrate this into a whole-house automation
scheme. View people at the door automatically when the
doorbell rings, receive visual notification when the kids get out of
bed, monitor the home when the security system is active - all kinds of
stuff!....
... And
by the way, a lot of this stuff is done for you step by step
in Integrating the
Smart Home & its Owner. Recently completed
and available now online (by itself or together with eBook 1), it's an
illustrated installation of a Stargate-based system - complete with
headaches!
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Copyright 2002 Integratorpro.com.
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