TV Cabling / CAT 5

[Glen Zook]

First of all, "CAT 5" is not normally used for TV
distribution.  Also, a "Category 5" installation
involves a lot more than just using a category 5 rated
cable.  Unfortunately, the telephone company will
install "cat 5" cable using category 2 installation
practices which makes it not any better than the old
POT ("plain old telephone") installations.

A category 5 cable consists of 4 pairs of solid
conductor wires, each pair twisted together in a
certain pattern (each pair is different from the next
pair in terms of twist).  These 4 pairs of wires are
then twisted together in another series of patterns.
When running between pieces of equipment, wall jacks,
etc., a MAXIMUM of 1/2 inch of wire can be exposed
outside of the sheath of the cable to make the
connections (usually to a 110 type of "block" or
special terminals on jacks, etc.).  Technically, you
can have more wire exposed IF you DO NOT change the
"twist" of the wires.  However, this is a "catch 22".
If you remove any of the sheath, then the twist IS
affected.  Thus, you can remove more than 1/2 inch,
but you then affect the twist and have to shorten the
wires to a maximum of 1/2 inch!

A category 5 installation cannot have any splices in
the cable run, cannot have any cuts or abrasions of
the sheath, cannot come in contact with any other
cables except for other category 5 cables, etc.  There
are special installation hardware available for
installation.  The cable cannot come in contact with
any conductive material except for conduits that
contain only category 5 cable, and the cable must be
inside the conduit, not "taped" on the outside.

Care must be taken to properly install the cable in
order to maintain the "speed" at which data
transmissions can be accomplished.  Category 5 is
rated at a minimum of 155 MBs, and, if properly
installed, can do even better than that.  It is the
"twist" of the wires that allows the high speed data
transmission without any problems.

You might want to take a look at www.bicsi.org for
information on the various categories of
telecommunications cable.  BICSI (Building Industry
Consulting Service International) is the
telecommunications industry professional organization
that is basically responsible for such standards.
They also sponsor various professional and technical
certifications ranging from apprentice installer to
the RCDD (Registered Communications Distribution
Designer) which is "akin", but not the same as, a
Professional Engineer certification in the
telecommunications field.  The RCDD is recogized on a
world wide basis whereas the PE is only recognized on
a single state basis.  Also, the "pass rate" for the
RCDD is not that great (meaning that a smaller
percentage of those who take the examinations pass and
are certified).

Category 5 wiring must be a "straight shot" from the
equipment (i.e. PC) back to the LAN equipment located
in the telecommunications closet (or other entry point
or sub-distribution point).  You are not allowed to
connect other cables in parallel like you can do with
the ordinary telephone connections.

Now, if what you are really doing is just wiring your
house for telephones, you can most certainly use
category 5 rated cable installed in the "normal"
telephone installation ways.  But, all that you will
have is a POT installation that uses more expensive
cable!  Also, depending on the manufacturer of the
cable, you can get some widely varying capabilities.
Some cable barely meets specifications (in fact, I
doubt that some of it even meets specifications) while
other manufacturers produce cable that greatly exceeds
minimum specifications.

Now, for distribution amplifiers and 75 ohm coax:
Unfortunately, the vast majority of distribution
amplifiers cause all sorts of TVI problems even with
relatively low powered amateur radio transmitters.  If
at all possible, use the best TV antenna that you can
get and only use passive "splitters" for the cable
connections to each room.  If you are off of a cable
TV connection, then the signal level should be
sufficient that you will have no problems with signal
levels and definitely will not need an distribution
amplifier.

Also, installing "high pass" filters on each TV set
will help with TVI.  You can get some pretty
inexpensive ones from Radio Shack that actually do a
good job.

Glen, K9STH
RCDD 032053
FCC PG-10-23542
PCIA 109494


--- Mike K5MLC <K5mlc at AOL.COM> wrote:

does anyone have any experience with distribution amps
for cable tv?? I am residing my 40 year old house (the
2nd story has old wood that has had it!) and re-wiring
for cable and CAT 5 into each bedroom while I'm at it.

=====
Glen, K9STH

Web sites

http://home.attbi.com/~k9sth
http://home.attbi.com/~zcomco

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