[KAT5] Re: Kat5 versus balun versus component coax

["mark_harrison_uk2" <mph@xxxxxxxxxxxxxxx>]

--- In kat5-users@xxxxxxx, "Jeremy Aston"
<jeremyaston@y...>
wrote:
>
> Hi all,
>
> I really like the idea of using cat 5 to distribute my a/v - I've
> flood wired my place and have plenty of cable to do it with!

> [...]
> quality coax cable plus audio feed (I still have the boards up to do
> it), or using Kat5 hardware or using a component video balun and
> cat5e cable.  I appreciate that the response here may be
> skewed towards kat5 but hopefully Keith or someone else will
> have some argumentation that will explain what the differences
> are and what the pros/cons of each method are.

Jeremy,

Running three coax cables would, in my view, be a poor idea. One of
the problems with component video is that it can be sensitive to
timing errors between the different parts of the signal. Unless you
can be absolutely confident that the cable lengths for all three are
the same, then you may hit timing errors (as ever, light isn't
actually fast enough!)

Using a "component balun" serves two advantages. Firstly, the
good
ones ensure that you have identical length signal paths, because you
are using 6 strands (ie - three pairs) within a single CAT5/6 cable,
and the length is guaranteed to be the same. It's worth noting that
the good ones also have near-on identical length signal paths WITHIN
the items also.

Secondly, that by balancing the signal onto a twisted pair, rather
than using a single cable, you get common-mode noise rejection. Errors
caused by induced voltages on one cable of a given pair will be
cancelled out by the identical error on the other pair, because a
balanced signal sends a normal and an inverted signal, and is
therefore able to work out, and correct for, shifts in the same
direction in each.

You can think of KAT5 devices as active baluns. That is to say, baluns
that also include an impedance-matched amplifer to ensure against
signal strength loss over long cable runs.

What you SHOULDN'T do is use three KAT5 composite baluns for component
- you should get Keith to make you a component one.

Of course, there's actually a third advantage of using baluns, if you
use ones that balance onto CAT5 cable... namely you get the
flexibility of running them wherever you want provided you put enough
CAT5 in, rather than having to make ALL your equipment positioning
decisions at time of the initial install. Granted you aren't likely to
want to move your Plasma once it's mounted, but you may want to move
your DVD player, or replace it with a media server in another room...

The biggest problem I have with KAT5 units is that they aren't CE
approved :-( If this is for yourself rather than a client, then it's
not a problem.

The biggest advantage I see with KAT5 units is the price/performance.
They cost within spitting distance of most passive baluns, for which
you get all the benefits of active operation.

Regards,

Mark Harrison