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#481686 06/20/09 05:04 AM
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sph Offline OP
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From Muxlab:

Cat5 vs Cat6

Notice point #8 where Muxlab has actually found a higher skew when using cat6 cable. Could this be because cat6 has more twists/foot and therefore a higher probability of differences in twist rates among pairs? I would think a higher quality (=more expensive) cat6 would have more uniform twist rates among the pairs.

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#481687 06/21/09 02:39 AM
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I think this emphasizes the point that many of us have tried to make for years:

One size does NOT fit all.

There has been a trend in recent years toward installing Cat 5E/6/6A for everything.

Personally I don't think it's a good idea.

I think Voice should be on Cat 3 cable and terminated on 66 or Krone Blocks.

I think T-1 should be on Shielded Twisted Pair and terminated on RJ48X jacks.

I think Audio should be run on Stranded wire, color coded for Audio (Blk/Red etc.)

I haven't done enough video recently to comment on video baluns, but I will make this comment in general:

I would always prefer to use the product that the equipment is designed for rather then use a transformer/balun/converter with some other wire.

This doesn't mean there's no place for those units. Of course there is. And I have used them successfully and efficiently many, many times.

That doesn't mean I'd rather use them then the original product. As far as I'm concerned the original product is always best. Sometimes it's not efficient or affordable to use it, but that doesn't mean it's not as good.

Cat 6/6A is an excellent, relatively inexpensive medium for LANs running at high speed. Where is it written that it should be the medium of choice for everything?

Sam


"Where are we going and why are we in this hand basket?"
#481688 06/21/09 04:28 AM
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That's been well known for years. Most manufacturers want you to use CAT5, NOT even CAT5e.

And I wish they would stop calling these things baluns. This is getting to be like the infamous RJ-45. They are media converters!

A balun is a simple transformer device to change an unbalanced line into a balanced one. Hence the name balun= BALanced UNbalanced.

-Hal


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#481689 06/21/09 02:33 PM
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Baluns are pretty much known as Balun media converters or Balun for short. A balun takes an balanced signal like in coax where you have a single conductor balanced around ground and converts it to a unbalanced signal like in twisted pair where you have two wires in use. RJ45 is a technically incorrect term but Balun isnt or am I confused? :confused:

#481690 06/22/09 04:08 AM
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I think that you have it backwards, tito. Coax is generally unbalanced cable, exactly because the size of the conductors (and therefore certain electrical characteristics of same) are different. UTP is generally considered balanced.

There are also "baluns" that as Hal said, should be just called media converters as they join balanced (or unbalanced) cables at both ends.

Sam, as you know the choice of UTP for audio and video became feasible as the newer category cables certified at frequencies where video could be transmitted. That's why I posted the article, because it represents a conundrum, ie higher CAT=higher bandwith=higher resolution but also equals (negatively) higher skew. Notice that baluns are incidental to this article and have nothing to do with the cable skew problem.

#481691 06/22/09 04:58 AM
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Quote
Originally posted by sph:


Sam, as you know the choice of UTP for audio and video became feasible as the newer category cables certified at frequencies where video could be transmitted. That's why I posted the article, because it represents a conundrum, ie higher CAT=higher bandwith=higher resolution but also equals (negatively) higher skew. Notice that baluns are incidental to this article and have nothing to do with the cable skew problem.
I agree. I put the Balun/xfrmr/media converter item in there because to use a different type of media - you need a converter.

The cable manufacturers have been working there butts off, trying to squeeze higher and higher bandwidth out of what is essentially copper telephone wire. The methods that they use allow for higher bandwidths - but that doesn't mean that these cables will now provide better service for a non-Lan application then the media that was designed to run that application.

Years ago, my first exposure to this was with IBM Mainframes. We would connect IBM 3270 terminals to a cluster controller via RG-62 coax. With the use of a Balun we could use existing Cat2/3 telephone wire. It worked fine and was significantly easier to use then the coax.

We connected WYSE terminals that called for an asynchronous serial cable connection with telephone wire and line drivers. They also worked beautifully.

Hell, I've put 4160Volt transformers on a run because we needed 480 Volts at the top of a building and the cost of getting enough pipe up 20 stories was excessive.

Just because a media converter works in some situatons doesn't mean it will work in others.

I still stand by what I said. One size does not always fit all.

Sam


"Where are we going and why are we in this hand basket?"
#481692 06/22/09 07:16 AM
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Yup, I got them backwards. frown

#481693 06/22/09 08:14 AM
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Quote
Originally posted by Silversam:
Years ago, my first exposure to this was with IBM Mainframes. We would connect IBM 3270 terminals to a cluster controller via RG-62 coax. With the use of a Balun we could use existing Cat2/3 telephone wire. It worked fine and was significantly easier to use then the coax.

We connected WYSE terminals that called for an asynchronous serial cable connection with telephone wire and line drivers. They also worked beautifully.

Hell, I've put 4160Volt transformers on a run because we needed 480 Volts at the top of a building and the cost of getting enough pipe up 20 stories was excessive.
Well smile You bring back some memories, not all of them good. A lot of computer people have forgotten WYSE (assuming they're old enough to have known them). And to make things even more muddy, IBM also used balanced coax (twinax) in certain applications.

Other than that, we're in agreement. I didn't want to make the post a pro/con examination of the "UTP everywhere" philosophy. And I don't believe that coax will just disappear overnight. After all, cable operators these last few years came up with a scheme called MoCA (Multimedia-Over-Coax) that purports to use the "Coax everywhere" philosophy smile and looks suspiciously like an enhacement of the original so-called "thinnet" ethernet that used RG-58 back in 1970s and 1980s.

#481694 06/22/09 10:12 AM
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SPH -

I put in a lot of twinax, Also that dual coax Wang system - one BNC & one TNC. And all soldered!

Cable folk like that idea (MoCA) because it's what they use for a network - a Bus Topology. And yes it does resemble the thinnet network. But that wasn't the original ethernet. Before that it was "Thicknet" or "Goldenrod" - big fat coax run in a loop around the office. Individual host computers were connected to the bus with connectors called "vampire taps". eek

Personally I think that Bus Topology bites as a network - it's got too many possible failure opportunities. (Class E Fire Alarms also follow the same topology and I think that's really a danger - but no one really cares what I think anyway) laugh

And yes, I agree with you - coax ain't going nowhere. DS-3s go in with coax and while that might not register on a lot of people's radar, in some locales we do a LOT of DS-3 (everyone who can't bear to spring for fiber). When I did CNN's studios in Rockefeller Center, video went in on Coax and they had multiple screened Cat 6 cables at every desk!

Maybe I'm biased. Or more likely just old and cranky.

Sam


"Where are we going and why are we in this hand basket?"

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