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Topic:
Grounding Shielded Twisted Pair
This thread has 35 replies. Displaying posts 16 through 30.
Post 16 made on Saturday September 1, 2018 at 15:51
Ernie Gilman
Yes, That Ernie!
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On September 1, 2018 at 10:59, highfigh said...
I was asking for a simple answer, but OK.

You asked a question so simple that there was no simple answer, unless you would accept "Yes and no" or "Depends" as an answer. I thought those answers wouldn't help. My answer didn't leave it at one or two words but instead described the conditions under which "Yes" and "No" would be accurate answers.

Does it strike you as strange that most source devices don't have a grounded power cord and receivers, preamps and some integrated amplifiers do?

No. This completely avoids problem ground loops through the power cord and chassis. Note carefully that I said PROBLEM ground loops.

Ever measure the resistance from the ground ferrule on a source device and its chassis? They're often separated. I've seen that. I've seen a power amp (Citation 12) with a small resistance between amp ground and chassis. And when a capacitor got leaky, that resistor just smoked right up!


If the system is more simple and consists of a receiver with preamp out to a separate amplifier,

I should probably stop writing here since I don't know of a system with a receiver (which has a preamp in it, that is to say, source selection, volume, etc) WITH a preamp (unless you mean to say that the receiver has a preamp, which they all do)... so I'm not sure what you're talking about.

it could be said that the receiver is the source- that's the reason I asked in the way I did. Even a preamp and separate power amp that have grounded power cords and use XLR connections can have ground a loop, under the right conditions (or wrong, depending on how the building was wired)- I worked on a house with this condition when I installed a Krell preamp and power amp, using Canare cables. Changing to unbalanced cables cured it completely.

This probably has to do with how the ground was handled in the balanced wiring. It's definitely not true that an unbalanced connection, which gave you success here, is a better way to connect than balanced. As you say, there's no single method that works best in all situations. That's because each situation has certain things built into it that can make a good connection system have a problem.

Why did I use the word PROBLEM up above? The average system has many ground loops. The easiest to visualize is the analog audio connection of a player to a receiver or preamp or processor. There are two channels, and the ground of each channel of the player is connected to the ground of each channel of a preamp input. That's a ground loop.

We don't care about and don't even perceive ground loops until they cause a problem.
I'm sure you have seen this- there's no single method that works in all situations.

[Link: rane.com]

I know thjs is now a long discussion. Still, I bet you would not have wanted me to answer "Yes and no" to your original question!
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 17 made on Saturday September 1, 2018 at 18:16
highfigh
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On September 1, 2018 at 15:51, Ernie Gilman said...
You asked a question so simple that there was no simple answer, unless you would accept "Yes and no" or "Depends" as an answer. I thought those answers wouldn't help. My answer didn't leave it at one or two words but instead described the conditions under which "Yes" and "No" would be accurate answers.

No. This completely avoids problem ground loops through the power cord and chassis. Note carefully that I said PROBLEM ground loops.


I should probably stop writing here since I don't know of a system with a receiver (which has a preamp in it, that is to say, source selection, volume, etc) WITH a preamp (unless you mean to say that the receiver has a preamp, which they all do)... so I'm not sure what you're talking about.

This probably has to do with how the ground was handled in the balanced wiring. It's definitely not true that an unbalanced connection, which gave you success here, is a better way to connect than balanced. As you say, there's no single method that works best in all situations. That's because each situation has certain things built into it that can make a good connection system have a problem.

Why did I use the word PROBLEM up above? The average system has many ground loops. The easiest to visualize is the analog audio connection of a player to a receiver or preamp or processor. There are two channels, and the ground of each channel of the player is connected to the ground of each channel of a preamp input. That's a ground loop.

We don't care about and don't even perceive ground loops until they cause a problem.
I know thjs is now a long discussion. Still, I bet you would not have wanted me to answer "Yes and no" to your original question!

My question could have been answered with "No, I mean the devices that are the source of the signal", but you had to go all War And Peace on me.

Your comments about the receiver are very odd. I guess we need to be more explicit- I meant 'a receiver with preamp output jacks'.
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 18 made on Saturday September 1, 2018 at 21:37
Ernie Gilman
Yes, That Ernie!
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30,104
Here's what happened. You wrote "a receiver with preamp out to a separate amplifier." Now that you've clarified it, I see that you wrote exactly what you meant. I didn't combine the words (parse the phrases) the way you meant them. I read
A receiver
with preamp
out to a separate amplifier.
If you had written "a receiver with* Preamp Out to a separate amplifier," I think i might have gotten it. Words. Damn 'em. Can't write with 'em, can't write without 'em.

*or "using Preamp Out to a separate amplifier" or "with its Preamp Out to..." or maybe even "with its preamp out...."
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 19 made on Sunday September 2, 2018 at 09:58
highfigh
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On September 1, 2018 at 21:37, Ernie Gilman said...
Here's what happened. You wrote "a receiver with preamp out to a separate amplifier." Now that you've clarified it, I see that you wrote exactly what you meant. I didn't combine the words (parse the phrases) the way you meant them. I read
A receiver
with preamp
out to a separate amplifier.
If you had written "a receiver with* Preamp Out to a separate amplifier," I think i might have gotten it. Words. Damn 'em. Can't write with 'em, can't write without 'em.

*or "using Preamp Out to a separate amplifier" or "with its Preamp Out to..." or maybe even "with its preamp out...."

How long have you been working with consumer AV equipment? If you haven't seen a receiver connected to a power amp, another receiver, preamp or integated amp to make a system control other speakers and add power to the overall output, they must do things differently where you have lived. This is not a rare configuration (although you may never have seen it), especially when people want to use what they have, rather than spring for more or new equipment. Even the REC Out can be used if the power amp has some way to vary the level.

Geez!
My mechanic told me, "I couldn't repair your brakes, so I made your horn louder."
Post 20 made on Sunday September 2, 2018 at 11:11
Ernie Gilman
Yes, That Ernie!
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Sure, I've seen all of that. And every time the two words "preamp output" or "preamp out" have been used to mean what you meant, they have either been capitalized or written as "the preamp output." Try substituting those tiny changes to what you wrote and see that the meaning is more clear.

You seem to be stuck on thinking that what you wrote could not have been misinterpreted, but it could. It's not enough for us to look at what we write and judge that we, who know what we mean, can understand it. Communication requires that we look skeptically at what we write, after having written it, to see if perhaps a person might not get what we're talking about. Omitting capitalization of terms usually capitalized is a way not to get the meaning across.

For that matter, did you read it after you wrote it, to see if it was clear?
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
OP | Post 21 made on Sunday September 2, 2018 at 16:19
InVision Systems
Long Time Member
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119
This thread literally turned into exactly what I was hoping that it wouldn't turn into. Every thread on this subject across virtually every forum ends in the same. But no one answers the question. I'm starting to think that this subject is a "pink unicorn" in which everyone has a different opinion on.

So do we have anyone who has terminated shielded category cable that lived to tell the story?
Elevate Technologies
Nashville, TN
Post 22 made on Sunday September 2, 2018 at 19:27
lippavisual
Senior Member
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December 2007
1,458
If the end device doesn’t have a grounded Ethernet port, then stp will not make a difference for the device. Stp, at that point, will only gain you a little extra interference rejection because of the foil.

Your question still doesn’t make sense though. The other end of your cable can be terminated with shielded RJ45 or jack.
Post 23 made on Sunday September 2, 2018 at 21:09
Ernie Gilman
Yes, That Ernie!
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lippa, many questions have been asked here. Exactly which one are you referring to in Post 22?

Let me point out again that Brent McCall has said that shielding of CAT cable introduces problems that don't exist with UTP. It's not simply the case that shielding will gain a little bit more interference rejection. For instance, shielding introduces more capacitance per foot between conductors.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
OP | Post 24 made on Sunday September 2, 2018 at 22:01
InVision Systems
Long Time Member
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On September 2, 2018 at 19:27, lippavisual said...
If the end device doesn’t have a grounded Ethernet port, then stp will not make a difference for the device. Stp, at that point, will only gain you a little extra interference rejection because of the foil.

Your question still doesn’t make sense though. The other end of your cable can be terminated with shielded RJ45 or jack.

Lippa,

The question is in relation to grounding the stp at both ends. The shielded RJ45 connector and jack generally have a physical connection to ground the shield and drain wire. I understand that you only want to ground on one end. If I actually earth ground at the patch panel, at which point is the other end of the cable get grounded? It sounds like your saying that if I ground at the patch panel, connect the shield and drain to the RJ45 or jack, use a shielded patch cable into the device, and the device has a grounded ethernet port than I will be grounded at both ends. Is that what you are saying?
Elevate Technologies
Nashville, TN
OP | Post 25 made on Sunday September 2, 2018 at 22:05
InVision Systems
Long Time Member
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On September 2, 2018 at 21:09, Ernie Gilman said...
lippa, many questions have been asked here. Exactly which one are you referring to in Post 22?

Let me point out again that Brent McCall has said that shielding of CAT cable introduces problems that don't exist with UTP. It's not simply the case that shielding will gain a little bit more interference rejection. For instance, shielding introduces more capacitance per foot between conductors.

He is referring to the actual question of the thread. Ernie, I appreciate your participation but the goal of a question is to arrive at an answer. You seem to be trying to take the conversation in circles. I certainly appreciate your input, but it's not answering the question.
Elevate Technologies
Nashville, TN
Post 26 made on Sunday September 2, 2018 at 22:37
Ernie Gilman
Yes, That Ernie!
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Well, to back up some, then, question your understanding that you only want to ground the shield at one end. This is not true of all kinds of shield connections. What makes you think it's true of this application?

And I should have started by asking what you mean by accidentally grounding the display end of the run? Were you trying not to ground both ends but you grounded both ends and you want us to figure out how you did it?
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
OP | Post 27 made on Tuesday September 4, 2018 at 16:23
InVision Systems
Long Time Member
Joined:
Posts:
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I've actually done nothing but run some wire at this point. In my research, it seems the common practice is to only ground one end of a shielded twisted pair. I'm actually having a hard time understanding how the other end gets grounded. So I am looking for some detail from those with experience terminating shielded twisted pair.
Elevate Technologies
Nashville, TN
Post 28 made on Tuesday September 4, 2018 at 17:34
Ernie Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
30,104
Start by checking all wiring instructions for products you're using. If you're told to use UTP, call and ask them if STP causes any problems, and if so, how to wire it.

You haven't yet told us what equipment you're using so we can't even look it up ourselves for you. Different stuff requires different stuff.

By the way, Post 2 pointed you in the right direction.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
OP | Post 29 made on Tuesday September 4, 2018 at 18:15
InVision Systems
Long Time Member
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Posts:
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119
Ernie,

What would you be looking up, my friend? As I mentioned, I spoke to a manufacturer's rep from JAP that recommended STP. I'm not interested in going down the road of whether I should use STP or UTP. I have both in this install.

My question is simple. If I intend to ground STP at the patch panel, and I intend not to ground at the end of the run, how should it be terminated exactly? (assuming that I might terminate to a keystone jack or RJ45)
Elevate Technologies
Nashville, TN
Post 30 made on Tuesday September 4, 2018 at 19:58
Ernie Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
30,104
Is this the sort of thing you were looking for?


The following is a lot of an article published in August of 2013 by someone WAY THE HELL ahead of me! It's at [Link: siemon.com]

A standards-based UTP network cabling system requires no path to ground. However, according to ANSI-J-STD-607-A “Commercial Building Grounding (Earthing) and Bonding Requirements For Telecommunications”, screened and shielded cabling channels are required to be bonded through a conducting path to the Telecommunications Grounding Busbar (TGB) in the telecommunications room (TR). Like UTP systems, F/UTP and S/FTP horizontal cable is terminated to outlets at the work area and in the TR. Screened and shielded connector designs, such as Siemon’s Z-MAX™ 6A Shielded and TERA® outlets, automatically ground to the patch panel in the TR during installation, without the need to individually provide a ground termination for each outlet. The only additional step required to ground these F/UTP and S/FTP cabling systems is to connect a 6 AWG wire from the ground lug provided on the patch panel to the TGB.

The recommended grounding sequence is as follows: the , the outlet self-grounds to the patch panel, and then the panel is grounded to the equipment rack or adjacent metallic pathways. The basic sequence is reflected in the diagram below.



1. F/UTP cables screen or the S/FTP shield is terminated by the outlet
2. Outlet makes contact with patch panel’s grounding strip as outlets are snapped into place
3. Panel is grounded to equipment rack or adjacent metal pathways via a 12 AWG wire attached to panel ground lug
4. 6 AWG ground wire connects rack to the TGB

A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
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