Are You Installing Cable Or Engineering Performance

Perfect-looking terminations and clean certification results can still hide the interference that slows networks weeks later. We break down EMI, RFI, and crosstalk in plain terms, then lay out the practical install rules that protect performance and your reputation. 
• why EMI is invisible but disruptive to Ethernet signals 
• common EMI sources on job sites, from lights to motors to transformers 
• the real cost of downtime and why customers only remember performance 
• how crosstalk differs from EMI and where it comes from 
• near-end, far-end, power sum, and alien crosstalk explained 
• termination mistakes that create marginal passes and failures 
• Cat 6A, higher frequencies, and the cable combing debate 
• prevention rules: separation, preserving twists, pathway fill, and bend limits 
• cable tray and bundling tips, including PoE heat concerns 
• shielding done right with proper bonding and grounding 
If you're watching this show on YouTube, would you mind hitting the subscribe button and the bell button to be notified when new content's being produced? If you're listening to us on one of the audio podcast platforms, would you mind leaving us a five-star rating? I'd love to hear from you in the comments below what's the worst EMI or crosstalk issue that you've ever encountered in a project. Drop your story in the comments below. 

Transcript

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Welcome And How To Support

0:00

Hey wonder monkeys, welcome to another episode of Let's Talk Cabling. This week we're talking EMI and crosstalk. Stay connected. Do it into the show where we tackle the tough questions submitted by installers, estimators, apprentices, project foremen, project managers, estimators, designers, we are connecting at the human level so that we can connect the world. If you're watching this show on YouTube, would you mind hitting the subscribe button and the bell button to be notified when new content's being produced? If you're listening to us on one of the audio podcast platforms, would you mind leaving us a five-star rating? Those simple little steps help us take on the algorithm so we can educate, encourage, and enrich the lives of people in the ICT industry. Wednesday nights, 6 p.m. Eastern Standard Time, what are you doing? You know I do a live stream where you get to ask your favorite RCDD, you know my favorite, on all those favorite social media platforms. TikTok, Instagram, Facebook, LinkedIn, YouTube, everywhere. But I can hear you, but check them, dragging my dragon, right there, nice. Breathe in, breathe out. I record them so you can watch them at your convenience. And finally, while this show is free and will always remain free, would you click on that QR code right there? You can buy me a cup of coffee. You can even schedule a fifteen minute one on one call with me, after hours, of course. So let me ask you one

When Green Checks Still Fail

1:56

question. Have you ever worked on a project where everything looked perfect? The terminations looked good. The certification tests, they have the big old green check. The customer even signed off on it. But yet a few weeks later, all of a sudden, the phone rings, the network's slow, applications are dropping, video calls are freezing, and the IT department, we're kind of frustrated because the cable you installed just isn't working right like you promised. The customer wants answers. And everyone is pointing fingers. Who are they pointing fingers at? Us the cable guy. Well today we're going to talk about one of the biggest hidden causes of network performance problems. Electromagnetic interference, also known as EMI. And the other forms of EMI, of crosstalk. Now this is one of those topics that sounds technical, but once you understand it, you'll start seeing examples of it on every job site you visit. So grab your favorite beverage, settle in, and let's talk about EMI. Oh, and let's not forget RFI, radio frequency interference.

EMI And RFI In Plain English

3:05

You know, one of the challenges with EMI is you can't see it. You can't hear it. You can't smell it. But it absolutely will impact the performance of your cable plant. Okay? Think about it this way. Imagine sitting at your favorite restaurant, having dinner with your wife on Valentine's Day, and you're trying to have a conversation with her, and then all of a sudden a group of people sit down next to you, and one person starts talking loudly, like I tend to do sometimes, right? And then another, and then another, and then another. Pretty soon you're struggling to hear the person that you're trying to have that conversation with. The conversation is still happening, but the noise around you is making it so difficult, so hard, that it's it becomes unmanageable. That's exactly what EMI does to a data signal cable. Your cable is carrying information from one device to another device. And EMI introduces unwanted electrical noise that interferes with that signal. Now, where does EMI come from? It is all around us. It's the fluorescent lights in your office buildings. It's the electrical motors in your industrial plants. It's the transformers, you know, the big green boxes that go hmmm in the telecom room. Yeah, those are transformers. Variable frequency drives, generators, elevators, power cables, industrial equipment, welding equipment. You may have think of Chuck, I'm doing more cabling in commercial office buildings. Not too much welding equipment there. Well, guess what? You might do work in an industrial environment. But also let's not forget copiers. Let's not forget printers. Anything that generates electrical energy has the potential to create electromagnetic interference. And in some environments, especially like in manufacturing plants, hospitals, airports, and industrial facilities, EMI can be everywhere. Again, hospitals, they have MRI machines. Manufacturing plants, they have you know high power machines that stamp things out of metal. Not only is it a vibration issue, it's an electromagnetic instance. Airports, they got all kinds of radio frequencies floating around at airports. I have a friend who actually was one of the designers at an airport until, well, a few years back. And he could probably tell you there's a lot, a lot of EMI and RFI that you got to concern yourself about at airports. I

Hidden Costs Of Noise And Downtime

5:47

remember walking into facilities, sometimes on job sites, you could almost predict where the problems would occur. And as soon as I saw those large motors, those machineries, I knew we needed to pay attention. We knew that we needed to pay attention carefully to our cable routing because if we ignored it, somebody eventually was going to have troubles with the performance of their cable. And how do you price how do you price downtime because of poor cable problems? How how do you how do you price for a customer? How do they figure out how much money they're losing? Because instead of taking 15 seconds to download an image, it takes 30 seconds to download an image times the number of employees. There's a huge impact to your network if it's not set up correctly. And here's the thing if you ignore it, it's not going to go away. It's going to become somebody else's issue. Especially when you start talking about troubleshooting and performance issue, common mode issues, differential mode issues. Those all affect the computers and how they perform. And troubleshooting always costs more than doing it correctly the first time. Now here's an important lesson for technicians. The customer never sees the effort it takes to fix a problem later. They only remember that their computers didn't work, that their people couldn't process invoices, that their salesmen couldn't make sales calls, that the computers kept rebooting. That's all they're going to remember. They're not going to remember the effort that you put into that cable plant. You know, a lot of people don't realize this. Your reputation is built on performance. That's important if I'm going to say it again. Your reputation is built on performance. Not only how fast you got the cable installed, but also understanding why EMI matters.

Crosstalk Basics And The Toner Trick

7:45

But you know, the EMI is not the only source of interference. Sometimes the cable causes itself to become the problem. And that's where we start talking about crosstalk. And crosstalk comes into that picture. Because you see, EMI is defined as how much one electric or electronic device interferes with another electric or electronic device. I'll give you an example of EMI that probably most of you in this room, or most of you listening to this podcast, you could probably relate to. I know this never happens, but let's step in the realm of dreamland, do do do do do do do do do, where everything is done correctly. And let's just say that uh uh you know you walk into the telecom room and there's a bundle of cables hanging down from the ceiling. Okay, hanging down from the ceiling. And let's just say, again, I know this never happens, let's just say that the the new guy forgot to label some of those cables. Well, how are you gonna figure out what goes where? You're gonna take the you're gonna take your toner, go plug it in the work area outside, you're gonna take your probe, your wand, your banana. Everybody calls it something different, and then what you're gonna do is you're gonna turn this on, right? There it goes. You're gonna turn it on, you're gonna stick it in the bundle, and then it's gonna be soft at first, but then all of a sudden it's gonna get real loud. Yeah, it's gonna get real loud. That's the cable that has the tone. You see, EMI always has three components an interfering source, a susceptible unit, and a coupling between those two. In the example that I just gave you, the cables, the susceptible units were the other cables. The interfering source was the cable with the tone. The separation was the coupling between those two. The further apart those two are, the less interference you have on the susceptible units. No, separation is probably one of the easiest ways to get rid of EMI, because you literally just separated. But there are other ways. You can use metallic barriers, shielded cables, full cables, conduit. Conduit is the the best way to get rid of EMI, but it's also chha ching, the most expensive. So, you know, so that's the way you the way you get rid of EMI is separation or some type of metallic barrier. So let's talk about why is this important?

Ethernet Pairs And Crosstalk Categories

10:06

Because when you look at a cable being used for Ethernet, we're gonna focus mostly on Ethernet. But you know what? The term crosstalk comes back from the old telephony days. In the old the old days, you know, you could pick up a phone sometimes and you could hear another faint conversation on your phone. Distance, kind of like all it sounded like it was off in a distance. That's crosstalk. Somewhere in the cable plant, two pairs were close enough to each other they're causing interference with each other. That's where the term crosstalk comes from. So let's talk about Ethernet in today's show. Ethernet comes in a couple different variants. The most common type of Ethernet is the type that comes that uses two pairs, lands on pins one, two, three, and six. That's going to be used for your hundred meg, your one gig, your two and a half gig. They typically use two pairs. To get to 10 gig, we have to use all four pairs. And there's even a type of Ethernet called single pair Ethernet. If you're thinking it only uses one pair, ding ding ding ding ding ding. Winner winner, chicken dinner, you got it. It only uses one pair. So let's first talk, you know, EMI for as far as cabling comes in two types. Internal interference and external interference. Internal interference is going to be near-end crosstalk, far-end crosstalk, power sum near-end crosstalk, power sum foreign crosstalk. The external interferences are going to be like alien crosstalk. Now, those names just tell you whether the inf the interference is happening either inside or outside of the cable. Internal interference all happens inside the cable. External interference starts on the outside and works its way into the cable. That's the difference between those two. First,

Termination Habits That Break Performance

11:49

let's talk about near-end crosstalk. Near-and-crosstalk is how much one pair interferes with another pair at the near end of the cable. So you got four pairs. So for example, it would be the blue and the orange interfering with each other at the near end of the cable. Far end crosstalk is how much one pair would interfere with another pair at the far end of the cable. And then power sum near end crosstalk is how much those three pair interfere with that last remaining pair at either the near end or the far end. The near end would be power sum near end crosstalk, the far end would be called power sum far end crosstalk. So let's talk about what are some of the common problems, common things that cause near and crosstalk. Untwisting the pairs too much. We all have seen it. You know, you're allowed to untwist up to half of an inch for cat 5e and cat six. Some people even tell you a quarter of an inch. And that pair on twist is measured from where the pairs exit out of the jacket to where they terminate. Now, when you go to terminate a jack, you're not going to just strip off a quarter inch of that jacket off. You're going to strip off an inch and a half or two inches. But when you lay them in the jack, make sure that the back side of the of the jacket comes all the way up to the connector. If you do that, you're going to be well within that half inch. You see, those twist pairs, they aren't there by accident. In fact, if you look at a cat 5e, a cat 6 and a cat 6a, you will notice, you will notice that they're all twisted at different rates. And they're twisted at different rates because the cable is performing at different frequencies for each of those cables. For example, cat5e operates at 100 megahertz. Cat 6 performs up to 250 MHz. Cat 6 performs with the 500. Cat 8 performs with the 2G. Now, because we're operating at those higher frequencies, we have to increase the twist rates to reduce the effects of VMI out of the out of that cable so it still continues to work. When you remove the twists, you're removing the protection. It's literally that simple. And when you untwist too much door and determination, what's going to happen is you're going to start getting marginal fails or complete outright fails. A marginal fail is a test result that says either star pass or star fail. It is so close, the test results are so close, the tester doesn't know if it's barely a pass or barely a fail. And a lot of manufacturers don't accept marginal test results. They're going to make you go back and re terminate and retest. And most of the time, when you have problems with near-end crosstalk, far-and crosstalk, and the power sum crosstalks, those are almost always, but not every time. The majority of the time, those are almost going to be because something that you did wrong. You untwisted too much of the pair. You didn't lay the cables in correctly. When you actually look at a cable, the test results of a cable, you'll notice there's an overall physical length of the cable, and let's say, for example, 150 feet. But when you actually go inside and look at the test results, you will notice that the pairs are all different lengths. One pair might be 150 feet, the second pair might be 151, the third might be 152, and the last one might be 153 feet. And the reason for this difference in the twists is the amount of twists in the pair. The more twists, the more protection. The higher the frequency, the more protection is needed in that cable. In fact, in some Cat 6A cables, the difference between the shortest pair and the longest pair at the full length of the cable, 90 90 meters, 295 feet, the difference between the shortest pair and the longest pair, I have seen it sometimes as up to almost 10 feet of difference between those. That's ridiculous when you think about that.

Alien Crosstalk And Cable Combing Fight

15:48

But let's not forget about alien crosstalk. When I say alien crosstalk, I don't mean aliens are coming down from space interfering with your cable. Alien crosstalk is defined as how much one cable interferes with another cable as it's going down the cable pathway. Not the pairs inside the cable. This is how much one cable interferes with another cable. And this became a huge issue when we started coming out with 10 gigabit Ethernet. Because to get to 10 gigabit Ethernet, again, we're using higher frequencies, Cat 6A, 500 megahertz, and we're using all four pairs. So there's a lot more potential for EMI. So what you have is you have one cable interfering with another cable in the cable pathway. Now when Cat 6A first came out, it was a common uh a common recommendation by most manufacturers to quit cable combing cables. Cable combing is when you take a when you take a cable it's not a very good example. When you take some cables and you comb them in nice and pretty. So when 10 gig first came out, they started recommending no longer cable comb to randomize the cables in the trays. Just lay them lay there loosely. So that way no two interfere with each other. Manufacturers, though, have gotten around ways to fix the cables so you can cable comb them again. That's going to be a huge argument in our industry to cable comb or not the cable comb. Hey, in the in the chat box down below, tell me, do you prefer to cable comb or do you prefer to randomize? Some cable companies like the cable comb. They like to have the higher quality product. Yes, it takes more time. Yes, it takes more effort, and yes, it's harder to add cables to the bundles. But customers associate quality with their eyes. And when they go in and they see that cable comb all nice and neat and dressed all the way to the rack, they're going to assume that everything outside the telecom room was done correctly. So manufacturers have redesigned cabling. That's why Cat 68 cables got bigger than they were originally. They started putting crossweb separators or splines inside of them. And what that crossweb separator or spline does is it keeps those pairs further apart so that they don't interfere with each other inside that cable. You've got to be super careful though, because there's still old information out there on the internet. Now there's there's there's some uh a frequently asked question section on a major testing manufacturer's platform which says randomization is the way you should go. But that article was published nine years ago. Nine years ago, and our industry is an eternity. It's a long time ago. Manufacturers have long since figured out how to manufacture cables, cat 68 cables, so they're a little bit more resilient. But there are still some things you need to pay attention about cat 68 cables. Number one, they're gonna be larger. So, for example, a cat5e cable tip the OD typically ranges between 0.17 and 0.22. Okay, that's the outside diameter. Cat 6A cables can be anywhere from 0.233 up to 0.340. So they're going to be bigger. They're gonna be bigger for several reasons. They might have that crossweb separator inside of them. Cat 6A cables generally have 23 gauge conductors, which are bigger conductors than what's found in the Cat5E. Most Cat5E cables are 24 gauge. Now there are some larger Cat5E cables for PoE stuff, but the vast majority of Cat5E is going to be 24 gauge. And if you remember anything from your classes, the American wire gauge, the smaller the number, the bigger the conductor. The bigger the number, the smaller the conductor. It's an inverse relationship. And if you think you know why those numbers are backwards like that, tell me in the comments below. Let's see how smart my audience is. I bet you my audience will know. So

Separation Grounding And Pathway Rules

19:52

now that you have the background information, now let's understand the problem. Let's talk about the solutions. The good news is that most EMI, most crosstalk issues, can be prevented and they can be fixed. The first rule is pretty simple. Respect separation distances. Make sure that you know how far apart you need to stay away from electrical. If you're running next to near electrical in the ceiling, maintain at least 12 inches of separation from all electrical cabling. If you have to cross electrical, cross it at a 90. And power and data cables should not occupy the same space unless they've been specifically designed to do so. For example, like power poles. Sometimes you'll find power poles with a metal channel between the two, and you can put electric on one side and communications or low voltage on the other side. And quite often, most manufacturers will tell you that that power pole has to be bonded to a ground. Other good resources follow the NEC, the Nash Electrical Code, follow the TIA standards, follow the best practice manuals set out there by Bixie, the TDMM, and the ITSA manuals, and the pocket field guides. They have all kinds of suggestions in there for separation distances. Because most EMI problems start because somebody ignored those separation requirements. And that's usually when most problems happen, isn't it? When somebody ignores something. The second rule is to maintain the pair twist, as I mentioned earlier. When terminating cables, preserve that pair twist as much as you can to the point of termination. That's the best thing to do. Those twists are the are those twists are the primary defenses against interference. The more you untwist, the more problems you're going to have with interference. The third rule is pathway management. Avoid overfilling conduits. You know, there's a couple ratios out there. You know, the the NEC, this is why I said the NEC earlier. The NEC says that if you have three or more cables, the maximum fill ratio is 40%. Again, that's a conduit fill ratio number, not a firestop fill ratio number. We'll talk about fire stopping maybe in a different episode later on. But if you go by the Bixie TDMM, it actually will tell you 30%'s going to be better because it gives room for growth. And when you're factoring out your bend radiuses, you also got to factor in how many bends are in that run. For every bend, every 90-degree bend, you have to reduce the capacity even more so that way when you pull the cables through the conduit, it's not hard on the cables and it doesn't change twist rates because you're pulling on it hard and it doesn't break conductors. Oh, by the way, if you're putting cable into conduits, make sure you use pulling lubricants specifically designed for cabling. Okay. Do not use soap from the bathroom. Okay, that soap has not been tested against the long-term effects of what happens to the cable jacket when it gets exposed to it. Use polywater or clear glider, some other tests, some other cable lubricant that has been tested and certified to make sure that you be used with low voltage cabling. Avoid overstuffing cable trays. This is where a lot of people don't pay attention. Because when you think about cable trays, you got the rungs that you're running your cables across. In fact, you should not stack the cable more than six inches high when running down a cable tray. Because when you run over those rungs, if you've got cables stacked higher than six inches, you're putting a lot of weight on those cables on the bottom, which are transversing across the rungs, and it could deform the jacket. In fact, that's the key. You want to make sure that that cable jacket is the way it was from the factory. If it's crushing the jacket, if it's kinking the jacket, if it's leaving little white hash marks on the jacket because you've done something to it, you've bent it too far. That is going to affect the performance of the cable plant. Another good tip is to use Velcro instead of tie wraps. Velcro is re-enable. It's almost impossible to over cinch with Velcro. You can use tie wraps according to the standards, but if you do use tie wraps, they should be loose so you can spin them on the bundle, and they should be so loose that they don't deform the cable jacket. Also, if you do put in tie wraps, cut them flush. The next tech will appreciate you doing that. Oh and by the way, I forgot to tell you, those tie wraps should be placed at irregular distances. So in essence, what you really want to do is you want to make sure that you maintain that cable geometry. You want to make sure when the cable is installed that it looks exactly like it did when it came off the manufacturing plant at the factory. The fourth rule is proper bonding and grounding. You know, especially in environments where you might have industrial environments, where you might have high voltage. A properly bonded infrastructure is going to help manage that electrical energy and can reduce the interference problems. A shielded cable plant bonded correctly will provide you the best type of protection out there. But a shielded cable plant that hasn't been bonded to a ground correctly will act worse than a UTP solution will. So make sure you follow your manufacturer's instructions when it comes to installing shielded cable plants. The majority of the time it's going to tell you to bond the shielded patch panel in the telecom room, and then at the work area outlet at the faceplate side, you should be using shielded patch cords. That shielded patch cord attaches to the chassis on the PC and it picks up its ground through the third prong in the electrical outlet. If you don't have both sides bonded to the ground, you basically just have an antenna. And somebody who's studying for their ham license, antennas are good for ham radio, but they're not good for communications cabling. The fifth rule is to pay attention to the bundling. Now we've talked about how to dress cables, but let's talk about PoE, power over Ethernet. Power over Ethernet's available in a bunch of different sizes. It can be also up to 90 watts. 90 watts. That's a lot of cable. Now there is some information in the NEC that tells you how many cables you can have in a bundle and be compliant with the code book. If you want to go look it up, it's table 725.144. But don't use it. I highly recommend you go by the Bixie standard, which says 24 cables or less. That's going to guarantee that that interference or the PoE from all that electric from that DC current is not going to overheat the bundles. Okay. DC current, here's why we have PoE over cable and not have any interference, because it's done with DC current, not AC current. DC current doesn't have a sine wave associated to it, but it will generate heat. So larger bundles will generate heat. And if you remember anything from uh from a beginner's class, cables, when they get hot, they lose more signal. They attenuate. And that's something you definitely don't want to happen on the cable. That's why the manufacturers always test their cables in certain temperature ranges to simulate what they're going to be done, how they're going to be installed in the field. And finally, always evaluate the environment before you actually install the cable. Make sure you know where is the electrical room? Where is any potential transformers on this floor? Is it on the other side of the wall? If it's an industrial plant, are there any large motors or generators? Think about any potential sources of EMI. Again, flesh and light fixtures in your old office buildings. Oh, if you haven't thought about yet, neon lights. Neon lights generate a ton of EMI. Had to deal with that in the podcast studio. Because the best technicians aren't just cable pullers, they're observers. Right? They look at the environment. They look around, they pay attention to everything. They look at the entire environment and they identify potential problems before the first cable's ever installed. And that's what separates a good technician from a great technician. And I

Wrap Up And Listener Challenge

27:57

know by you listening to this podcast, you want to be one of the great technicians. So in closing, you know, EMI and Crosstalk, they remind us that successful network installations aren't just about connecting point A to point B, connecting the server to the computer. They're about understanding everything happening around that cable. The best technician understands that the cable is only part of the system, the environment matters as well too. And installation practices matter, pathways matter, terminations matter. And if you understand EMI, near and crosstalk, far and crosstalk, and alien crosstalk, you're no longer just installing cable. You are engineering performance. And that's what customers are really paying for. They're not paying for the cable, they're not paying for the connectors, they're paying for performance. I'd love to hear from you in the comments below what's the worst EMI or crosstalk issue that you've ever encountered in a project. Drop your story in the comments below. I hope you found value in today's episode, and make sure you subscribe and hit that notification bell. Until next time, knowledge is power.