Load Bar Staggered RJ45 Connectors: Do They Increase Ethernet Cable Performance?
Written by Don Schultz, trueCABLE Senior Technical Advisor, Fluke Networks Copper/Fiber CCTT, BICSI INST1, INSTC, INSTF Certified
Companies selling staggered RJ45 8P8C modular plugs often state in the product description that this new fangled attachment “improves cable crosstalk performance”. What exactly does this mean to you, and is it really true? Have companies embarked on another marketing scheme to fool you into buying the next greatest invention where the “older” product works just as well?
Spoiler alert: Yes, staggered RJ45 connectors can have a measurable effect on certain Categories of Ethernet cable in terms of crosstalk so nobody is being dishonest. The thing is, will you even notice? All other conditions being the same, no you won’t. Don’t get any illusions that your Internet speeds will greatly increase. Read more to find out why.
Pictures, just in case you were wondering what the difference is:
What is crosstalk again?
Crosstalk is the obnoxious phenomenon that naturally occurs with copper cabling when one wire, or pair of wires, is sharing a signal with another inside the same cable. Sharing, but not in a good way! Sometimes you will see this referred to as NEXT (Near End Crosstalk) or the old term FEXT (Far End Crosstalk which is now expressed as ACRF). If you see a statistic referring to this unwanted phenomenon, it will be expressed in dB (decibels).
A handy picture will help…
No matter how you refer to it, too much of it is bad. Since we don’t live in a perfect world, some crosstalk is expected and accounted for in the ANSI/TIA 568 2.D specification. Different Categories of Ethernet cable have different allowable levels of crosstalk. Not surprisingly, the higher you go up in Category the less you can have to still meet specifications.
Please note we are not talking about alien crosstalk. That is a different issue, which occurs from one cable to another. Read more in When Aliens Attack! Avoiding Ethernet Alien Crosstalk.
Ok, so we know too much crosstalk is a bad thing. When you have “low” crosstalk on an Ethernet cable run, it is known as higher headroom. High headroom means a greater ability to handle adverse conditions that might come up. An Ethernet cable run with more crosstalk and therefore less headroom is less desirable. A slightly out of specification bend or other wonky thing you did when installing your cable can decrease cable run headroom.
Think of it like this...in a test scenario allowable headroom receives an “A” and awesome headroom receives an “A+”. Therefore, higher headroom is a good thing, technically speaking.
That all said, can you overachieve and hit a point of diminishing returns? Well, it depends.
The Big Experiment
Me being me, I wanted to do an “apples to apples” comparison of “straight across” vs. “stagger load bar” RJ45 connectors. What I found was interesting.
- Fluke DSX-8000 Cable Analyzer
- Cat6A Unshielded (U/UTP) CMR cable
- Cat6 Unshielded (U/UTP) CMR cable
- Cat6/6A Pass-Through Unshielded RJ45 plugs (not staggered)
- Cat6/6A Standard Unshielded load bar RJ45 plugs (staggered, solid nose)
For both Cat6 and Cat6A cables the length was 295 feet, which is the maximum permitted for Modular Plug Terminated Link (MPTL). Quite simply, a permanent link is “jack to jack” or “rack to jack”. A MPTL link is “jack to plug”. MPTL links are commonly seen in use with WiFi access points and surveillance cameras, often with PoE.
I terminated one end of the cables to an unshielded keystone jack, using a Cat6 rated one for the Cat6 Riser and a Cat6A rated one for the Cat6A Riser. The other end was terminated to a RJ45 plug. Once I tested the cable, I cut off the RJ45 plug and terminated again with a different type and tested again. I kept all test conditions identical as much as possible. What we have below are the Fluke DSX-8000 test results.
First up is Cat6 U/UTP Riser:
Ok, we have 5.3 dB Headroom for the pass-through straight across style RJ45 on Cat6
Ok, so we didn’t see any real improvement with load bar staggered plugs on Cat6. Good to know. How about Cat6A U/UTP Riser where things get a lot more finicky?
Well, we have 2.8 dB Headroom. Not bad, and certainly a PASS with the pass-through style Cat6/6A straight across RJ45.
Well, now things are getting interesting. We see a full 5.0 dB improvement with the stagger load bar standard RJ45 plug.
When it comes to Cat6 Ethernet there is very little, if any, improvement with using stagger style RJ45 connectors. Things change with Cat6A, where we see a definite and measurable improvement in crosstalk performance. This is due to the higher operating frequency of Cat6A, which is set by ANSI/TIA 568 to 500 MHz. Staggering the conductors at the connector is keeping crosstalk down a bit more.
As it turns out, once you move past 350 MHz crosstalk starts showing up as a real problem. This is why the 250 MHz of Category 6 and paltry 100 MHz of Category 5e are not affected nearly as much (or at all) by switching out RJ45 connectors.
That all said, will it really matter in the field? That is up to you to decide. All full length cable runs in this experiment passed very strict ANSI/TIA 568 2.D MPTL testing regardless of the style (straight across vs. staggered). Even so, you really should shoot for the stars if it is not a big hassle.
Given the considerable 5.0 dB improvement seen on Cat6A, I would recommend you choose the stagger load bar style. Why?
- The stagger load bar style costs less than pass-through
- The stagger load bar style plugs have a bigger back end (where the cable jacket goes in) which makes it easier to insert the cable into the connector
- You still get backward fitment compatibility with trueCABLE U/UTP Cat6 of all types (indoor and outdoor)
- The stagger load bar style works with our really thick insulated conductor Cat6A U/UTP Plenum.
The only disadvantage to our Cat6/6A staggered load bar style RJ45 is the position sensitive load bar. You have to be aware of this idiosyncrasy and pay a little more attention to what you are doing. I explain a lot more in How To: Terminating a Cat6-6A Standard Load Bar Unshielded RJ45 Connector about working with this specific plug.
In the final analysis, it really comes down to preference since both work. Given a choice, I would go with the stagger load bar kind just to “be sure”. One never knows when Mr. Murphy will mess stuff up for you!
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