Selecting the Correct Connector

Selecting the Correct Connector

Written by Don Schultz, Technical Expert, Fluke Networks Versiv & BICSI INSTC Certified Technician

All Ethernet cable must be terminated at both ends. One way is to use a RJ45 connector. For some great background information on what a RJ45 connector really is, and why the naming continues to be confusing, see What is an RJ45 Connector?

Selecting the correct connector for your Ethernet data cable is entirely dependent upon the type and construction of the cable to be run. Technically, Category has nothing to do with it. It is all about fitment.  Information is half the battle in the quest for success, and this can be a bit tricky. Let’s get fitted!

I am including a video with this blog to provide some hands-on examples in addition to the written portion. Both bring something to the table, and the video should be watched in conjunction with reading.

Do I need a shielded connector?

This is an easy one. If the cable is shielded, you will want to use shielded RJ45 connectors. Conversely, if the cable is unshielded, you will want to use unshielded RJ45 connectors. Using a shielded connector on an unshielded cable will yield no benefit, assuming the fitment is correct to begin with (and likely it won’t be). Shielded connectors are typically “up size” in nature, and usually won’t make proper electrical connections with thinner unshielded Ethernet cable conductors.

When it comes to unshielded connectors on shielded cable, don’t do it. Shielded cables need shielded connectors for the cable shield to function properly (called bonding). Again, this is assuming you can even fit an unshielded connector onto the shielded cable. Shielded cables are typically thick and have thick insulated conductors, so good luck jamming one on if you should try.

Shielded vs unshielded


Once you have decided on whether the RJ45 connector (also referred to as a plug) should be shielded or not, the next thing is…

Research for the right cable & plug

Any reputable manufacturer will have detailed specifications and publish them. Avoid any manufacturer that does not publish all of the required details as you will be playing a guessing game from the start. They are likely not a manufacturer, but simply a reseller that will offer little to no support for their products.

For the Ethernet cable you will need to know:

  • OD (outside diameter) of the Ethernet cable (the overall thickness). This is often expressed in millimeters (mm).
  • Conductor insulation diameter (the actual conductor wire plus insulation thickness) and likewise this measurement is often expressed in millimeters
  • If the cable has solid or stranded conductors
  • Pro tip:  Be aware of the potential tolerances (-/+) for the conductor insulation diameter

For the RJ45 connector you will need to know:

  • Cable jacket OD that the plug is capable of accepting
  • Conductor insulation diameter range that the plug is capable of accepting
  • If the plug is 2 prong or 3 prong. 3 prong plugs will work with stranded and solid copper conductors. 2 prong plugs work with stranded copper only.
  • Do not shop by Category for the RJ45 plug as this can be misleading when mixing components from different vendors
Cross-section of a typical Ethernet cable

Cross-section of a typical Ethernet cable

“Category” stated on any bag of RJ45 plugs can be misleading when it comes to proper fitment.  There is little, if any, correlation between the two.  trueCABLE is the exception here since we sell a system.  We go the extra mile of testing our components together.  So, a trueCABLE CatX unshielded RJ45 plug will fit and function on all of our unshielded CatX Ethernet (we will note exceptions as necessary).  We also thoroughly document our connecting hardware so you can make an informed choice if you are not using trueCABLE brand Ethernet cable.

Are you, the consumer, being lied to? Not precisely. When a manufacturer (that only makes plugs and not the cable, for example) states a category on their plug it’s because they assume the consumer is not technically savvy enough to choose based upon technical data. This is not only a bit insulting, it is confusing. A properly documented and advertised plug would be listed as “Unshielded RJ45 Plug, 3 prong for solid copper Ethernet cable, fits up to 7.00mm OD and 0.94 to 1.04mm insulated conductors.” So, what did the “XYZ Manufacturer” do? They advertised their plug as “Cat6”, leaving out all the important stuff, and this leaves you guessing.

trueCABLE does it differently...


Here’s the relevant data from one of our Ethernet cable specification sheets, specifically Cat6 Unshielded Riser:

Cat6 Unshielded Riser

So, for this cable we can see it has:

  • Solid copper conductors
  • Jacket OD of 5.90mm
  • Conductor insulation diameter of 0.96mm

Here’s the data for our Cat6/6A Unshielded Pass-Through Connectors:

Cat6/6A Unshielded Pass-Through Connectors

The dimensions from the connector specification sheet shows it works with:

  • Cable jackets OD up to 7.30mm
  • Insulated conductor diameters from 0.95 – 1.05mm
  • Solid or stranded copper conductors

We have a match!

Best Practices

  1. Staggered style plugs, all other things being equal, do perform somewhat better than eight across style plugs due to less crosstalk at the connector. This effect is most pronounced with high bandwidth Cat6A terminations. Both styles will pass Cat6A testing, but the stagger plug gives more “headroom”. If you seek the highest performing RJ45 connector to use with your Cat6A termination, then select the proper fitting staggered style. A great example is our Standard Cat6/6A RJ45 Unshielded Connectors. When testing with our Fluke DSX-8000, I can produce a 5.0 dB better NEXT parameter when using the stagger style standard plug as opposed to the eight across pass-through Cat6/6A style with trueCABLE Cat6A Unshielded Riser.  
  2. When buying cable and connectors from different vendors, try for the middle! For example, if your Ethernet cable has a stated insulated conductor diameter of 1.00mm, then select a RJ45 plug with an insulated conductor range of 0.95 to 1.05mm. This will give you the best fitment and performance and also allows for tolerance changes from lot to lot (which on Ethernet cable can vary as much as +/- .03mm).
  3. Cable strain relief boots are a useful addition! The weakest link in the system is always the termination. Strain relief boots take additional strain off of the termination contacts.   This helps to optimize electrical performance and serves as a reminder not to bend the cable too hard at the termination point, which can result in a poor performing connection.
  4. Buy more connectors than you need. It is wise to test terminate (crimp) the connectors onto the cable to make sure you can work with them. In addition, if you make a bad crimp then you can simply use any extras. Even the most experienced installers make a bad crimp from time to time.
  5. If you are new to this kind of activity, then practice as much as practical. The more terminations you make, the better you will get.

Did You Know?

For cable insertion into the back of the connector, connectors come in four primary types:

  • Standard (solid nose) non-stagger eight across
  • Standard (solid nose) load bar staggered (four high, four low)
  • Pass-through non-stagger eight across
  • Pass-through staggered (four high, four low)

  • Staggered style plugs are primarily designed to accommodate cable with thicker insulated conductors.  If lined up eight across, the conductors would exceed the external size of the RJ45 plug and thus need to be staggered.
  • There is nothing in the ANSI/TIA 568-2.D specification which dictates RJ45 plugs should be staggered for any particular Category, not even Cat8 
  • Some connectors lack a strain latch, and will require a crimp and termination tool that has an adjustable strain latch presser bar such as our All-In-One Crimp and Termination Tool. If not adjusted out of the way, the presser bar will destroy the rear of your RJ45 plug. This is often found with large shielded connectors that also have an external ground. The external ground tab serves as the strain relief in this case. The external ground tab must be firmly and properly crimped down in order to avoid electrical connection issues!
  • If you do make a bad termination, then the connector is trash and cannot be reused

So, now you know enough to select the proper RJ45 connector for your next Ethernet project. Practice makes perfect, so my sincere advice is to dive right in and start putting on connectors. You will likely make mistakes, but that is the best kind of learning.



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