Question RJ45 plug/Cable Tester Pecuilarity

Mantrid-Drone

Senior member
Mar 15, 2014
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I've been making my own custom length Ethernet/CAT cables for some time, braiding them etc.

I've been using a RJ45 cable tester like the one in this YT video to test them after crimping. It has been reliable in identifying problems when my work has not been up to standard :-


Its always bothered me that the tester includes a G: Ground testing LED window but no cable/RJ45 plugs I've used ie. even those with metal shielding which is supposed ground the cable too has ever made it light up.

The guy in the YT video mentions the ground (G) thing himself at 4' 45", saying it is for grounded cables so won't light up for typical home network cabling.

Well there is actually another reason why it doesn't light up. I took my tester apart earlier today wondering if I should buy a new one as I'd always assumed it was partially faulty. It is not.

If my version is typical the problem is that the tester and the remote only have 8 LEDS. There is no LED for ground (G).

So why is that window there?

More pertinently why are there tester PCB mountings for a 9th and 10th LED and on remote's PCB for a 9th LED?

The mountings are blanked with solder; I've tested the continuity and they are connected. The 9th ones are for the shield/grounding. The 10th pair on the tester's PCB route to the device's only IC (MC14017BCP) for who knows what intended purpose?

But the question is why do these testers omit the ground (G) LED? Just for the cost of fitting an additional single green LED?

Is there any reason why I cannot or should not solder in an additional pair of green LEDs myself and effectively reinstate the ground test function capabilities of the tester?

Finally I have to mention that on looking at the PCBs under a magnifier I was not impressed to find multiple solder splashes in two places which clearly bridged several traces. There were also indications of what looked like battery leakage residue. But that was nowhere near the battery compartment. The remote also had something similar and that does not have a battery.

Initially I assumed both these things were the cause of the problem and cleaned it all with a bit of gentle persuasion and some isopropyl alcohol.

It was only afterwards that I realisied there were only 8 LED and the device was actually functioning correctly despite this manufacturing sloppiness.
 
Last edited:

JackMDS

Elite Member
Super Moderator
Oct 25, 1999
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CAT type Network cable has no ground in the active RG network leads.

The ground in the shielded cable is external it is not part of the RG plug.


If the G on your tester is a problem get another tester without a G.

Or a real calss A+ Tester - https://www.grainger.com/product/2HTK2?ef_id=Cj0KCQiA5OuNBhCRARIsACgaiqVQ_C3vD-vqih36kZg3uiylIVsI7JiYBjf_WrEC9Wpfpac43lx-_a4aAjf2EALw_wcB:G:s&s_kwcid=AL!2966!3!496359971011!!!g!470148536830!&gucid=N:N:PS:Paid:GGL:CSM-2295:4P7A1P:20501231&gclid=Cj0KCQiA5OuNBhCRARIsACgaiqVQ_C3vD-vqih36kZg3uiylIVsI7JiYBjf_WrEC9Wpfpac43lx-_a4aAjf2EALw_wcB&gclsrc=aw.ds


:cool:
 
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Mantrid-Drone

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Mar 15, 2014
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Of course I know its not part of the actual plug connections but surely the continuity of the shielding is important.

If you buy off the shelf cables with plug shielding there is continuity so the shielding is all interconnected. According to both RJ45 and RJ11 connector specs, when used, the shielding is there for panel grounding. You seem to be saying it is unnecessary; so why are they manufactured like that if that is so?

As asked, whether it is important or not, why does the tester have a LED window for ground (G) testing but no LED. As described the mounting connections are there on the PCB, they work* but are blanked off.

If you haven't stripped back the cable's shielding so it makes good contact with the metal plug shielding you might not have continuity which is what the tool is there to test all the connections for.

* there is continuity and a voltage but...........................I've rechecked and its less that than the other LED connections which are all around 2v. So whether it will work if a LED is 'reinstated' to the provided PCB connection I'm now not sure.
 
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DaaQ

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Dec 8, 2018
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Not sure if related, but I have used CAT6 shielded cable that had an external copper ground wire. Presumably to bond it to the main power ground. For like Outdoor POE devices.
 

Hans Gruber

Golden Member
Dec 23, 2006
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There is no reason why a cable has a ground or not. Typically if you get a Cat6a cable with a metal jacket around the RJ45 connector, it's grounded. But not always. If you have a stiff cable with the metal jacket housing around the RJ45 connector, it's grounded.
 

DaaQ

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Dec 8, 2018
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There is no reason why a cable has a ground or not. Typically if you get a Cat6a cable with a metal jacket around the RJ45 connector, it's grounded. But not always. If you have a stiff cable with the metal jacket housing around the RJ45 connector, it's grounded.
And if you do not have metal jacket housing connectors?? Shall I get a piece and upload the picture for you? This is outdoor environments I am referring to. Point to Point Antennas.
 

Hans Gruber

Golden Member
Dec 23, 2006
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And if you do not have metal jacket housing connectors?? Shall I get a piece and upload the picture for you? This is outdoor environments I am referring to. Point to Point Antennas.
Technically I think you have to have the metal jacket to make the ground possible. If it doesn't have a metal jacket around the RJ45 housing, grounding would not be possible. A shielded cable has metallic foil surrounding the wires. That is why the cables are stiff. If you do not have a metal housing around the plug, I don't think it's possible to be grounded. I think the reason for grounded/shielded ethernet is to avoid ground loop or electrical interference around highly sensitive equipment.

If you have POE devices, shielded cables would probably provide better power to a POE switch/device.
 

JackMDS

Elite Member
Super Moderator
Oct 25, 1999
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In general Grounding of Network cables belong to two purposes.

Grounding to avoid damage from strong signal source. Like t cable hit by lighting or similar electrical "Noise"

In such cases it must be well ground in few spots to ensure shortening the signals to the ground (including Ground Ro

Otherwise the issues involve screening the Ethernet wires from getting emission of low signal that increases the noise in the wires and creates low Signal to Noise Ratio that decrease the "speed" the Network Ethernet signal.

To avoid the latter a screened cables can be used and they had to be grounded only on side of panel.

For special occasions this aspect has to be planned ahead and special cables and connectors have to be purchased.

Here is an example for Shielded CAT6 connectors.


Cables - https://www.amazon.com/InstallerParts-Ethernet-Cable-Shielded-Booted/dp/B06Y4DKPCJ/


:cool:
 

DaaQ

Senior member
Dec 8, 2018
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For the sake of argument. Here is the pictures of the stuff I have. I accidentally pulled the whole twisted pair out because it was a short piece.
IMG_20211221_233649131.jpg
 

DaaQ

Senior member
Dec 8, 2018
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And the box.

Sorry last photo was too large and had to do them each separate.

I think not grounding my edge router is what took it out during last storms power outage. Meh.


IMG_20211221_233736881~2.jpg
 

Hans Gruber

Golden Member
Dec 23, 2006
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You have shielded solid ethernet cable with a ground wire. If you are going to terminate and ground to a RJ45 tips. You want the metal clip RJ45 connectors. Then you have to correctly ground each end of the ethernet cable to the metal RJ45 connectors. I was under the impression that you had pre-made ethernet cables. Since the cable is solid, it will be less flexible than stranded cable.
 

Fallen Kell

Diamond Member
Oct 9, 1999
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You have shielded solid ethernet cable with a ground wire. If you are going to terminate and ground to a RJ45 tips. You want the metal clip RJ45 connectors. Then you have to correctly ground each end of the ethernet cable to the metal RJ45 connectors. I was under the impression that you had pre-made ethernet cables. Since the cable is solid, it will be less flexible than stranded cable.
Hans is correct. The last part is actually important. This isn't designed for use as a patch cable, but for in-wall/in-conduit applications where the cable will not be subject to moving. The solid conductors do a better job transmitting signals, but make the cable stiffer and subject to stress breakage (for example: take a paper clip and bend it back and forth a couple times and you will see that it snaps at the bend point. The same will happen to the wires in a solid core cable. Again, not an issue for something that is installed in the wall or in conduit and as such, isn't moving/flexing, but is a problem if it connected to camera that is on a motorized swivel that sweeps back and forth.).
 
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Fallen Kell

Diamond Member
Oct 9, 1999
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A braided copper (BC) drain wire is normally just for grounded shielding purposes. The braids make is more likely to be in contact with the metal foil (or copper mesh) shielding and is typically designed to be attached to the metal housing on a shielded RJ45 connector.
 

Mantrid-Drone

Senior member
Mar 15, 2014
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Back a bit more on topic, although the wider discussion has been interesting and useful, I have detemined that the GND test non-option LED can not simply be reinstated with this type/make/design of tester.

I guess the IC that controls the test sequence is set to cycle through just the main 8 connections. So whilst the '9th' PCB LED mounting position does have continuity it simply does not have enough voltage to light a LED at any point.

It could probably be wired up directly from the shield/GND PCB connections with power bled off the 9v battery. That would need a resistor to be fitted and, of course, the LED would be permanently lit, assuming the shield/GND wiring of the cable was OK.

Don't think it is really worth the bother TBH.
 
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