Troubleshooting a 100' CAT5 cable - need assistance

Since this may be part of the problem, I should explicitly indicate how my cables were inserted into each RJ-45 jack.

Pin Jack A Jack B

1 w/o w/bl 2 o g 3 w/bl w/o 4 bl bl 5 w/g w/g 6 g o 7 w/br w/br 8 br br

I'm assuming these may not match the specifications and thus I don't have proper shielding from the twisted pair. I also still suspect the crimp connectors may be causing unwanted reflections in the network traffic.

Its probably all of the problem, to be honest I am extremely surprised it worked at 30M (before you added the extra bit)

You have a split pair on the active lines, there should be one pair on 1,2 and another pair on 3,6. You need to wire it thus;

1 w/o w/g 2 o g 3 w/g w/o 4 bl br 5 w/bl w/br 6 g o 7 w/br w/bl 8 br b

Although for 10 and 100Mbs ethernet there is no need to wire up or swap the 4,5 and 7,8 pairs.

Stuart.

That is likely your problem. The inch or so of not twisted pairs will give you all sorts of problems. Crimp some 8posiiton modulars onto those ends, and then put a cat-5 f/f coupler there to give you your connectivity.

--Dale

Thanks for your help, Stuart. I've rewired my two end plugs to match the T-568A and T-568B standards on each end as you outlined. After checking the continuity between all pins, it still doesn't work. This time, however, I don't have a link light at all.

I'm going to split my completed cable into 2 parts. The first part will just be CAT5 twisted pair at about 30m and the second will be the

2 feet of untwisted large-gauge wire with crimp connections to CAT5 cable on either side. I'd expect to see that one works fine and the other does not to help me troubleshoot.

Jason

After splitting the cable into two separate sections with RJ-45 plugs on all ends, I've determined that the 30m cable works fine; however, the 3' untwisted cable with crimp connectors does not give me a link light when I plug any NIC or hub into either end. Again, I've checked the continuity of all possible wire combinations and verified my wiring is correct for a standard crossover cable.

I'm going to Home Depot or Radio Shack down the road to see if I can get some different 8-pin modular connectors rather than these individual wire butted crimp connectors. Either my problem is the 2 of

3 feet of untwisted pair wire, as Dale pointed out, or it's the connectors causing the issues.

Thanks guys. If you have any further thoughts, please let me know!

Jason

I was incorrect when I said the cable was stranded... My 30m or so of cat5 cable is actually solid. It is the 2 feet of untwisted cable that is stranded.

James: The application that requires me to do this is to have a water-proof connector to the hull of a submersible vehicle. Rather odd application, I admit... However, the ethernet connection is necessary for controlling the vehicle at this stage. The waterproof 8-pin connector I have to work with is by Subconn.

The specific model I am using is the Micro 8 (MCBH8F & MCIL8M):

I understand that the cable is non-spec for ethernet communications, but I don't really have an option at this point. Is this strictly a noise issue? Should I try minimizing the noise from the connectors by replacing them with a solder connection? I can also reduce the size of the cable as a last resort; however, once I cut the cable I don't have a backup.

That's the problem. The waterproof part isn't just 3 feet, it's about

40-50 depending on how deep the vehicle will go. The cable from Subconn only extends 3 feet and I am waterproofing the connection to the CAT5 cable.

If I can't reduce the noise in the waterproof cable we have, then this would be our only other option, though _no_ water is acceptable as we will most undoubtedly fry the equipment if the power shorts in certain places. We have lots of gunk to plug up the hole as long as we can keep tension off of it.

As with any project, of course it needs to be working by tomorrow morning so switching to fiber isn't an option (yet). I will keep that in mind for later on if we still have the need to be tethered. Accoustic communications has been done many times before, but we don't have the equipment now.

I'd strongly suspect that the other cable you're using and the crimp terminals are causing the problems. They're way out of spec for ethernet. You need cat 5 or 6 cable and appropriate RJ45 connectors only. Anything else will cause problems, as you've discovered. What sort of application requires you to do that?

You're totally non spec. Read up on EIA/TIA 568 A & B. Choose one and wire according to spec, using the proper materials.

Also, you shouldnt be using stranded cable for home runs. You should only be using stranded cable for patch cords.

Stranded cat 5 has higher noise levels than solid core cable. You very well may get a link light but youll be hard pressed to pass data at 100 feet or more.

My two 2 cents....

Of course not. Flat silver satin does not provide the necessary pairing (twist) for noise isolation.

I have made flat cable work for 15m at 10baseT by using USOC order to give a small measure of noise (crosstalk) isolation. But I don't believe such tricks work for more than inches of 100baseTX.

If you cannot replace the cable by some twisted Cat5e because of your water"proof" connectors, you might try re-allocating conductors (breakout boxes/custom cables).

This project is worth real money, and it is probably for getting a Pentascanner or equivalent certification tool in to check your links. You won't make spec, but at least you wioll get an idea of what is "least bad".

-- Robert

Since you're only talking about 3 feet, why not extend the waterproof compartment to the surface, rather than using a waterproof connector? Use a sufficiently long piece of conduit or tubing, to reach a point above the surface, run the proper ethernet cable and then seal the top end, to keep water out. Ethernet is very fussy about meeting specs and your solution breaks enough things, to keep the circuit from working.

Agreed.

Stuart.

Can you do it, without a connector on the outside? Why not run the cat 5 directly into the devices, through a sealed access?

You're going to have to find some other way, as I doubt what you've proposed is workable.

I don't know of any watertight cat 5 connectors, but I haven't gone shopping for any either. There are pressure rated optical fiber bulkhead connectors out there, which would give you something that is good down quite deep. The optical fiber is also good for much longer lengths than the cat 5 cable. If you are just doing shallow water testing right now, you could run the intact cat-5 cable through a gland, and just accept a certain amount of leakage as a temporary inconvienece. You could also convert it to rs-485, which is much more tolerant of connector discontinuities.

--Dale

Sealing around the cable isn't going to be your leakage problem. The jacket of the cable isn't intended for watertightness, just for physical protection. Something you could try is to take a section of cat 5 cable, carefully strip away the outer jacket from a section, and then you have the four individual twisted pairs accessible to be packed into a sealing gland. Then terminate outside the pressure hull with a regular ( corrosion resistant! ) modular plug, which you can then plug in a regular cat 5 cable. Put that whole jack and plug into a pressure compensated oil bath to keep the water out of the connector.

I'd push hard for going to optical fibers. They are way more durable in a water environment.

--Dale

I found that the untwisted cable actually works with the 30m of UTP after many revisions. What I had to do was twist the individual wires coming in from the bulkhead, which consisted of about 1 foot of the 3. I also had to remove all of the butted crimp connectors, since the impedance changes must have been causing severe reflections to distort the signal. Instead, I simply soldered the pins together where they meet. I'm also going to try using some header and socket pins that can mate together. Those hopefully won't add much noise, but will be stronger than solder links.

Thanks for everyone's help, it definately helped me to get this working.

Jason

Your color coding to pins is incorrect and inconsistant....follow the information in this link for the proper sequence to use with either

10BaseT or 100BaseT ethernet

Due to the 3' un paired cable you may not achieve 100BaseT but you should be able to squeeze out 10BaseT

Joe Golan, RCDD

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