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Guest

Hi,

I'm having a CAT5 network cabling issue and am fresh out of
troubleshooting ideas. The cable is a CAT5 stranded cable, which I
made to be about 100 feet long. Each end uses an RJ-45 connector and I
made the cable a crossover cable to connect two NICs directly (pins 1-3
and 2-6 were switched on one end). Due to the application
requirements, at one of the ends I have another 3 feet of 8-wire cable
inserted, which has a slightly larger gauge. To interconnect these 3
pieces of cable, I have an 18-22 AWG butted crimp terminal on each
individual wire.

Here's the problem: When I plug my network cable between two machines
(or a hub and one of the machines), I get a link light and activity,
but cannot get an IMCP ping response nor can I get get a response via
SSH. I have no problems when I use a similar CAT5 crossover cable that
is only 3 feet long. According to the hub, I have activity on the
port, but I haven't been successful in communicating over the 100'
cable.

I've verified the continuity between the two ends several times. I
made sure each pin has only one solid connection on the opposite end,
which match the pinouts for a crossover cable. Assuming that my cable
really is a crossover cable and I didn't make any mistakes verifying
this, how should I continue troubleshooting this problem?

There are 2 different reasons I can think of that may be causing the
problems. The first is that even though CAT5 is specified to work up
to 100 meters (about 300+ feet), maybe my signal is losing it's
integrity due to the length of the cable (this is definately a long
transmission line) and the connectors I had to insert near one of the
ends. The second theory is that since my cable is coiled up on a desk
and the fact that I have a long transmission line, my signal is losing
its integrity due to crosstalk noise from the signal's delayed version
of itself.

The first hypothesis could be solved by using a router, or something
that will boost the signal assuming this is purely a length issue. If
the connectors are causing transmission line problems, I don't know
what options I have, other than replacing the butting connectors with
something smaller (but I can't get around inserting the 3' cable at one
end). The second possibility would not be an issue once I unravel the
cable, but I doubt this will work.

When I attempt to troubleshoot this problem tomorrow, what else should
I try? Anyone have any experience with this?

Thanks very much for your help!

Jason

Guest

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.

Dale Farmer · Guest

gaudetteje@gmail.com wrote:

Stuart Robinson · Guest

Guest

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

Guest

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.

Dale Farmer · Guest

gaudetteje@gmail.com wrote:

James Knott · Guest

gaudetteje@gmail.com wrote:

Guest

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):
http://www.subconn.com/subconn.asp?page=cir15&pic=img2f

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.

Perkowski · Guest

gaudetteje@gmail.com wrote:

Guest

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

James Knott · Guest

gaudetteje@gmail.com wrote:

James Knott · Guest

gaudetteje@gmail.com wrote:

Guest

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.

James Knott · Guest

gaudetteje@gmail.com wrote:

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