[Coco] [off-topic] cabling problems

[gene heskett]

On Tuesday, April 17, 2012 10:13:22 AM Paulo Lindoso did opine:

> Hi List,
> 
> It's completely off-topic, but since it seems there are a few Electronic
> Engineers in the list, I hope you can shed some light here...
> 
> I have installed a Cat6 cable between two extremes at my place to build
> a network bridge.  The cable extends itself for about 60m (that 180ft
> roughly), which means it's  well within Ethernet parameters (100m,
> right?)...
> 
> The problem is: when tested with a standard wire tester (for electrical
> connectivity), it passes; when you hook it to a router on one end and a
> computer on the other, it doesn't work. It doesn't pick up an IP address
> through DHCP and even if I force an IP within the network range, traffic
> doesn't flow.  On my Mac, it shows it is "Connected", but nothing
> happens...
> 
> I have changed plugs (cut the ends, re-wired with new RJ45), router and
> tested with a different computer to no avail... so I am really at a
> loss, here...
> 
> Can any of the EEs in the "house" shed me some light or give me any
> hint? Is there any other Ethernet limitation I am not aware?
> 
> Thanks for any help!
> 
> Paulo

There are 2 common pinouts used by cat5/cat6 cables, so you may want to 
write notes and compare the ends.

Wall plate type jacks are pretty large impedance bumps, both the crimp on 
connector, and the jack should be wired with the absolute minimum distance 
between the cables internal lay and its actual connection at the jack or 
plug.

There is a cable end that the wires can be inserted clear through which 
encourages the wires insertion to the minimum distance to the cable lay, 
and also allows a good look at the wiring order to verify it is correct 
before the crimping tool makes it permanent, and because the wire can be 
inserted till the connector is up against the cable lay. When the crimp is 
done, trim the ends off flush with the connectors plastic with a _sharp_ 
razor blade.  That connector is the best invention since sliced bread IMO.

They are unreal expensive, but there are testers available that can measure 
your cable and tell you within a few inches of where any faults are.  
Because they are in fact, specialized Time Domain Reflectometers, they tend 
to run well north of $1500, so even the pro's won't often have one of 
those.

There are also cheap ones (<$100) that only tell you if the right wire is 
wired to the right pin.  I think that is what Jim has used at the tv 
station, where at last count we had 3 separate network setups, with the 
last one running at 10Gb, but at about 75' max distances between the rack 
room & the 2 control rooms.  We also have several thousand feet of cable in 
the other two nets running at one gigabaud.  One is available at 
www.wdtv.com, the other is internal because we ran out of external 
addresses, but NAT & firewall bridged so everyone can surf while remaining 
invisible.  A router running dd-wrt or open-wrt for its NAT and firewall is 
quite often your best friend. I'm using a Buffalo Hi-Pwr as the main one 
here.  Both it, and the netgear something or other 614 I use in the shop 
support the best current wireless security, and with my pass-phrase will 
take a hacker a major part of the rest of the universe running down time to 
break.

The 100Mb stuff is much less critical, and I have 2 hunks of it suspended 
between the house & the shop building, and from the shop back to the garage 
so I have a net connection there while working on a computer.  Been 
swinging in the wind for about 10 years now, and the one coming back across 
the yard from the shop to the garage is 3+ years old.  With a router in the 
shop serving as a hub because there are 3 computers in the shop, one of 
them wireless, plus the cable back to the garage, and I still get my 385k 
bandwidth in the garage.  Even I can't believe it still works because both 
of those long pieces of cable are smashed flat for several inches getting 
from point A to point B & back to point C.  And I mean flat, as in about 
1/16" thick!  Both of those runs survived a 112 mph recorded blow back in 
2010 that took the roof off the house, and 3 of our 5 mature trees down, 
breaking them off about 7 feet up.  But the cat5 survived.  Go figure...

Cheers, Gene
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