My latest motherboard has built in 1000baseT (gigabit ethernet over
twisted pair) and comes with a utility that tests cables.  It'll provide
minimal TDR capabilities - in addition to the usual shorts/opens, it'll
tell you where in the cable the short/open is, how long the cable is,
various parameters about the cable, improperly connected pairs.  Some
tests need a similar network card on the other end, but most run with
just one end connected to this board.

I'm hoping to find a PCI or PCMCIA card with this capability - it'll
save me tons of time!  What I'd /really/ like is a handheld driving one
of these cards.  It'd be neat to look at the chipset info and see if
it's interfaceable with a low level controller...

-Adam

Howard Winter wrote:

>Russell,
>
>On Mon, 29 Mar 2004 16:28:52 +1200, Russell McMahon wrote:
>
>
>
>>Best of all was including a short length of wrong impedance cable in a coaxial ethernet installation.Guess
>>
>>
>how I know :-(
>
>Ah, memories!  I remember getting a call from a secretary at our office, who said "Get here and fix this
>(expletive deleted) thing before I throw it out of the window!"
>
>Never being one to underestimate a threat like this, I headed back (from a client's) and found that
>Wordperfect would take 5 minutes to load, then another 5 to open a file, etc.  It was a network wide problem
>so I set to with the time-domain-reflectometer (praising the accounts department that I'd been allowed to buy
>one!) and it showed some odd readings - usually you open the termination at the one end end of the 10-base-2
>(50-ohm coax) and connect the TDR at the other end and it gives the length of cable to the open end of the
>network segment, then you work along and as you exclude a length of cable the remaining length shown reduces
>accordingly.  This didn't!  It intermitently showed a much shorter length, and it wasn't consistent from the
>two ends,  so I did a "binary chop" to locate where the problem was.  I found that someone had inserted a
>piece of coax they'd found in a cupboard, to add their machine to the network, and it was (I think) IBM
>terminal cable: 75-ohm instead of 50.  I replaced it with some of the right stuff, and harmomy was restored.
>I'd like to say that the secretary was eternally grateful and demonstrated it... but sadly not  :-(
>
>I'm rather glad that 10-base-T (twisted pair) caught on and replaced coax - it's much easier and more reliable
>to use all round.
>
>I wonder who got custody of the TDR?
>
>Cheers,
>
>Howard Winter
>St.Albans, England
>
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