A TDR attenuation/NEXT (near end cross talk) test on a livingston
supplied cable gives the following results (CAT5 patch cord):
The only real difference I can see is only pairs 1-2 and 4-5 are
connected but,
Passive Hub SCR = 54.6 dB
Active Hub SCR = 55.0 dB
NEXT @ 19.7Mhz = 53.2dB, @10.1Mhz = 48.5dB, @ 5.1Mhz = 53.5dB , @
2.1Mhz = 60.0dB
Attenuation @ 16Mhz = 0.3dB, @10Mhz = 0.4dB, @ 5Mhz = 0.4dB, @ 2Mhz
0.0dB
So, basically a pretty good cable. In fact is seems to have it's best
properties at the 2Mhz range which is good cause thats the speed we run
it at. This is of course assuming that TX/RX go down the correct wires
as the pairing used here is for CAT5 cables.
Also, If it's not provisioned in fibre, what cable do the telco use
?????
This strikes me as akin to the argument you will often find in HiFi
shops, 'Dont use the manufacturers supplied interconnect leads'. A very
valid argument but at the end of the day it works and unless you happen
to have a good ear for these things you probably won't notice the
difference. (BTW I can tell the difference but the point is the same
......)
Cheers
Phil
Lan Systems. hopefully we'll have a 100Mhz TDR soon :-)
> ----------
> From: Jake Messinger[SMTP:jake@ams.com]
> Reply To: Jake Messinger
> Sent: Friday, April 25, 1997 3:50 PM
> To: Luther Keal
> Cc: support@livingston.com; Joel_M_Snyder@Opus1.COM;
> portmaster-users@livingston.com
> Subject: Re: What do the db levels Mean
>
> On Fri, 25 Apr 1997, Luther Keal wrote:
>
> > Support,
> >
> > OK folks, I'm runnning CT-1 and using the 20' cables out of the box
> > supplied with the PM-3. Should we use different cables, (not that I
> think
> > we should by the way).
>
> Hey lets not start a panic! Ask Livingston first before
> suggesting that we NOT use the cables in the box.
>
> This discussion has come up before about using cat 5 for serial
> connections but I dont believe specifically about rj-48
>
> Regarding serial. Afer that discussion, I did A LOT of testing on cat
> 5
> passing serial data to printers at 9600 baud over varying lengths
> versus 8
> conductor 4 pair shielded wire. I found that I had NO problems at 9600
> baud.
>
> Due to the nature of t1 connections, I would think that you would need
> to use a properly speced cable for it. I do NOT think Livingston would
> ship a $20,000 product with the wrong cables.
>
> Just my 9 cents.
>
> ~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._
> .,-*~
> Jake Messinger 713-772-6690 jake@ams.com
> Advanced Medical Systems, Inc. jake@uh.edu
> Houston, Texas http://www.ams.com/~jake
> ~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._
> .,-*~
>
> One should not be measured by his/her ascii art ability.
>