In fact a standard for 150 Ohms STP cable does exist but is intended for
FDDI Token Ring applications, to which the ANSI X3.263 standard applies, and
I assume not for Ethernet. Maybe the story I heard was about someone who
used this type of cable for Ethernet.
Although it was a logical guess, the 150 ohms value is not from "the
combination of the 100 ohm characteristic impedance and the 50 ohm output
from equipment".
Sorry for the confusion,
Eric
-----Original Message-----
From: KC CHAN [PDD] [SMTP:kcc...@hkpc.org]
Sent: Sunday, September 09, 2001 8:52 PM
To: pronc...@cisco.com; james_al...@milgo.com
Cc: emc-p...@majordomo.ieee.org
Subject: RE: STP vs FTP Ethernet cables (2)
I guess this 150 ohms is from the combination of the 100 ohm
characteristic impedance and the 50 ohm output form equipment, like the
power amplifier for conducted immunity test.
>>> "Allan, James" <james_al...@milgo.com> 09/07/01 09:03pm >>>
Paolo: Try this link to Quabbin wire company. It is a product
selector
guide with the types of wire used for different applications. All
Ethernet
applications are 100 ohm characteristic impedance and only have
overall
shields if shielded. Telecom cable (T1, DSL etc.) if shielded, are
also 100
ohm but the shield (if present) is over the individual wire pairs
with no
overall shield. I find no reference to standard Ethernet cable at
150 ohms.
LINK http://www.quabbin.com/finder/finder.cgi?cmd=app_form
Jim Allan
Manager, Engineering Services
Nextira Solutions LLC
1619 N Harrison Parkway
Sunrise, FL, 33323
E-mail james_al...@milgo.com
Phone (954) 846-3720
Fax (954) 846-6282
> -----Original Message-----
> From: Paolo Roncone [SMTP:pronc...@cisco.com]
> Sent: Friday, September 07, 2001 5:28 AM
> To: "Meunier, Eric"
> Cc: emc-p...@majordomo.ieee.org
> Subject: RE: STP vs FTP Ethernet cables (2)
>
> Eric,
>
> this 150 ohm story of STP cables sounds completely new to me.
Also, my
> understanding is that both UTP and STP are used for 10bT ethernet.
> In the STP definition of IEEE802.3, there is no mention about
different
> characteristic impedances from the required 100ohm of 10bT.
> Unfortunately I haven't yet received an answer to my original
question as
> to how STP cables should be actually made (shielded twisted pairs
vs
> overall shield) .
> As I already said in previous e-mails, the "STP" cables that I got
look
> pretty much the same as "FTP" cables, that is they have just an
overall
> shield (aluminum foil) around all wires. And they are all declared
to be
> 100 ohms.
>
> Paolo
>
>
> At 16:56 06/09/2001 -0400, you wrote:
>
>
>
> Paolo,
>
> You may want to check if the FTP cable has a 100 Ohms
characteristic
> impedance which would make it compatible with interfaces
designed
> for UTP
> cable. STP cable is supposed to have a 150 Ohms impedance
which is
> not
> compatible with standard 10baseT interfaces which are
usually
> designed for
> UTP.
>
> Eric
>
> ===================================
>
> Eric Meunier
> Hardware Architect
>
> E-mail: eric.meun...@ca.kontron.com <
<mailto:emeun...@teknor.com>>
>
> Kontron Communication Inc. (Teknor)
> 616, rue Cure-Boivin
> Boisbriand, Quebec
> Canada, J7G 2A7
>
> Tel: 1-450-437-4661 ext. 2419
> Fax: 1-450-437-8053
>
> Web: <http://www.teknor.com/> < <http://www.teknor.com/>>
>
>
>
> -----Original Message-----
> From: Paolo Roncone [SMTP:pronc...@cisco.com]
> Sent: Thursday, September 06, 2001 4:18 AM
> To: Doug McKean
> Cc: EMC-PSTC Discussion Group
> Subject: Re: STP vs FTP Ethernet cables (2)
>
> Doug,
>
> I re-paste the first part of the definition in IEEE
802.3
> (2000):
>
> <<1.4.249 shielded twisted-pair (STP)cable: An
electrically
> conducting cable,comprising one or more ele-
> ments,each of which is individually shielded.There
may be an
> overall
> shield,in which case the cable is
> referred to as shielded twisted-pair cable with an
overall
> shield
> (from ISO/IEC 11801:1995)>>
>
> My understanding is that "elements" should refer to
> individual PAIRS
> (signal/return), rather than single wires. But - as I said
in my
> previous
> e-mail - I'd like to check whether this is put into practice
by some
> vendors. So far I didn't get any clue on this.
> The STP cables that I found so far (form a couple of
> vendors) have
> just an OVERALL shield around all wires, and these are
identical to
> FTP
> (Foiled Twisted Pair) cables that are also on the market.
> I agree with you, something doesn't sound right...
>
> Paolo
>
>
> At 09:36 05/09/2001 -0700, Doug McKean wrote:
>
>
>
> Paolo Roncone wrote:
> >
> > The reason of my inquiry is that we bought
samples
> of
> "STP" and
> "FTP"
> > cat.5 cables for 10bT ethernet
applications from
> different
> vendors
> and to
> > our surprise we discovered that both "STP"
and
> "FTP" types
> have an
> > overall (external) shield made of aluminum
foil,
> but no
> shields on
> individual
> > wires or wire couples (as per 802.3
definition
> above).
>
> Maintaining a characteristic impedence of a
twisted
> pair
> by shielding the individual wires of that
twisted
> pair?
>
> Something doesn't sound right.
>
> - Doug McKean
>
>
>
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--------------------------------------------------------------------------
> --
> ---
> Paolo Roncone
> EMC Compliance Engineer - Cisco Photonics Italy
> via Philips 12 - Monza (MI) 20052
> <mailto:pronc...@cisco.com> <
<mailto:pronc...@cisco.com>>
> phone: +39 039209 1538
> fax: +39 039209 2036
>
>
>
> -------------------------------------------
> This message is from the IEEE EMC Society Product Safety
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--------------------------------------------------------------------------
> -----
> Paolo Roncone
> EMC Compliance Engineer - Cisco Photonics Italy
> via Philips 12 - Monza (MI) 20052
> <mailto:pronc...@cisco.com>
> phone: +39 039209 1538
> fax: +39 039209 2036
>
>
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