Re: Shieled ethernet cables in Germany
Absolutely correct. I ASSUMED that what was meant was that shielding the cable resulted in no better than a 6 dB reduction in cable-sourced emissions. Something you could check with a current probe. If an entire system is being tested then clearly other emission sources could mask any cable-sourced improvements. Ken Javor on 2/24/03 11:04 AM, drcuthbert at drcuthb...@micron.com wrote: > The fact that going from unshielded to shielded cable cut emissions by 6 dB > does not necessarily mean that the shield cut cable emissions by only 6 dB. It > could mean that the cable emissions have been greatly reduced but another part > of the system has emissions that are 6 dB below the original configuration. > Like pealing an onion and revealing the layers of EMI. > > Dave Cuthbert > Micron Technology > > -Original Message- > From: Ken Javor [mailto:ken.ja...@emccompliance.com] > Sent: Monday, February 24, 2003 7:22 AM > To: Jan Vercammen; emc-p...@majordomo.ieee.org > Subject: Re: Shieled ethernet cables in Germany > > > > To Jan Vercammen and Michael Nagel and the whole forum, > > If a decent shield only provides 6 dB of shielding effectiveness at best, > that is an indictment of the termination impedance(s) and Doug Smith is > right, other techniques need to be investigated for reducing emissions and > immunity. > > Ken Javor > > -- Ken Javor EMC Compliance Huntsville, Alabama 256/650-5261 This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Shieled ethernet cables in Germany
The fact that going from unshielded to shielded cable cut emissions by 6 dB does not necessarily mean that the shield cut cable emissions by only 6 dB. It could mean that the cable emissions have been greatly reduced but another part of the system has emissions that are 6 dB below the original configuration. Like pealing an onion and revealing the layers of EMI. Dave Cuthbert Micron Technology From: Ken Javor [mailto:ken.ja...@emccompliance.com] Sent: Monday, February 24, 2003 7:22 AM To: Jan Vercammen; emc-p...@majordomo.ieee.org Subject: Re: Shieled ethernet cables in Germany To Jan Vercammen and Michael Nagel and the whole forum, If a decent shield only provides 6 dB of shielding effectiveness at best, that is an indictment of the termination impedance(s) and Doug Smith is right, other techniques need to be investigated for reducing emissions and immunity. Ken Javor This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Shieled ethernet cables in Germany
To Jan Vercammen and Michael Nagel and the whole forum, If a decent shield only provides 6 dB of shielding effectiveness at best, that is an indictment of the termination impedance(s) and Doug Smith is right, other techniques need to be investigated for reducing emissions and immunity. Ken Javor on 2/24/03 4:04 AM, Jan Vercammen at jan.vercamm...@agfa.com wrote: > > > Hello, > > > I can confirm Doug's remarks, a badly designed Ethernet system shielding > can behave much > worse than an unshielded one. I have don EMC tests with foil-shielded TWP > and unshielded TWP. > If the shield and/or the connector are not connected properly then radiated > emissions and > susceptibility can be enhanced considerable. > > On the other hand in a well designed system - using proper (foil) shield > connection and a correct > RJ45-chassis connection - I have found that foil shielded TWP can lower the > radiated emissions > by a factor of 4-6dB and increase the immunity for conducted and radiated > emissions from 3Vrms > and 3V/m to almost 10Vrms and 10V/m, respectively (using a criteria of 10% > package loss). Most > problems are encountered with conducted immunity in the range below 40MHz > for 100BaseT. > The same remarks apply for Electric Fast Transients: foil shielded TWP can > double the immunity level. > > > Again, the shielding only works if the entire system uses proper > connector-chassis and connector-shield > connections. That means: > -1- use fingered RJ45 connectors to connect directly to the chassis (though > I have tested one product, > were we do the connection by means of a single spring - it works, I > have tested both foil and UTP). > All are new products have a chassis connection on the RJ45 connector > -2- the foil needs to be continuous across the cable-connector, so it > needs to be folded back in a 360 degree > fashion and connect to the metal plating of the jack. The drain wire > is also bend back and also contacts > the metal plating of the jack. > The cable I used was bought from a distributor. Depending were you > buy one can get probably all > kinds of performance levels. To my opinion one can check the cable > shield continuity by means of visual > inspection. > > Note that I did not test (braid) shielded cable. > > > > Kind regards, > > Jan Vercammen > > > > Kind regards, > > > Jan Vercammen > > > > > > > Doug Smith @majordomo.ieee.org on 02/22/2003 08:14:24 AM > > Please respond to Doug Smith > > Sent by: owner-emc-p...@majordomo.ieee.org > > > To: neve...@attbi.com > cc: emc-p...@majordomo.ieee.org > Subject: Re: Shieled ethernet cables in Germany > > > Hi Nevin, George, and the group, > > Although "screened" ethernet systems are favored in Europe, some of > them perform considerably worst than unshielded systems in terms of > emissions and immunity. Some poorly designed systems (use of pigtails > on shields) radiate more, and even the best systems cannot match the > immunity performance of unshielded systems in tests I helped perform > in Switzerland a few years ago. The paper, published at Roma94 is > posted on my site at: > > http://emcesd.com/pdf/roma94.pdf > > It is interesting to note that even good shielded systems can induce > failures of PCs in IEC 61000-4-4 by providing a low impedance path for > the common mode EMI to get "into the works" of the PCs, quite separate > issue from the data transmission itself. Unshielded systems do not do > this because of the CM chokes and balancing transformer design in the > interface circuity. > > Doug > > neve...@attbi.com wrote: >> To my knowledge, only when the Class B for Central-Office equipment has > to be >> met. >> >> Neven >> >>> Hello Group, >>> >>> I heard recently that shielded Ethernet cables have become something of >>> a customer-expectation-based defacto standard in Germany for >>> installation of network type ITE equipment (routers, switches, >>> firewalls, etc.) Can anyone confirm or comment on that. Is it like >>> that anywhere else? >>> >>> Thanks >>> >>> George Stults >>> WatchGuard Technologies Inc. >>> > > -- > --- > ___ _ Doug Smith > \ / ) P.O. Box 1457 > = Los Gatos, CA 95031-1457 > _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 > / /\ \ ] / /\ \ Mobile: 408-858-4528 > | q-( ) | o |Email: d...@dsmith.org > \ _ /]\ _ / Website: ht
Re: Shieled ethernet cables in Germany
Hello, I can confirm Doug's remarks, a badly designed Ethernet system shielding can behave much worse than an unshielded one. I have don EMC tests with foil-shielded TWP and unshielded TWP. If the shield and/or the connector are not connected properly then radiated emissions and susceptibility can be enhanced considerable. On the other hand in a well designed system - using proper (foil) shield connection and a correct RJ45-chassis connection - I have found that foil shielded TWP can lower the radiated emissions by a factor of 4-6dB and increase the immunity for conducted and radiated emissions from 3Vrms and 3V/m to almost 10Vrms and 10V/m, respectively (using a criteria of 10% package loss). Most problems are encountered with conducted immunity in the range below 40MHz for 100BaseT. The same remarks apply for Electric Fast Transients: foil shielded TWP can double the immunity level. Again, the shielding only works if the entire system uses proper connector-chassis and connector-shield connections. That means: -1- use fingered RJ45 connectors to connect directly to the chassis (though I have tested one product, were we do the connection by means of a single spring - it works, I have tested both foil and UTP). All are new products have a chassis connection on the RJ45 connector -2- the foil needs to be continuous across the cable-connector, so it needs to be folded back in a 360 degree fashion and connect to the metal plating of the jack. The drain wire is also bend back and also contacts the metal plating of the jack. The cable I used was bought from a distributor. Depending were you buy one can get probably all kinds of performance levels. To my opinion one can check the cable shield continuity by means of visual inspection. Note that I did not test (braid) shielded cable. Kind regards, Jan Vercammen Kind regards, Jan Vercammen Doug Smith @majordomo.ieee.org on 02/22/2003 08:14:24 AM Please respond to Doug Smith Sent by: owner-emc-p...@majordomo.ieee.org To: neve...@attbi.com cc: emc-p...@majordomo.ieee.org Subject: Re: Shieled ethernet cables in Germany Hi Nevin, George, and the group, Although "screened" ethernet systems are favored in Europe, some of them perform considerably worst than unshielded systems in terms of emissions and immunity. Some poorly designed systems (use of pigtails on shields) radiate more, and even the best systems cannot match the immunity performance of unshielded systems in tests I helped perform in Switzerland a few years ago. The paper, published at Roma94 is posted on my site at: http://emcesd.com/pdf/roma94.pdf It is interesting to note that even good shielded systems can induce failures of PCs in IEC 61000-4-4 by providing a low impedance path for the common mode EMI to get "into the works" of the PCs, quite separate issue from the data transmission itself. Unshielded systems do not do this because of the CM chokes and balancing transformer design in the interface circuity. Doug neve...@attbi.com wrote: > To my knowledge, only when the Class B for Central-Office equipment has to be > met. > > Neven > >>Hello Group, >> >>I heard recently that shielded Ethernet cables have become something of >>a customer-expectation-based defacto standard in Germany for >>installation of network type ITE equipment (routers, switches, >>firewalls, etc.) Can anyone confirm or comment on that. Is it like >>that anywhere else? >> >>Thanks >> >>George Stults >>WatchGuard Technologies Inc. >> -- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord
RE: Shieled ethernet cables in Germany
Hi Doug and the group, I think the issue is a bit more complex than that. The cables can be an effective antenna in both cases but the reasons are not the exactly the same. Speaking for shielded cables the failures you have seen are (from my experience) the already mentioned pigtails, the connection of the shield on the RJ-45 connector and - especially in the case of PCs - the far from ideal connection of the front panel of the card to the enclosure. The failures you have seen on shielded cables result quite often from this, in the case of immunity as well as emission. IMHO a shielded cable *needs* a good enclosure and a low impedance path to protective ground but is less sensitive to "noisy" cards whereas unshielded cables are less sensitive to not so good enclosures but more to *noisy* cards within the enclosure - especially bad ground in the area of the signal transmitter (the Ethernet PHY). Your opinion? Best regards, Michael > -Original Message- > From: Doug Smith [mailto:d...@emcesd.com] > Sent: Samstag, 22. Februar 2003 08:14 > To: neve...@attbi.com > Cc: emc-p...@majordomo.ieee.org > Subject: Re: Shieled ethernet cables in Germany > > > > Hi Nevin, George, and the group, > > Although "screened" ethernet systems are favored in Europe, some of > them perform considerably worst than unshielded systems in terms of > emissions and immunity. Some poorly designed systems (use of pigtails > on shields) radiate more, and even the best systems cannot match the > immunity performance of unshielded systems in tests I helped perform > in Switzerland a few years ago. The paper, published at Roma94 is > posted on my site at: > > http://emcesd.com/pdf/roma94.pdf > > It is interesting to note that even good shielded systems can induce > failures of PCs in IEC 61000-4-4 by providing a low impedance > path for > the common mode EMI to get "into the works" of the PCs, quite > separate > issue from the data transmission itself. Unshielded systems do not do > this because of the CM chokes and balancing transformer design in the > interface circuity. > > Doug > > neve...@attbi.com wrote: > > To my knowledge, only when the Class B for Central-Office > equipment has to be > > met. > > > > Neven > > > >>Hello Group, > >> > >>I heard recently that shielded Ethernet cables have become > something of > >>a customer-expectation-based defacto standard in Germany for > >>installation of network type ITE equipment (routers, switches, > >>firewalls, etc.) Can anyone confirm or comment on that. Is it like > >>that anywhere else? > >> > >>Thanks > >> > >>George Stults > >>WatchGuard Technologies Inc. > >> > > -- > --- > ___ _ Doug Smith > \ / ) P.O. Box 1457 >= Los Gatos, CA 95031-1457 > _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 > / /\ \ ] / /\ \ Mobile: 408-858-4528 > | q-( ) | o |Email: d...@dsmith.org > \ _ /]\ _ / Website: http://www.dsmith.org > --- > > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Shieled ethernet cables in Germany
Hi Nevin, George, and the group, Although "screened" ethernet systems are favored in Europe, some of them perform considerably worst than unshielded systems in terms of emissions and immunity. Some poorly designed systems (use of pigtails on shields) radiate more, and even the best systems cannot match the immunity performance of unshielded systems in tests I helped perform in Switzerland a few years ago. The paper, published at Roma94 is posted on my site at: http://emcesd.com/pdf/roma94.pdf It is interesting to note that even good shielded systems can induce failures of PCs in IEC 61000-4-4 by providing a low impedance path for the common mode EMI to get "into the works" of the PCs, quite separate issue from the data transmission itself. Unshielded systems do not do this because of the CM chokes and balancing transformer design in the interface circuity. Doug neve...@attbi.com wrote: > To my knowledge, only when the Class B for Central-Office equipment has to be > met. > > Neven > >>Hello Group, >> >>I heard recently that shielded Ethernet cables have become something of >>a customer-expectation-based defacto standard in Germany for >>installation of network type ITE equipment (routers, switches, >>firewalls, etc.) Can anyone confirm or comment on that. Is it like >>that anywhere else? >> >>Thanks >> >>George Stults >>WatchGuard Technologies Inc. >> -- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Shieled ethernet cables in Germany
To my knowledge, only when the Class B for Central-Office equipment has to be met. Neven > > Hello Group, > > I heard recently that shielded Ethernet cables have become something of > a customer-expectation-based defacto standard in Germany for > installation of network type ITE equipment (routers, switches, > firewalls, etc.) Can anyone confirm or comment on that. Is it like > that anywhere else? > > Thanks > > George Stults > WatchGuard Technologies Inc. > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Shieled ethernet cables in Germany
Hello Group, I heard recently that shielded Ethernet cables have become something of a customer-expectation-based defacto standard in Germany for installation of network type ITE equipment (routers, switches, firewalls, etc.) Can anyone confirm or comment on that. Is it like that anywhere else? Thanks George Stults WatchGuard Technologies Inc. This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
