[SI-LIST] Re: Low-Q Controlled-ESR Bypass Capacitors

John,

FaradFlex and other thin laminates are good and useful, BUT
- they do not eliminate modal resonances until after you reduce
the thickness to about 0.5 mils or less
- regardless of the laminate thickness, low-ESR capacitors will
still have a tendency to create an antiresonance peak coming
from the static capacitance of the planes and the cumulative
inductance of bypass capacitors; and the thinner the laminate,
the harder to eliminate this antiresonance
- unless you have advanced power sources not needing bulk
capacitors at all, low-ESR ceramic capacitors will still have
a tendency to create antiresonances with the bulk capacitors

Eventually it all boils down to transient noise.  As it was
shown, the minute we deviate from a flat RL-like impedance
profile, we pay a penalty in increased noise.

Regards,
Istvan



Hill, John wrote:

>Istvan,
>
>If the capacitor vendors will not make the low Q capacitors that we
>need, then we will just have to find a different solution. The PCB
>materials are wonderfully lossy at high frequencies and should make fine
>capacitors. All we need to do is use the FARADFLEX Material from
>Oak-Mitsui to increase the capacitance per square inch of PCB.=20
>
>With a board size of 50 square inches here are the capacitance values
>they say can be achieved:
>=20
>ZBC2000 16 nF
>ZBC1000 32 nF
>BC24 40 nF
>BC16 64 nF
>BC12 76 nF
>BC8 124 nF
>BC12TM 180 nF
>BC16T 440 nF
>
>Here is link to their web site:
>
>http://www.oakmitsui.com/pages/advancedTechnology/faradFlex.asp
>
>If there are any capacitor vendors out there please let me know why I
>should buy high Q capacitors that will resonate with the PCB and each
>other. These High Q resonances will make for EMC problems, but we can
>fix the problem by not buying high Q capacitors.=20
>
>Best regards,
>
>John
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>On Behalf Of Hill, John
>Sent: Thursday, May 25, 2006 11:17 AM
>To: istvan.novak@xxxxxxxxxxx; Istvan.Novak@xxxxxxx
>Cc: si-list
>Subject: [SI-LIST] Low-Q Controlled-ESR Bypass Capacitors
>
>Istvan,
>
>I have just finished reading your paper: "Overview of Some Options to
>Create Low-Q Controlled-ESR Bypass Capacitors". I think it is a good
>idea. But I read in your paper: "as of today no commercially available
>such component exists"
>
>That was back in 2004. Can we buy then yet?
>
>Best regards,
>
>John
>
>-----Original Message-----
>From: istvan.novak@xxxxxxxxxxx [mailto:istvan.novak@xxxxxxxxxxx]=3D20
>Sent: Wednesday, May 24, 2006 9:30 PM
>To: Hill, John; Istvan.Novak@xxxxxxx
>Cc: steve weir; Larry Smith; Mark.Randol@xxxxxxxxxx; si-list
>Subject: Re: [SI-LIST] Re: Capacitors arrays. worth it or not?
>
>John,
>
>Yes, you are correct, what determines the series resonance frequency is
>the capacitance and the total loop inductance of the mounted part, the
>body inductance will be part of it.
>
>There are the following clarifications.  I would not use the length of
>an 0508 capacitor body to estimate the quarter-wave resonance.  As larry
>pointed out it is better to use the height of the part, which is about
>30-50 mils for a typical 0508 capacitor.  Also, because the vertical
>transmission line is loaded with the many capacitor plates, we end up
>with a heavily loaded transmission line, where the approximate time of
>flight is tpd~sqrt(LC) where L is the vertical inductance and C is the
>total capacitance.
>
>Regards,
>
>Istvan Novak
>SUN Microsystems
>
>
>From: "Hill, John" <jhill@xxxxxxxxxx>
>Date: Wed May 24 16:58:36 CDT 2006
>To: Istvan.Novak@xxxxxxx
>Cc: steve weir <weirsi@xxxxxxxxxx>, Larry Smith =
><LSMITH@xxxxxxxxxx>,=3D20
>       Mark.Randol@xxxxxxxxxx, si-list <si-list@xxxxxxxxxxxxx>
>Subject: [SI-LIST] Re: Capacitors arrays. worth it or not?
>
>Istvan,
>=3D20
>
>Yes, I ran the numbers:
>
>=3D20
>
>Electrical length of AVX 0508 LICC is =3D3D physical length * square =
>root
>=3D
>of
>Dielectric Constant.=3D20
>
>The Dielectric Constant is somewhere above 10K. Let's use 10K.
>
>=3D20
>
>The wavelength is 4 time the quarter wavelength =3D3D 4 * the Electrical
>length =3D3D 4 * 1.27 mm * square root of 10K.
>
>=3D20
>
>Frequency =3D3D C / wavelength =3D3D C / 4 * 1.27 mm * square root of =
>10K =3D
>=3D3D 590
>MHz.=3D20
>
>=3D20
>
>But the resonance on the data sheet is 10 MHz.
>
>=3D20
>
>So I guess we are back to the lead inductance and the capacitance of the
>MLCC causing the series resonance.
>
>=3D20
>
>And this lead inductance can be reduced with a reduction in the loop
>area of the leads to the MLCC and by reducing the length of the leads. I
>am guessing that is why the IDC and X2Y capacitors work. They reduce the
>area of the loop of current feeding the capacitor. Is this correct?
>
>=3D20
>
>Best regards,
>
>=3D20
>
>John
>
>=3D20
>
>=3D20
>
>=3D20
>
>________________________________
>
>From: Istvan.Novak@xxxxxxx [mailto:Istvan.Novak@xxxxxxx]=3D20
>Sent: Wednesday, May 24, 2006 4:49 PM
>To: Hill, John
>Cc: steve weir; Larry Smith; Mark.Randol@xxxxxxxxxx; si-list
>Subject: Re: [SI-LIST] Re: Capacitors arrays. worth it or not?
>
>=3D20
>
>John,
>
>The series resonance frequency of the mounted capacitor does=3D20
>not directly relate to the open-ended transmission line of=3D20
>the capacitor body.  The vertical transmission line that=3D20
>Larry referred to has high losses, partly because of the metal=3D20
>and dielectric losses, but also due to the electrical loading
>of the plates.  You can get this kind of model described in:
>"Slow Wave Causal Model for Multi Layer Ceramic Capacitors"
>on http://home.att.net/~istvan.novak/papers.html
>
>Regards,
>Istvan
>
>
>
>Hill, John wrote:
>
>
>
>Steve,
>=3D20
>I am not so sure of this. In the MLCC there is a transmission line with
>an end that is open. It is the open 1/4 wavelength transmission line
>that provides the low impedance on the other side of the part.
>Specifically, a 1/4 wavelength away from the open is a short.=3D3D20
>=3D20
>In the IDC part the end is shorted, not open. There is a difference and
>I am uncertain how to predict the resonance. That is why Larry's
>viewpoint is important. It provided a better understand of the fields in
>the parts and why the resonance occurs in the first place. I would like
>to understand the IDC parts as well as we now understand the MLCC parts.
>=3D20
>Can anyone explain to me the physics behind the IDC resonance as
>compared to the MLCC resonance?=3D3D20
>=3D20
>I would also like to know the Dielectric constant of the MLCC ceramic to
>run the numbers and confirm the electrical length of the MLCC part. It
>would be interesting to confirm the measured series resonance is truly
>predicted by the 1/4 wavelength of the MLCC parts.
>=3D20
>John
>=3D20
>-----Original Message-----
>From: steve weir [mailto:weirsi@xxxxxxxxxx]=3D3D20
>Sent: Wednesday, May 24, 2006 4:12 PM
>To: Hill, John; Larry Smith; Mark.Randol@xxxxxxxxxx; si-list
>Subject: RE: [SI-LIST] Re: Capacitors arrays. worth it or not?
>=3D20
>John, the physics is the same for an IDC.  The only difference is=3D3D20
>that you multiple coupled lines in each part of Larry's model.  =3D
>Until=3D3D20
>you get to really high frequency, you can simply replace those =
>with=3D3D20
>smaller equivalent inductance of Ls - Lm.
>=3D20
>Regards,
>=3D20
>=3D20
>Steve.
>At 10:59 AM 5/24/2006, Hill, John wrote:
> =3D20
>
>       Larry,
>       =3D20
>       Your analysis of a capacitor as a transmission line is very
>insightful.
>       It explains the physics behind why a MLCC has a series
>resonance. I
>          =3D20
>
>then
> =3D20
>
>       tried to apply the same technique to an IDC capacitor with both
>       terminals of the capacitor on both sides of the part.
>       =3D20
>       I was not able to determine where the first resonance would be.
>How
>       would you apply this technique to an IDC capacitor? And for that
>matter
>       does anyone know where the first resonance would be for an IDC
>       capacitor?
>       =3D20
>       Best regards,
>       =3D20
>       John
>       =3D20
>       -----Original Message-----
>       From: Larry Smith [mailto:LSMITH@xxxxxxxxxx]
>       Sent: Tuesday, May 23, 2006 12:47 PM
>       To: weirsi@xxxxxxxxxx; Hill, John; Mark.Randol@xxxxxxxxxx;
>si-list
>       Subject: RE: [SI-LIST] Re: Capacitors arrays. worth it or not?
>       =3D20
>       Steve, John - here is another interesting way to look at it.
>When a
>       ceramic capacitor is mounted such that the capacitor plates are
>          =3D20
>
>parallel
> =3D20
>
>       to the PCB plates, the capacitor forms a vertical transmission
>line
>          =3D20
>
>with
> =3D20
>
>       inductance per unit length and capacitance per unit length.  The
>far
>          =3D20
>
>end
> =3D20
>
>       of the transmission line is open circuit (air) and the near end
>is
>       nearly shorted (PCB power planes present a very low impedance to
>the
>       mounted capacitor).  This makes a quarter wavelength resonator
>similar
>       to a 50 Ohm transmission line that is open on one end.  At the
>quarter
>       wavelength frequency, the open circuit at the far end becomes a
>low
>       impedance node at the near end.  This is the series resonant
>frequency
>       of the capacitor.  The peaks and dips that you might see beyond
>the
>       series resonance of the capacitor are associated with the half,
>3/4,
>       full,  1 1/4, etc, wavelengths of the capacitor transmission
>line.
>       =3D20
>       To see this effect, you must mount the capacitor on vias and
>pads that
>       have less inductance than the capacitor itself otherwise the
>resonance
>       is completely dominated by the mounting inductance.  Tall
>capacitors
>       with very low ESR show this effect the best.  I was evaluating a
>bunch
>       of capacitors one time and the 33nF NPO 2220 size capacitor
>strongly
>       exhibited these properties.  It is very tall and has low ESR
>because of
>       the many, many plates.  I had it mounted on a fixture estimated
>at 83pH
>       but the inductance associated with the capacitor itself was
>about 1 nH.
>       There were perhaps a half a dozen dips and peaks beyond series
>          =3D20
>
>resonance
> =3D20
>
>       associated with the transmission line properties of the
>capacitor.
>       =3D20
>       David Hockanson and I did a couple of papers on this at 2002 and
>2003
>       ECTC conference and another one at 2005 Design Con.  You can
>actually
>       use the transmission line properties of a capacitor to develop a
>ladder
>       SPICE model and extract the element values.  The model
>accurately
>       predicts the reduction of inductance and the increase in ESR of
>a
>       capacitor mounted on low inductance pads.  This is important to
>          =3D20
>
>simulate
> =3D20
>
>       the parallel resonance that may occur between two capacitors or
>between
>       a capacitor and power planes.  Ceramic capacitors have a lot
>more ESR
>       and less ESL than might be expected from a simple RLC model
>beyond
>       series resonance.
>       =3D20
>       Mounting capacitors with the plates perpendicular to the PCB
>planes
>       (rather than parallel) eliminates or at least greatly changes
>this
>       mechanism.  As Istvan mentioned, the resonances are very much
>reduced.
>       I believe that there is still an increase in ESR and a reduction
>of ESL
>       beyond series resonance as the current does not want to get very
>far
>       away from the PCB power planes (big inductive loop).  Once
>again, you
>       would have to mount the capacitors on very low inductance mounts
>in
>       order to see this.
>       =3D20
>       Regards,
>       Larry Smith
>       Altera Corporation
>       =3D20
>       =3D20
>       -----Original Message-----
>       From: si-list-bounce@xxxxxxxxxxxxx
>          =3D20
>
>[mailto:si-list-bounce@xxxxxxxxxxxxx]
> =3D20
>
>       On Behalf Of steve weir
>       Sent: Monday, May 22, 2006 11:27 PM
>       To: Hill, John; Mark.Randol@xxxxxxxxxx; si-list
>       Subject: [SI-LIST] Re: Capacitors arrays. worth it or not?
>       =3D20
>       John, you've got it.  The vertical orientation makes for N very
>small
>       cavities all acting in parallell.  Hence, the secondary
>resonance
>       occurs at a much higher frequency.
>       =3D20
>       Regards,
>       =3D20
>       =3D20
>       Steve.
>       At 01:50 PM 5/22/2006, Hill, John wrote:
>          =3D20
>
>               Steve,
>               =3D20
>               I'm sorry to be a little thick on this issue, but I may
>be getting
>                    =3D20
>
>the
> =3D20
>
>               two orientations confused. If I understand you
>correctly, the
>                    =3D20
>
>following
> =3D20
>
>               is true:
>               =3D20
>               It is Edie currents that keep the current concentrated
>in the lower
>               plates of a capacitor when the capacitor is mounted
>horizontally,
>                    =3D20
>
>which
> =3D20
>
>               we are defining as having the plates parallel to the
>board. This
>                    =3D20
>
>       creates
>          =3D20
>
>               a resonate cavity under the part.
>               =3D20
>               When the capacitor is mounted with the plates
>perpendicular to the
>                    =3D20
>
>       board
>          =3D20
>
>               the current flows through all the plates.
>               =3D20
>               Is this correct?
>               =3D20
>               John
>               =3D20
>               =3D20
>               =3D20
>               =3D20
>               ---------------------------------------
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>               legally privileged, proprietary or confidential
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>               recipient(s), or the employee or agent responsible for
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>               ---------------------------------------
>               -----Original Message-----
>               =3D20
>               From: steve weir [mailto:weirsi@xxxxxxxxxx]
>               Sent: Monday, May 22, 2006 2:41 PM
>               To: Hill, John; Mark.Randol@xxxxxxxxxx; si-list
>               Subject: Re: [SI-LIST] Re: Capacitors arrays. worth it
>or not?
>               =3D20
>               John, when the plates of a cap are parallel to the
>planes, eddy
>               currents block field penetration to the upper plates
>through the
>               cavity.  The field still goes around the terminal
>metalization.  This
>               makes a resonant cavity.
>               =3D20
>               Steve.
>               At 10:50 AM 5/22/2006, Hill, John wrote:
>                    =3D20
>
>                       Mark,=3D3D3D20
>                       =3D20
>                       We have uploaded an application note from
>American Technical
>                              =3D20
>
>Ceramics
> =3D20
>
>                       concerning placing capacitors vertical and
>horizontal. The URL is:
>                       =3D20
>=3D09
>http://si-list.org/files/tech_files/ATC%20select_cap_wireless.pdf
>                       =3D20
>                       I have also sent an e-mail to the application
>engineer about the
>                              =3D20
>
>       issue
>          =3D20
>
>                       of eddy currents limiting the field. The data in
>the application
>                              =3D20
>
>note
> =3D20
>
>                       does not look like it supports the idea and I do
>not understand the
>                       physics.=3D3D3D20
>                       =3D20
>                       John
>                       =3D20
>                       =3D20
>                       =3D3D3D20
>                       =3D20
>                       ---------------------------------------
>                       The information in this email and attachments
>hereto may contain
>                              =3D20
>
>               legally =3D3D3D
>                    =3D20
>
>                       privileged, proprietary or confidential
>information that is
>                              =3D20
>
>intended
> =3D20
>
>               for =3D3D3D
>                    =3D20
>
>                       a particular recipient. If you are not the
>intended recipient(s),
>                              =3D20
>
>or
> =3D20
>
>               the =3D3D3D
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> =3D20
>
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>=3D3D3D
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>                    =3D20
>
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>                              =3D20
>
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>                    =3D20
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>          =3D20
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>
>                       ---------------------------------------
>                       -----Original Message-----
>                       =3D20
>                       From: si-list-bounce@xxxxxxxxxxxxx
>                              =3D20
>
>               [mailto:si-list-bounce@xxxxxxxxxxxxx]
>                    =3D20
>
>                       On Behalf Of Mark Randol
>                       Sent: Monday, May 22, 2006 10:33 AM
>                       To: si-list
>                       Subject: [SI-LIST] Re: Capacitors arrays. worth
>it or not?
>                       =3D20
>                              =3D20
>
>                               -----Original Message-----
>                               From:
>si-list-bounce@xxxxxxxxxxxxx=3D3D3D3D20
>                               [mailto:si-list-bounce@xxxxxxxxxxxxx] On
>Behalf Of Jerry
>                                        =3D20
>
>Martinson
> =3D20
>
>                               =3D3D3D3D20
>                               I've always wondered how discrete cap
>performance is
>                                        =3D20
>
>affected=3D3D3D3D20
> =3D20
>
>                               if the caps plates are parallel with the
>underlying plane
>                                        =3D20
>
>or=3D3D3D3D20
> =3D20
>
>                               if they are perpendicular.  I'd think
>that having them
>                                        =3D20
>
>rolled=3D3D3D3D20
> =3D20
>
>                               90 degrees
>                               (perpendicular) might make them perform
>better in some=3D3D3D3D20
>                               regions.  I wonder how this would extend
>to arrays and=3D3D3D3D20
>                               whether arrays are configured rolled or
>not.  Does anyone=3D3D3D3D20
>                               know? =3D3D3D3D20
>                                        =3D20
>
>                       American Technical Ceramics (ATC) used to
>recommend 'vertical'
>                              =3D20
>
>               placement
>                    =3D20
>
>                       of their porcelain caps for just this reason.
>I've seen it make
>                              =3D20
>
>               several
>                    =3D20
>
>                       100MHz's of difference in the measured resonance
>frequency.  That
>                              =3D20
>
>was
> =3D20
>
>               on
>                    =3D20
>
>                       a relatively thick 2 layer PCB, so on a board
>with a thinner
>                              =3D20
>
>       component
>          =3D20
>
>                       to ground layer spacing this could be more
>significant <guess>.  I
>                       didn't find it on their web site, but here is
>their link.
>                       =3D20
>                       http://www.atceramics.com/
>                       =3D20
>                       Now how much of this was due to plate coupling
>to the substrate, or
>                       reduced effective capacitance and inductance
>because of current
>                              =3D20
>
>               crowding
>                    =3D20
>
>                       towards the new 'bottom' of all the plates,
>beats me.  It seems to
>                              =3D20
>
>me
> =3D20
>
>               in
>                    =3D20
>
>                       the horizontal orientation, the upper plates
>would have slightly
>                              =3D20
>
>more
> =3D20
>
>                       inductance due to the greater loop area.  Which
>effect dominates,
>                       capacitance or inductance? =3D3D3D3D20
>                       =3D20
>                       The problem at the time was fixed, so we didn't
>investigate
>                              =3D20
>
>further.
> =3D20
>
>                       --
>                       Mark Randol, RF Evaluation & Application
>Engineer
>                       Not speaking for my company, etc
>=3D09
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>       =3D20
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>                       http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>       =3D20
>       List technical documents are available at:
>                       http://www.si-list.org
>       =3D20
>       List archives are viewable at:
>                       http://www.freelists.org/archives/si-list
>       or at our remote archives:
>                       http://groups.yahoo.com/group/si-list/messages
>       Old (prior to June 6, 2001) list archives are viewable at:
>                       http://www.qsl.net/wb6tpu
>       =3D20
>          =3D20
>
>=3D20
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>=3D20
>or to administer your membership from a web page, go to:
>http://www.freelists.org/webpage/si-list
>=3D20
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>=3D20
>List FAQ wiki page is located at:
>                http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>=3D20
>List technical documents are available at:
>                http://www.si-list.org
>=3D20
>List archives are viewable at:    =3D20
>               http://www.freelists.org/archives/si-list
>or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
> =3D20
>=3D20
> =3D20
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
>or to administer your membership from a web page, go to:
>http://www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List FAQ wiki page is located at:
>                http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
>                http://www.si-list.org
>
>List archives are viewable at:    =3D20
>               http://www.freelists.org/archives/si-list
>or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
> =3D20
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
>or to administer your membership from a web page, go to:
>http://www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List FAQ wiki page is located at:
>                http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
>                http://www.si-list.org
>
>List archives are viewable at:    =20
>               http://www.freelists.org/archives/si-list
>or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
> =20
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
>or to administer your membership from a web page, go to:
>http://www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List FAQ wiki page is located at:
>                http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
>                http://www.si-list.org
>
>List archives are viewable at:     
>               http://www.freelists.org/archives/si-list
>or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
>  
>
>  
>

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

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