Ed, if I have a transmission line with a noise source on one end and a victim circuit at the other, it sounds reasonable to put a break in that line to block the noise. This is how moats get born. What happens if I have multiple transmission lines? It should stand to similar reason that if putting a break in one line is going to help, I will have to put a break in each line capable of delivering substantial unwanted noise energy to my victim circuit. There can be some mighty sneaky transmission structures lurking around circuit boards. Inserting moats in the wrong place at the wrong time can do bad bad things. Often it is more effective to shunt noise somewhere else by placement and routing than to try and break all the possible transmission paths. In other cases a combination of measures is appropriate. I find it helpful to think in terms of what the fields are doing, or are likely to do. Steve. At 01:38 PM 5/25/2006, Ed Troy wrote: >If you have a circuit board that requires a split gnd plane over a >small section of the board, and you have several ground planes, >should only one have the split (the one nearest the side containing >the components that require analog ground) while the rest of the >ground planes are continuous, or should the split section be on all >ground layers? I would think that you should only have it on one >layer. Also, if it should only be on one layer, I would imagine it >would be best to connect it to the digital ground with one, and only >one, via. Is that generally correct? What are some good references >for layer stackups, etc? I know I saw one, once, but can't remember where. > >Ed > > >------------------------------------------------------------------ >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: >//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: > //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: //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: //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