Any chance you have hard numbers that you measured? I am curious to know how bad dispersion really is in bad cables. -----Original Message----- From: Zabinski, Patrick [mailto:zabinski.patrick@xxxxxxxx] Sent: Tuesday, October 28, 2008 7:45 PM To: si-list@xxxxxxxxxxxxx; Bill Dempsey Subject: RE: [SI-LIST] Re: SMA cable for TDR To characterize dispersion, group delay with a VNA is optimal. To see the effects of dispersion, TDR (assuming good/fast edges) is great. Eye diagrams can also be useful, but it's more difficult to separate out the effects of dispersion from discontinuities, crosstalk, ... As for noticing the effects of dispersion, we generally see it most when using economical (i.e., poor performing) cables. We were once ordering passive probes from a company that had 18" leads; the coax was relatively small diameter (roughly 0.200"). > Pat, > I'd like to learn a bit about the 'noticeable dispersion' in the coax > cables. I had a chance to measure the really nice Gore > cables and up to > 20GHz the VNA I was using showed flat group delay. > > What method do you use to measure coax cable dispersion? How > noticeable was > it? > > Thanks, > Bill > ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net 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