>From Wiki: "Transceivers should be installed only at precise 2.5-metre intervals. This distance was chosen to not correspond to the wavelength of the signal; this ensures that the reflections from multiple taps are not in phase. These suitable points are marked on the cable with black bands."
It cites "IEEE Standard 802.3<https://en.wikipedia.org/wiki/802.3>-1985. IEEE<https://en.wikipedia.org/wiki/IEEE>. p. 121." bill ________________________________ From: cctalk <cctalk-boun...@classiccmp.org> on behalf of Pete Turnbull via cctalk <cctalk@classiccmp.org> Sent: Tuesday, January 23, 2018 1:54 PM To: cctalk@classiccmp.org Subject: Re: Ethernet cable (Was: Sun3 valuations?) On 23/01/2018 16:48, Grant Taylor via cctalk wrote: > On 01/23/2018 09:10 AM, Bill Gunshannon via cctalk wrote: >> If you didn't locate the transceivers on those black marks you would >> have had terrible performance as that affects collisions. Timing >> (among other things like grounding) was very important with that >> version of ethernet hardware. > > It's my understanding that the marks (black bands or other markings on > the sheath) were exactly one wavelength apart. Which from what I > remember ~> understand from my ham radio days is quite important. No, that's quite wrong. The marks are every 2.5m (8.2 feet) wich IIRC is 1/19th of a wavelength apart, the point being to try to minimise the likelihood of connections being made where they'd suffer constructive (additive) interference and to prevent transceivers being too close together. -- Pete Pete Turnbull