(re-send due to not reply-all'ing as required) Sorry, I think that came across wrong due to my wording -- we were told it wasn't general practice to screw the terminator directly to the intrusive tap, as you would with a BNC tee on thinnet. We were told to use a jumper to extend somewhat past the tap, if it was the last thing on the segment.
Ethan sneaked in a reply that mentions a lack of distance between the last tap's impedance bump and the end of the transmission line. Perhaps someone with more of a transmission line engineering background can confirm or deny that. Thanks, Jonathan On Tue, Jun 26, 2018 at 3:16 PM, Paul Koning <paulkon...@comcast.net> wrote: > > > > On Jun 26, 2018, at 3:07 PM, systems_glitch via cctalk < > cctalk@classiccmp.org> wrote: > > > > I've confirmed that I now have N connector intrusive taps! These have a N > > female connector on each end, like the leftmost transceiver in this > picture: > > > > https://oelzant.priv.at/~aoe/images/galleries/hardware/802_ > 3_transceivers/DSC_0927_med.jpg > > > > I seem to recall the CCNA instructor telling us that you weren't really > > supposed to screw a 50 ohm terminator onto an intrusive tap; I don't know > > if there's good reason for it or if it was just a general practice. > > I'm not sure if I understood that correctly. It sounds flat out wrong, > and it presumably would not be general practice because an Ethernet segment > with a missing terminator either doesn't work at all, or works very poorly. > > An Ethernet segment must have a 50 ohm terminator at each end (and nowhere > else). Always. The spec is crystal clear about this, and so is elementary > transmission line physics. > > If you have an intrusive (connectorized) tap, installed at the very end of > the cable, the other side of the tap must have a terminator since that's > the end of the segment. > > I once saw an article in a magazine ("DEC Professional" or "RSTS > Professional", a US based rag for PDP11 users) that talked about thick and > thin Ethernet. It mentioned that you can connect the two -- which is > correct. But it showed the wrong way -- with a T connector and a > terminator attached to one of the legs of the T. In other words, a > "terminator" in the MIDDLE of the segment. The correct way, of course, is > a BNC to N adapter, and you have to use the thin Ethernet length and > station limits. > > So it sounds like your instructor was just as ignorant as the writers of > that magazine. > > paul > > >