Thicknet/10base5 Test Segment: The Cable is In!

[systems_glitch]

So then we're in agreement that screwing the N terminator directly to an
intrusive tap shouldn't make a difference? No need for a jumper off the end
of the tap for the terminator to live on?

As a high school CCNA hopeful, I accepted this as, "it's what you do," and
I hadn't really given it any thought since then, as I hadn't had to mess
with thicknet since then. I agree that it doesn't really make sense when
you actually *think* about it, and, like I said to start with, it's what I
recall being told back then anyway -- I could be remembering wrong to start
with :)

Thanks,
Jonathan

On Tue, Jun 26, 2018 at 8:02 PM, Paul Koning via cctalk <
cctalk at classiccmp.org> wrote:

>
>
> > On Jun 26, 2018, at 7:20 PM, Eric Smith via cctalk <
> cctalk at classiccmp.org> wrote:
> >
> > On Tue, Jun 26, 2018 at 4:37 PM, Chuck Guzis via cctalk <
> > cctalk at classiccmp.org> wrote:
> >
> >> On 06/26/2018 03:15 PM, Grant Taylor via cctalk wrote:
> >>
> >>> I can only guess that having a terminator too close interferes with or
> >>> weakens the signal too much in some way.
> >>
> >> Exactly what would the effect be?  I recall putting terminators on
> >> 10base2 coax just hanging off one leg of a BNC tee.  Really, no distance
> >> at all.  Didn't seem to affect speed or distance.
> >
> >
> > If the termination resistance matches the characteristic impedance of the
> > cable, there should be no difference. When terminated properly, there is
> no
> > reflection from the terminator, so it looks equivalent to an infinitely
> > long cable, though in practical terms with less leakage than an "actual"
> > infinitely long cable would have.
> >
> > Of course, in reality it will never be terminated perfectly, so there
> will
> > always be a small reflection, which can be seen with a TDR. If the
> > termination resistance is pretty close, the reflection will be small
> enough
> > not to matter at all for Ethernet.
>
> Exactly.  And the specs for the Ethernet terminator are quite tight for
> that reason.  The connectors themselves have non-zero impact but very
> small; they are high quality microwave grade connectors.
>
> You got the definition precisely correct: a terminator is a device that is
> electrically equivalent to an infinite length cable.  You can cut the
> unused part of a coax anywhere you want and put a terminator at that point
> instead, and as far as the rest of the cable is concerned nothing has
> changed (apart from very small effects because the components are not
> perfect).
>
> There clearly is confusion about what terminators are and how they work.
> It's all perfectly straightforward elementary classic E & M, and any
> halfway decent RF theory textbook will make things clear.  Even a source as
> elementary as the ARRL Radio Amateur Handbook will serve.
>
>         paul
>
>
>