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

[systems_glitch]

(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 <paulkoning at comcast.net> wrote:

>
>
> > On Jun 26, 2018, at 3:07 PM, systems_glitch via cctalk <
> cctalk at 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
>
>
>