X-Envelope-to: NOVELL@SUVM.BITNET
X-VMS-To: IN%"NOVELL@SUVM.BITNET"
X-VMS-Cc: JRD
MIME-version: 1.0
Content-type: TEXT/PLAIN; CHARSET=US-ASCII
Content-transfer-encoding: 7BIT
Newsgroups: bit.listserv.novell
Date:         Wed, 29 Jul 1992 08:56:58 -0600
Reply-To:     Novell LAN Interest Group <NOVELL@SUVM.BITNET>
From:         Joe Doupnik <JRD@USU.BITNET>
Subject:      Re: RG58 CABLE QUESTION

>
>A question about RG58 cable:
>
>When we installed our net, we ordered RG58 thinet cable.  What came in was
>ALL copper...solid copper center wire & copper braiding.  We recently
>ordered more to add another trunk to the 8-port repeater.  I didn't
>notice until I had it strung through 3 floors that the cable was different.
>The center wire is braided silver strands (I think aluminum) and the
>outer braiding is also silver-colored.  It was nearly a nightmare getting
>the stranded center wire into the BNC connectors without fraying it and
>causing it to short.  After a while, it got easier, but still no picnic.
>While I thought we ordered the same number, after checking, the number
>is the same except it has a "-A" after it.
>
>Should I anticipate any problems with this cable later?
>Is it better, worse, the same...?
>Thanks,
>Bob
>Bob Smith         Computer Center Coordinator
>Kent State University - East Liverpool Campus
>East Liverpool, Ohio  43920     (216)385-3805
-----------------
        Not good indications. The solid center conductor stuff is probably
53 Ohms, as a start, and that will cause much trouble later on. Hint on
this is don't buy RG58 for LANs; there are many variations of different
impedances and reflections WILL occur as they are joined later on. Instead
purchase purpose-made coax, white jacketed, stranded center conductor,
doubly shielded (stranded braid surrounding aluminum foil), foam dielectric,
close tolerance 50 Ohms. Such cable is made by Belden and sold by Digital
Equipment (DEC) for about $210/1000-foot reel; it went though many design
phases to get it done right. I don't know how many miles of this I've
purchased over the past several years.
        BNC connectors. Attaching these is the biggest headache long term.
One must have high quality BNC connectors (Amphenol 36775 or equivalent)
and a proper high quality crimp tool (and wire stripper). Please do not
accept non-branded BNCs. With those pieces in hand, literally, a little
practice makes perfect. However, experience here suggests that many people
have coordination problems when doing this: they cut back the braid and
plastic jacket too far, they expose too much center conductor wire and/or
leave strands loose, they shove the center conductor pin too far through
the connector (it's a snap fit), and they put braid/al foil into the BNC
connector body, etc. So, there's a "right" way and a "wrong" way, and careful
work (plus thought) will produce the "right" way. Things will go together
very nicely when done properly; it will look right and feel right. Because
of these coordination problems my place has about four approved people who do
know how and have the proper equipment; using them yields trouble free cables.
        Don't mix and match cables. Don't use generic RG58. Don't use cheap
stuff. Don't accept substitutes. Do get LAN grade 50 Ohm coax, Mil spec BNC
connectors (gold pins too), and matching crimp tools (expect to pay $60 and
up). When in doubt about components consult with someone who knows the
differences, and that excludes salespersons. If money and training time is
spent at this end it will save much grief later when segments go down for
mysterious reasons.
        Joe D.
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU