Re: [SLUG] coaxial ethernet

From: Robert Foxworth (rfoxwor1@tampabay.rr.com)
Date: Sat Aug 07 2004 - 22:55:16 EDT


> From google I found out that it is 10Base2 thin net.
>
>
> Eben King wrote:
>
> >On Sat, 7 Aug 2004, Joey Dale wrote:
> >
> >
> >
> >>I just got about 200ft of coaxial ethernet cable (RG85) with N
> >>connecters, and would like to hook my buddy into my network

If this is indeed 10Base2 then the designation for the coax
is RG-58, and not RG-85. Is it REALLY 85? (I never heard of
this number)

BTW this length 200 feet technically is out of spec, but usually works
if
you push it just a bit.

> >If the cable has to go outdoors, you should use something
nonconductive
> >(computers aren't lightning-safe), like fiber or radio.

This is 100% correct. A lot of it has to do with the fact that the
building grounds are not referenced together and in a lightning hit
on a building, one side of the wire can rise thousands of volts
above the other side, this will fry a lot of equipment. There exists
polyphasers to help with this.

> >>Anyway, does anyone have a few pci coax ethernet cards for
free/trade.

The old coax connector on these NICs is the BNC connector.
The consensis is that BNC stands for Bayonet Neill Concelman
(2 men's names) though other 'solutions' also exist, such as British
Naval Connector. AN on-going debate, this.

> >I know there are some ISA ones here that you're welcome to. No PCI,
> >AFAIK. If ISA's no good, you might try a second-hand computer store.
> >Microstar on S Dale Mabry used to have a decent selection.

I believe every NIC you will find today with a BNC connector fits an
ISA bus and runs at 10 Mbit/s signaling rate, not 10/100. This
BNC connector fits RG-58 and is the accepted physical media for
the 10Base2 protocol (2 = 200 meters, though really 185 m)

I have a bunch of SMC 8416 (83C795 chip) that work well
(EtherEZ) with BNC and RJ-45 but they are ISA bus.

> >>Also what are the correct terms for this (thicknet?) (N connecter?)

The N series connector is intended for 10Base5 cabling, which is the
coax that is approx. 1/2 inch in diameter. Applying an N connector
to this wire is generally done with a specialized AMP crimping tool
that crimps both the center pin and the braid collar. I've made a few
dozen of them in my lifetime. The taps are done with a "vampire tap"
requiring a clamp jig and a coring tool. THIS is "thicknet" and again
is rated for only 10 Mbit. (See: Cabletron ST-500 AUI transceiver).
Max cable length = 500 m.

Now there DOES exist a N connector with a narrow collar, intended for
RG-58 but then you need a between-series-adapter on each end to
convert the N connector to a BNC. These will cost more than new NICs,
or else you need to construct two pigtails. These are never
perfect and always cause impedance discontinuities which sometimes
are a problem. You need a TDR to find these problems. ( TDR == $6k)

My recollection is that in 1990 when this was the state of the art,
the AMP tool alone cost about $400. The handles were about
15 inches long. Once the ratcheting began there was no way to
release it unless you went through the whole crimp sequence.
If there was a misalignment in the connector pieces, tough.

All you guys who think that UTP was the beginning of networking,
ha ha. You don't know what you have missed out on.

Good luck with the coax. I would definitely NOT run it between
buildings.

Bob

PS - did I say to avoid running it between buildings ???

> >10Base2?
> >

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