[CQ-Contest] Network cables

[andrew]

In message <20011004212950.FPGT6803.imf05bis.bellsouth.net@[192.168.0.20
]>, Bill Coleman <aa4lr at arrl.net> writes
>On 9/24/01 7:53 AM, andrew at andrew at gi0nwg.freeserve.co.uk wrote:
>
>>With coax, if one of the *computers* dies, it does NOT impact the
>>network.  I can quite easily disconnect the BNC T-piece from the network
>>card of one of the machines (to simulate a dead machine) and the network
>>for the other machines continues normally.  If one of the coax cables
>>gets cut or damaged, that will severely impact the entire network as the
>>link is cut and the two sectors that we now have are not terminated
>>properly at each end.  
>
>Typically, it isn't the computer that dies, but the CONNECTIONS 
>surrounding the BNC T connector. I've seen lots of 10Base2 networks that 
>were really flaky. 

Quality BNC connections are fine in a network if you are not constantly
moving things around.  Probably the worst to use are those dreaded crimp
connections.  I'm not at all surprised that they fail regularly!
Properly installed soldered connections have given me no problems in
years (even on the lead that I connect and disconnect from my laptop on
a regular basis).  The only failure I've had is a terminator that died
unexpectedly.

>10BaseT or 100BaseT works a lot better. Plus, you 
>don't need to worry about proper termination.

I wouldn't say 10BaseT works any better than 10Base2, they both run at
10Mb/s and I would consider both to be equally reliable.  Naturally,
100BaseT will work better at 100Mb/s but most hams don't need that sort
of speed (a 10Mb/s easily runs a four computer gaming network so should
easily run a multi-computer contesting network).  However, with UTP
networks you need extra equipment (hubs) unless you are only connecting
two computers when you can use a cross-over lead.

>UTP is much easier to wire, 

I think it's debatable whether UTP is easier to wire.  All cables have
to go to a central point (the hub) and if the computers are well spaced
(as could be the case in a contest network) things start to get tricky.
You also have to buy the cables unless you have the special tools to put
the UTP ends on the cable.  Most hams have some RG58 and a soldering
iron and maybe even a couple of BNC connectors and can easily build that
themselves.

>and apparently has a great deal of rejection of common-mode RF 
>currents.

Properly installed coax or UTP networks should not have a problem with
RFI at amateur power levels (I've never had a problem with coax based
networks).  That's assuming proper installation procedures have been
used to keep RF in the shack to a sensible level.  That should be
standard operating practice anyway.

Andrew Williamson GI0NWG / AC6WI
Homepage = http://www.gi0nwg.freeserve.co.uk/

One of the ZL9CI gang
http://www.qsl.net/zl9ci/


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