[HamWAN PSDR] PSDR Digest, Vol 88, Issue 2

[Colin Stanners]

On Tue, Jun 2, 2020 at 2:00 PM <psdr-request at hamwan.org> wrote:

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> Today's Topics:
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>    1. Re: VOTE: Baldi LAN expansion and Rattlesnake link (Bart Kus)
>    2. Re: VOTE: Baldi LAN expansion and Rattlesnake link (Rob Salsgiver)
>    3. Re: VOTE: Baldi LAN expansion and Rattlesnake link (Doug Kingston)
>    4. Re: VOTE: Baldi LAN expansion and Rattlesnake link
>       (Nigel Vander Houwen)
>    5. Re: VOTE: Baldi LAN expansion and Rattlesnake link
>       (Dale Skyllingstad)
>    6. Re: PSDR Digest, Vol 88, Issue 1 (Colin Stanners)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 1 Jun 2020 12:01:25 -0700
> From: Bart Kus <me at bartk.us>
> To: Puget Sound Data Ring <psdr at hamwan.org>, Tom Hayward <tom at tomh.us>
> Subject: Re: [HamWAN PSDR] VOTE: Baldi LAN expansion and Rattlesnake
>         link
> Message-ID: <855d86f1-e969-74ae-77c1-3f43827ce640 at bartk.us>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> I'm not sure what there is in there.  Heard vague recollection of a pair
> of CAT5s in there, but not with any certainty.  This is why we need to
> go survey the place.  I would expect their grounds to be tied given the
> power system changes, and the conduit to be bonded. Worst case though we
> can omit the shield as CAT5 Ethernet is only magnetically coupled (has
> isolation transformers) and uses differential signaling.
>
> I'm kind of hesitant to introduce fiber to HamWAN where it's not
> absolutely necessary.  We have enough problems with proper RJ45
> terminations, never mind asking people to re-terminate fiber if
> something breaks.
>
> Copper Ethernet may be theoretically isolated / only magnetically coupled,
but I've seen many cases where ground potential difference of a few volts
(e.g. customer PC plugged into an ungrounded outlet) would cause lots of
problems over the Ethernet line, sometimes variable and difficult to trace.
Same for heavy RF nearby. If cat5 cable is already there it's worth
testing, but even if it tests well issues may occur over time, or you may
find Ethernet ports fried after a lightning storm.

Also be careful of ground loops when interconnecting buildings - one
broadcast tech told me of a big tower NE of Winnipeg where the ground cable
between equipment buildings was so hot it would melt snow due to the ground
taking a path that it shouldn't have.

The last paragraph is a great point. For setups I often run dual fiber
lines and only use one of them, so that there is a spare. If something cuts
your conduit and all the fiber lines, you have a bigger problem.
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