On 02/02/2018 12:35, AnthonyL wrote:
On Thu, 01 Feb 2018 14:46:46 +0000, T i m wrote:


I ran some Thin Ethernet in Heathrow T4 and they needed a specific
(Belden) cable (I think) that had a secondary foil screen because of
the high levels of RF / Radar that was about. Had I not used the
'right cable' I could easily say that 'Thin Ethernet sucked' when it
was clearly the result of the location. The fully loaded 8 port Thin
Ethernet repeater I installed at a previous job never had any issues
at all using standard RG-58C/U.


We had no end of intermittent problems with a repeater especially on
one or two segments.

Had to get specialists in, with fancy equipment and they were
scratching their heads. For some reason I happened to measure the
shielded earth to a socket earth - there were volts there!!

Yep the offices was two houses, joined together, the front being on
one transformer and phase and the back being on a different
transformer and phase with earth differences. Sparky redid the fuse
boxes/earths etc and no more problems. A long time ago but I don't
think the two supplies into one property was a permissable arrangement
for similar reasons to the problems we encountered.





You are only supposed to have one earth on a thin/thick ethernet cable.
The actual signal bit is via isolating transformers so you could have
1000V on the cable and it would make no difference.

The same is true for "CAT" wiring except you don't need a screen or
earth except to stop your equipment radiating cr@p. With screened cables
they should only have an electrical earth at one end and maybe a
capacitive earth at the other. They should not connect the electrical or
the mains earth together to avoid problems like earth potential differences.
You need several mm2 cable if you want to connect earths together not a
networking cable. We used 70 mm2 earths for the project we did with BBC
labs which I thought was a bit OTT but that's what the maths said.