kwe@bu-cs.BU.EDU (kwe@bu-it.bu.edu (Kent W. England)) (01/18/89)
>In article <13433@bellcore.bellcore.com>, Phil R. Karn writes: >>> [when I said] >>> However, many >>>people have blissfully installed thick between buildings (including >>>me) without any problem whatsoever. >> Your bliss may end the next time you have a nearby lightning strike. Perhaps it was irresponsible of me not to say something about lightning risk, but it hasn't ever come up in my environment. On our urban campus it can be difficult to tell when the address has changed, since many of the buildings are all run together. When a cable crosses a street, it is in a steel conduit in a concrete jacket buried in the earth. I don't think lightning is a real risk in that situation. The telephone company puts fuses in a main distribution frame in our garage and then runs cable 300 feet down the street thru a string of buildings to its final destination. They don't seem to worry about induced transients on copper pairs. All without benefit of conduit except to cross the street. My main worry in running thick Ethernet cable between buildings is differences in ground potential due to the way the electric power feeds are distributed and grounded. If an Ethernet crosses substation boundaries, then there is some risk of ground potential differences and the thick cable won't work. But for the folks watching this on TV, "Don't try this at home. These are trained professionals paid to make the stupid mistakes for you." :-) In other words, you should pay a little more for the requisite interface hardware (the fiber optic gear) and use fiber between buildings. That is the sort of conservative advice I should be giving and not making comments like "installing thick cable without any problem whatsoever." That should set the record straight. Kent England, Boston University
eggers@ndcheg.cheg.nd.edu (Mark Eggers) (01/18/89)
Well folks,
The College of Science put some coax between buildings here.
Ran the cable through steam tunnels (albeit with a lot of other
cable). At first they didn't even ground one end. Needless to
say, DEC got tired of replacing transceivers, Ethernet boards, etc.
every time we had a good thunderstorm. We get quite a few thunderstorms
since we are in the 'lake effect' weather area of northern Indiana.
Even after the coax was properly grounded, they got zapped a few
times. There is now a standing order (as much as it can be on a
university campus) - only fiber between buildings. It's nice to
be able to go to sleep on Spring and Fall nights, knowing that
the phone will probably not wake you up to report a network
down.
/mde/