32 Years of the Digest ... founded August 21, 1981
The Telecom Digest for May 25, 2014
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Date: Fri, 23 May 2014 21:49:34 -0500 From: Frank Stearns <firstname.lastname@example.org> To: email@example.com. Subject: Re: Cable selection for Overland Ringdown System Message-ID: <nZWdnWq-cOYjlR3OnZ2dnUVZ_gednZ2d@posted.palinacquisition> Thad Floryan <firstname.lastname@example.org> writes: >On 5/21/2014 12:01 PM, Frank Stearns wrote: >> I'm looking to put phones between two households with a ringdown box; the houses are >> approximately 700 feet apart. (We already have radio links for voice and data; but I >> also want a hard-wired back up.) >> >> Looking for practical advice on cable selection. This wire will go overland, though >> it is feasible to put it under 3-6" of soil in a quick little trench most of the >> way, but parts perhaps could be exposed, if I found suitable cable. >> >> I was thinking of some sort of armored CAT5; then I'd have four pairs. But perhaps >> there's a better 2 pair cable for this application. (I do want at least two pair; >> with one pair as a spare. The cat5 was interesting because I'd have two additionl >> pairs for some other future use.) In those exposed sections we'd need something that >> the chipmunks, squirrels, rabbits, and other critters would not find tasty. >> >> Cable suggestions welcome, >Hi Frank, >Friendly advice: fiber, for electrical safety between different >outdoor structures/homes. There may be local codes in your area >requiring fiber as there are here (Silicon Valley). I recall when >HP was establishing data paths between its buildings along Page Mill >Road in Palo Alto that fiber was the only correct and legal solution. >This article seems to be a good starting point especially for the >types of gear at each end of the fiber: > > http://en.wikipedia.org/wiki/Last_mile > >Googling "fiber endpoint equipment" [without the quotes] will also >list the manufacturers and types of gear for fiber endpoints that >"should" be suitable for your application. >Safety is the operative word here. One of my hobbies is astronomy >and many friends have attempted to run CAT5/CAT6 between their homes >and their outdoor observatories and the horror stories are legion >with ground loops, lightning strikes, and more. Thanks, Thad. I was planning on putting some sort of lightening arrestor on both ends; the grounding subject is interesting. Assuming there's conductive armor on the cable, should that be tied to ground stakes at both ends just prior to entering the buildings? What if there is no conductive shielding? In terms of the lightening issue, what's the main risk? Cable is on the ground (or just below the surface), and there are trees and other (hopefully better) "targets" elsewhere nearby, including a 115KV transmission line about 150' from one of the houses. Those lines are a good 30-40 feet off the ground. Fiber is an interesting idea, but the concept here is to keep this whole thing as super simple as possible (and hopefully less prone to failure) -- the whole install would consist of the ringdown box, cable, and an old 500 series desk set on each end. Once again, thanks in advance for all the sage advice. And if it were feasible, I'd love to run buried conduit but that's not possible for a number of reasons... Frank [moderator pro tem's note: An old rule of thumb for copper wiring is that any loop that leaves the building needs lightning protection. If it is entirely underground, cheap carbon protectors will do. If it goes above ground, stick to the better gas tubes. Protectors need proper grounding.] -- .
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