As for lightning, I live in the bullseye of "most struck" northern hemisphere
area, near Lakeland, Florida. The voltage from lightning is defined as a) Direct
Hit-
This has come out of the blue sky and there is not much hope for survival of
people
animals or equipment; b) Induced Voltage - Any and everything within about a five
mile radius of a lightning strike will see a voltage of over 1,000 volts per
meter.
That is what usually kills cattle in herds. Voltage induced in wiring in your
home door bell, telephone, and alarm wiring damages equipment, and "welds"
contacts.
We suspect induced voltage heightens the "galvanic" effect of dissimilar metals in
gutters, roof flashing, and plumbing, causing the various corrosion effects which
lead to failure. The underground conduit is like the underground AC wiring from
the power company, in that it suffers the same effects as overhead wiring, plus
attack by chemicals, corrosion, and animals (including the two legged variety).
You should "meg" both household grounds, and see if their grounds are the same.
A megger test is available from many of the electricians or the power company, but
could cost about $125. If you are very lucky in that both house meters are on the
facing sides of the houses, grounds could be close, but I would only trust the
experience and word of an expert, an electrician licensed fully in your state.
Here is why, Ohms law (1 ohm difference in the grounds at 1volt potential = 1amp
of
current) and you can stop the human heart with anything over about 20 milliamps.
So while you are hooking up the last ground connection or coax ferrel, and your
right hand is on the computer or ground and your left is on the ferrel or conduit,
1 amp or more may flow through your heart. Solution: AHA!! Fiberoptic light
modems! you can bury a fiber optic cable, and if it is not wired or armored, there
is no chance of induced voltage! The hardware costs are dropping, and it won't be
long before we'll be able to have 100mps thru put for about $65 per terminal.
William T Wilson wrote:
> I got this message, but I don't think it's really intended for me. :)
>
> ---------- Forwarded message ----------
> Date: Mon, 23 Mar 1998 16:39:42 -0600
> From: Paul F Almquist <[EMAIL PROTECTED]>
> To: William T Wilson <[EMAIL PROTECTED]>
> Subject: Re: Network
>
> On Sun, Mar 22, 1998 at 08:25:30PM -0500, William T Wilson wrote:
> > On Sun, 22 Mar 1998, CyberMan wrote:
> >
> > > What type of cable should I use for a network of 2 computers,
> > > considering that the distance between them is 100 meters max. I don't need
> >
> > There are a number of factors to take into consideration here.
> > Next, it is unsafe to string ethernet from one house to another without
> > taking precautions. Especially if you are planning on just letting it lay
> > in the yard. It could leak and short out in a storm, it could be eaten by
> > animals (gophers in particular love to chew on cabling), it could be run
> > over by a lawnmower. It could, as has been mentioned, be struck by
> > lightning. The only "safe" way to do this is to run the cable inside a
> > proper grounded conduit underground from one house to the next.
> >
> > Finally, many buildings (even those near to each other) will have
> > different ground electrical potentials, and having the ground potentials
> > too far off might make you wish you never plugged both computers into the
> > wire. You must test first as to whether the grounds are close enough (and
> > no, I don't know what "close enough" would be in such a case).
> >
> > In the USA, such an arrangement would probably be technically illegal due
> > to zoning laws. Your mileage may vary.
>
> a laser, microwave, radio, or infrared link would be much safer although
> more $$. consider ham radio - licensing required tho.
>
> the safety issues mentioned are real and should not be ignored.
> if this is a "just for fun" project it is probably not worth the $$.
>
> if it is essential check with a qualified networking professional and
> perhaps an electrical contractor.
>
> paul
>
> --
> /-------------------\\ //---------------------------/
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> / 620 W. Clairemont Ave \// Eau Claire, WI 54701 USA /
> /-----------------------------------------------------/
> / Paul F. Almquist, Instructor - DBMS,OS,Networking /
> / Computer Information Systems Dept HP-UX/Linux!! /
> / [EMAIL PROTECTED] Voice:715-833-6386 /
> / http://cis.chippewa.tec.wi.us/~almquipf /
> /-----------------------------------------------------/
>
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