ethernet cable? - (nf)

[rpw3 at fortune.UUCP]

#R:ukc:-412600:fortune:11600074:000:1838
fortune!rpw3    Mar 16 02:54:00 1984

Nothing's free. Triple-shielding plus double foil shielding plus silver
plating the center conductor does cost money.  For the budget minded, you can
use virtually any 50 ohm cable of an appropriate diameter to mate with your
Ethernet transceivers, BUT...  you lose some (or a lot) of:

	- maximum distance (due to increased attenuation)
	- maximum number of stations (attenuation and impedance variations)
	- EMI immunity (poorer shieding) [stuff getting IN]
	- RFI protection (shielding again) [stuff getting OUT]
	- long term mechanical stability (poorer quality insulation)
	- fire hazard protection (non-Teflon cable)
	- fire code approval (if non-Teflon and used in HVAC plenums)

For a small number (two dozen?) of stations with a short cable (100m ?)
under no fire code or electrical code restrictions and in an electrically
"clean" environment where you're not going to zap anybody's radio reception,
you can get away with standard RG-8/U cable (Radio Shack, among others).

Some companies are also using small diameter cable with their products
(notably 3-Com's "thin ethernet"). Again, degradation depends on the quality
of the cable. RG-58/U isn't half as good as RG-8/U, but there's an RG-1xx/U
(sorry, don't know the number) that is supposed to be relatively good.

But why gamble? Standard conforming cable is NOT that expensive, if you shop
around. You can buy it directly from Belden, Brand-Rex, and other fine cable
manufacturers for under $2.00/meter (retail is 3 times that). One hundred
meters is no more than ONE transceiver costs (roughly). By the time your net
is big enough to worry about the cost of the cable, you NEED that cable!
(Catch-22)

Rob Warnock

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