Ethernet cable (Was: Sun3 valuations?)

Brent Hilpert bhilpert at
Wed Jan 24 15:05:55 CST 2018

On 2018-Jan-23, at 12:27 PM, Paul Koning via cctalk wrote:
> The Ethernet spec says that the cable OD is in the range .365 to .415 inch, which is 9.27 to 10.54 mm.  The nominal OD of RG-8/U is .405 inches, or 10.28 mm, which is within spec for Ethernet cable.
> One place where the two cable specs differ is in the velocity factor, 0.66 for RG-8/U and 0.77 for Ethernet cable.  That relates to the dielectric -- solid polyethylene for RG-8/U and foamed material (unspecified) for Ethernet.  Also, Ethernet requires a solid inner conductor (for the tap) while RG-8/U may come stranded.  (Maybe only in some variants, I'm not sure.)  And there are the stripes, of course, but those have no electrical significance.  You can use a tape measure if you don't have the stripes.

I was attempting some calculations to see if I could derive the 2.5M transceiver spacing and was wondering what the velocity factor for the cable was, as it should affect the transceiver spacing in theory.

I haven't seen any pictures during this thread of the transceivers we used with the 10MB yellow hose - heavy gauge metal boxes about 3" * 4" * 1" with N connectors. I remember piling up the 3 ft diameter loops of yellow coax in the machine room where you had a bunch of machines together and didn't need the cable lengths between them, until the DEC DELNI (ethernet AUI hub) cleaned up that mess.

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