24 Jan
2018
24 Jan
'18
4:05 p.m.
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.