> On Jan 23, 2018, at 3:19 PM, Noel Chiappa via cctalk <cctalk@classiccmp.org>
> wrote:
>
>> From: Grant Taylor
>
>> I can fairly clearly see the RG-8/U on the side of the cable that David
>> is holding ... Sure, there was probably a better alternative that came
>> along after, with better shielding and marking bands.
>
> You keep mixing up the 3 Mbit and 10 Mbit. _They were not the same_. (I
> _really_ need to retake those photos with a ruler in them...)
>
> The stuff with better shield, marking bands, etc is 10 Mb; it's about 1.05cm
> in diagmeter. The black stuff (the stuff Dave is holding in the video) is 3Mb;
> the piece I have is .95 cm.
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.
paul
