Ethernet cable (Was: Sun3 valuations?)

[Al Kossow]

On 1/23/18 12:27 PM, Paul Koning via cctalk wrote:
> 

>> 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.
> 

He's holding up the wrong stuff if it's RG-8

Experimental Ethernet is 75 ohms.

see http://bitsavers.org/public_html/pdf/xerox/alto/ethernetEthernet_Transceiver_Electrical_Characteristics

Drive Voltage: +3 volts (Nominal) into  >> 37.5 ohms <<

There is a clue in the PARC Ethernet Blue and White about this where they mention they used CATV technology
(where the vampire taps come from ) but they don't actually say there that they used 75 Ohm cable, terminated at both ends.