5 ms·

Here at NASA Goddard, old wiring is often never removed. In the cable trays in the hall outside my office is some ancient coaxial Ethernet cable. At one point,

Here at NASA Goddard, old wiring is often never removed. In the cable trays in the hall outside my office is some ancient coaxial Ethernet cable. At one point, there is a tap and one of the standard cables that went from the tap to a workstation. I keep thinking I should grab the tap and squirrel it away as a historical artifact.

mhalle 9y ago
Vampire tap. You had to place them at marked locations on the coax because of signal reflections.
- jacquesm 9y ago
  And because at that point the shield wires were spaced further apart so as not to short out the connection.
  - jonsen 9y ago
    Really? Sounds like a major complication to the cable manufacturing process. Wouldn't all those holes in the shielding hose degrade cable specs? All for not having to drill a hole for the eventual connecting tap.
    - jacquesm 9y ago
      It is not that big a deal actually, either you drill a hole with a special tool and then align the tap with the center of the hole or, on some cable you align the tap with a special dot mark on the cable where the shield has been moved aside a couple of mm. It is a convenience at the slight cost of some loss. Far faster to connect to than drilling holes in insulation using yet another tool. It really adds up if you have to make a lot of drops on a cable. If there is one thing I am happy about then about then it is that we no longer have coax networks. Nightmare stuff. Flaky connections and weird voodoo problems.
      - teh_klev 9y ago
        > If there is one thing I am happy about then about then it is that we no longer have coax networks I used to install 10BASE2 and 10BASE5 infrastructure back in the late 80's and into the late 90's. I hated having to install 10BASE5 vampire taps for fear of completely buggering up what were already creaky 10BASE5 networks where the 2.5m rule was widely flaunted by on-site staff. I remember a job at a factory in Manchester where I had to install a bunch of kit on a 10BASE2 installation. The customer insisted on running their own cables and swore blind they knew what they were doing and had done their previous install etc. When I arrived I discovered the coax had been installed in a star config :/ Yes good riddance to coax bus networks.
    - mhalle 9y ago
      In general, there weren't "all those holes" because most sites didn't have that many networked computers. This was the pre-PC era. 10BASE5 could only have taps every 2.5 meters. https://en.wikipedia.org/wiki/10BASE5 https://en.wikipedia.org/wiki/10BASE5
walshemj 9y ago
probably a decent amount of copper in those old thicknet cables
technofiend 9y ago
NASA JSC were still using Altos systems for word processing in the early 90s when I was there, complete with a dancing Snoopy screen saver. I wouldn't play with the cables because there could still be a legacy server somewhere humming away in the forlorn hope someone will need to print a station manual.

mhalle 9y ago

Vampire tap. You had to place them at marked locations on the coax because of signal reflections.

jacquesm 9y ago
And because at that point the shield wires were spaced further apart so as not to short out the connection.
- jonsen 9y ago
  Really? Sounds like a major complication to the cable manufacturing process. Wouldn't all those holes in the shielding hose degrade cable specs? All for not having to drill a hole for the eventual connecting tap.
  - jacquesm 9y ago
    It is not that big a deal actually, either you drill a hole with a special tool and then align the tap with the center of the hole or, on some cable you align the tap with a special dot mark on the cable where the shield has been moved aside a couple of mm. It is a convenience at the slight cost of some loss. Far faster to connect to than drilling holes in insulation using yet another tool. It really adds up if you have to make a lot of drops on a cable. If there is one thing I am happy about then about then it is that we no longer have coax networks. Nightmare stuff. Flaky connections and weird voodoo problems.
    - teh_klev 9y ago
      > If there is one thing I am happy about then about then it is that we no longer have coax networks I used to install 10BASE2 and 10BASE5 infrastructure back in the late 80's and into the late 90's. I hated having to install 10BASE5 vampire taps for fear of completely buggering up what were already creaky 10BASE5 networks where the 2.5m rule was widely flaunted by on-site staff. I remember a job at a factory in Manchester where I had to install a bunch of kit on a 10BASE2 installation. The customer insisted on running their own cables and swore blind they knew what they were doing and had done their previous install etc. When I arrived I discovered the coax had been installed in a star config :/ Yes good riddance to coax bus networks.
  - mhalle 9y ago
    In general, there weren't "all those holes" because most sites didn't have that many networked computers. This was the pre-PC era. 10BASE5 could only have taps every 2.5 meters. https://en.wikipedia.org/wiki/10BASE5 https://en.wikipedia.org/wiki/10BASE5

walshemj 9y ago

probably a decent amount of copper in those old thicknet cables

technofiend 9y ago

NASA JSC were still using Altos systems for word processing in the early 90s when I was there, complete with a dancing Snoopy screen saver. I wouldn't play with the cables because there could still be a legacy server somewhere humming away in the forlorn hope someone will need to print a station manual.