[UK-CONTEST] UK-Contest Digest, Vol 87, Issue 28

[John Wilson]

Fascinating, this was obviously a bodge conceived by an amateur that has 
been industrialised!  I guess, like thin ethernet, the impedance of the 
tap is high so it doesn't  have too much effect on the signal but if 
this the case then why bother with the half wavelength markers?

John G3UUT

David Ferrington, M0XDF wrote:
> Wow, haven't seen them or used one since the early 80's.
>
> The half wave point on the freq. used for thick net is approx. 1m, so the cable is made with a black ring at the half wave point all along it's length. You must put the end connectors on at the marker (I don't remember what type they are, N I think).  Then, when you want to tap into the cable to connect an Ethernet device, you use a special Ethernet device with has a block with a channel and an insulated pin in the centre. You use a tool to make a hole in the the sheath, through the braid, then through the dielectric. each hole getting progressively smaller so the brad does not short to the inner. Then you clamp the block over the cable, the pin goes into the inner and a ring of pins goes into the braid. An Ethernet 'D' type connector then connects a multi-core cable from the block to an Ethernet card in the computer.
>
> That's a vampire trap!
>
> :-)
>
> Unlike thinnet, where to use BNC and T pieces - don't know if you could use traps with that.
>
>