All twisted pair ethernet wiring
schemes rely on the twists for noise
immunity. Using connectors or splicing schemes not rated at least as highly (in CATegory terms) as your wire will degrade the signal and noise
immunity to some degree. While shielded twisted pair is usually specified to reduce susceptibility to outside RF interference
, when I was in the marine electronics
industry we had a problem with radiation from ethernet into VHF
radios. I would guess, though, that a small gap in shielding (if your coupling solution doesn't fully shield the connection) won't have an impact.
Any insulation displacement
connector you use needs to be designed for the wire you're using. At least RJ45 connectors are specified for solid or stranded (or sometimes both) wire. The shape of the contact that pierces the insulation
is different for the two, and using the wrong one can cause intermittent problems which manifest themselves as either bit errors or degraded speed.
The junction box mentioned earlier looks to be a good choice if you're not going to be disconnecting this cable frequently. The terminal design allows you to maintain the twists just like a typical punched down RJ45 jack. They also have a shielded variant
if you want to maintain the shielding end-to-end, and it's surprisingly cheaper!