-
Semper Vaporo
-
- Posts: 331
- Joined: Sat Oct 09, 2010 11:51 am
by Semper Vaporo » Wed Apr 29, 2020 6:55 am
Your continuity tester probably only tests for low resistance from one end to the other. This only indicates that DC (Direct Current) power can pass from one end to the other, but at the frequencies of the signals of a network there are things that can attenuate the AC (Alternating current) signal to the point of being too weak to be detected.
Ethernet cable is made of 3 pairs of wires where each pair is twisted at a different tightness along the length than the other pairs. This keeps the signals on each pair from interfering with the others (electro-magnetic coupling). So if the cable is not a genuine/purpose made CAT-5 cable (such as a home-made cable from just 6 ordinary wires) then that can be a major problem.
Does the longer cable have any tight coils in it to get excess length out of the way? Tight coils are like a "Choke" to AC signals.
Does it pass through or near large steel/iron or other conductive metal objects (such as steel wall studs or aluminium siding, or routed inside a metal conduit). This also can act as a choke.
Is it pinched tight where is passes through a wall? The loose twisting and loose jacket on the 3 twisted pairs of a CAT-5 cable are purposely there and a tight pinch can get the wires too close to each other and they will induce their signal on another pair, confusing the signal detectors at the ends of the cable.
If the cable is too long and has to be coiled up to keep the excess out of the way, loosen the coils up and spread them out as much as possible. (Loose cable laying on the floor should be spread out no tighter than, say, 3-ft diameter loops. Messy and sloppy looking, but necessary.)
Try to route the cable to be as far away as possible from metal objects, too. If it has to be in a conduit, use PVC (or other plastic) instead of a metal pipe.
If it has been pinched such that the 3 twisted pairs of wires are tightly against each other at some point, try to open up the pinch to spread the pairs out a bit. The pinch could also have split the insulation and caused a short from one wire to another, something you may not have checked with your continuity tester; that each wire is NOT shorted to any of the others.
Semper Vaporo,