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I want to know what cable I should be using to connect my demarc to my DSL modem. When I plug in my DSL modem in the utility room (which is about 20' of wire from the demarc) I get a pathetic 4Mbps download rate (I'm told the telco's hardware is very old in my neighbourhood). When I test the modem by plugging it directly into the demarc, it jumps to 6Mbps. I want to connect my modem closer to the demarc (but I can't plug it into the demarc, because it's outside) and maybe use a different cable, but what kind of cable should I use? I heard in one place that CAT-5 is better than phone cable, but I've also heard there wouldn't be an improvement.

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    \$\begingroup\$ Why is the run from the external demarcation to the internal breakout 20 feet? \$\endgroup\$ – Passerby Feb 7 '15 at 19:08
  • \$\begingroup\$ Can you put the DSL modem in the utility room? Then run cat 5 from the modem to wherever it is needed? \$\endgroup\$ – mkeith Feb 7 '15 at 21:19
  • \$\begingroup\$ @Passerby Because the demarc is outside, at ground level, near the front of the garage and the utility room is behind the garage in the basement. And because the cable goes through the garage's ceiling, 20' is probably understated. \$\endgroup\$ – PenguinLust Feb 7 '15 at 22:22
  • \$\begingroup\$ @mkeith I can, but the big question is: is CAT-5 the best cable to use? Beyond that, I'm wondering how much better I'd be with a shorter cable, if it's a better cable. \$\endgroup\$ – PenguinLust Feb 7 '15 at 22:25
  • \$\begingroup\$ Sorry, I misread the question. \$\endgroup\$ – mkeith Feb 7 '15 at 23:35
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Use a twisted pair wire instead of the parallel satin-coat wire normally used to connect telephones to wall-jacks. You may have to make your own - this is easy if you have the tools and connectors.

I purchase a lot of 3-pair telco cable - the wire guys often refer to it as "Cat-3" wire. This is 3 twisted pairs inside a pvc jacket. However, one pair of Cat-5 should work well as well.

The reason I would use Cat-3 cable over Cat-5 is that the number of twists per foot for Cat-3 is similar to the number of twists per foot of the cable between your premises and the telco central office. Cat-5 has many more twists per foot than Cat-3.

Regardless, this is quick and easy for you to test.

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  • \$\begingroup\$ So you're saying that the cable I'm using is probably not twisted pair (that stupid electrician! He knew I was doing this for DSL!) In that case, I'm wondering if I'd be just as well leaving the modem in the utility room and running the Cat-3 all the way from the demarc. Either way, I'm going to be running a fair bit of cable from the demarc to the utility room: either Cat-3 all the way from the demarc to the utility room or Cat-5 from near the demarc to the utility room. \$\endgroup\$ – PenguinLust Feb 7 '15 at 22:29
  • \$\begingroup\$ My opinion, for what it's worth, would be to mount the modem near the demarc block and run Cat-5 cable from the modem to your switch or whatever. The only reason not to do this is if the modem is also your router / wireless access point. In that case, place it wherever gives you the best wireless coverage and use either Cat-5 or Cat-3 to get from the modem to the demarc. \$\endgroup\$ – Dwayne Reid Feb 7 '15 at 23:01
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    \$\begingroup\$ Changing twists per meter/foot won't impact quality (though more is better, so I'd use Cat5) - you may be thinking of impedance. I've usually heard of Cat3 as being two-pair... @PenguinLust, what does the cable look like now? Make sure the conductors are actually the same pair, and he hasn't just grabbed two random wires (from different pairs) and used them. \$\endgroup\$ – Someone Somewhere Jun 1 '16 at 11:09

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