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I am moving to a house which has in-home wired network. The network runs like this, TV cable from outside comes to family room, I am supposed to connect cable modem and router at family room. There are 2 cables at family room, one has label "Up feed" which connect to upstairs office and the other "Down feed" to basement.

According to the previous owner, he had been using the upstairs office cable till the day he moved out which is just couple days ago and he used the basement cable couple months ago.

Yesterday I used a cable tester to test the cables, but neither up feed nor down feed show connection. I also did swap testing: testing up feed cable at family room with basement cable and down feed with upstairs office, same result, neither shows connection.

I then tested the tester on a short cable, it shows the connection is good. So the tester itself is functional.

So here are all I can think of:

1. The cables suddenly stop working. 

2. The tester cannot test long cable; it can only work at short one.

I hope it is #2. The tester I use is from Communication and model is S1007. I googled it but cannot find mentioning any length limit. I actually doubt it is the cable length - even though the cables are behind the walls, I do not know exactly how long they are, I think it is at most 100 feet or so.

I do not have cable company start the service yet, so I cannot test through accessing internet.

Do you have any suggestion if there are something else I can do here?

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I'm not familiar with the situation in your country, but when I read "TV cable" I assume, it's a coaxial (RG59) cable. Am I right, or is it indeed some kind of CAT.5 cable (multipole)? I'm asking, because with RG59 the (conducting) cross section is IMHO greater than in CAT.5 cables and length should matter much more in the latter case. Do you use a fresh battery with your tester? –  mpy May 1 '13 at 14:58

3 Answers 3

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Cheap cable testers often run on a 9V or a couple of 1.5V batteries.
They usually are not useful above about 5 to 10 meters (about 16 to 33 feet) as they simply don't have enough power to drive the test-signal across a longer cable.
You might be able to make it by inserting brand new, unused batteries.

They also just measure connection. That says nothing about the actual quality of the signal.

To measure quality you will need a very expensive tester that can generate test-signals in the proper frequency ranges. (I've got one rated for 10 Gb connections at the office. It costs about $200.000,-. A cheap one for 10/100 Mb connections can be had for around $400.)

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I assume these cables have a standard RJ45 8-position connectors on each end.

It is not likely that the cables just "stopped working".

The possibility I see is that for some (unknown) reason, the connectors are not wired in a standard configuration, which may require an adapter of some sort. For example, the cables could be wired as "Crossover" cables. I would suggest asking the previous owner if this is possible, or if they know anything that might explain it.

Also, as far as the cable tester, it could be that the batteres in the testers "active" module are low enough that it fails on a long cable run, but works on a short cable.

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All cabling specifications do have a length restriction, based primarily on their power and attenuation attributes. the max length for Cat5/5e/6 cabling is 100M, and yes, cable length faults are one of the things any decent cable tester would be able to detect. Good cable testers are very expensive things however (and I'm seeing one of your model on ebay for 5.50 USD), so the likelihood is that one for home-use really isn't very good, and may artificially increase the risk of user error.

be careful to make sure you really have both ends of the same cable. sometimes that's hard to do depending on your wiring scenario. Look for sources of interference along the cable run, including anything that uses or generates a significant amount of power, or uses magnets. you may have moved in some equipment that is causing an issue.

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