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How do I test a twisted pair run for signal quality

Posted on 2004-08-14
Medium Priority
Last Modified: 2013-12-14
I am renting a house in Phuket, Thailand for a year or two.  The telephone system here is about what it was like in the USA 5 years ago.  For example, I am sending this message via a regular old dial-up modem connection that's getting 30 to 38 kilobits per second.

There's a local outfit that will sell me Internet bandwidth (256 kilobits per sec with peaks up to about 800 kbits --- that's all the way to a router in the US).  I hope to use this for both data and VoIP. They will get the Telecom Org of Thailand (TOT) to run copper to a pole outside the house (which is in a small compound).

We have found some unused twisted pair that can be jumped all the way from the pole to an unused  RJ45 (currently RJ11 of course) faceplate in the room where I need it.  I would say this cable is 5 years old, it is certainly not cat 5 (in fact it is the old-fashioned 4-wire stuff --- red, green, and (unused yellow and black).  The guy who installed it obviously knew what he was doing --- the TP is nicely dressed, tied, and labelled, and the 66 block is nice and tidy. The cable distance from pole to faceplate is about 45 yards, with two jump points.

Before I spend too much on this, I want to test signal quality the existing twisted pair from the pole to the faceplate.  I believe I need some kind of signal generator at one end, and a Dbmeter on the other, but I'm not sure. Here are my specific questions:

1. What equipment do I really need for this?  Any suggestions as to supplier and price (I can have it bought in the USA and Fedexed here)?

2. Any tricks or suggestions for using it?

3. Most important: how much dB loss is too much?
Question by:cliffbamford
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LVL 40

Assisted Solution

Fatal_Exception earned 1200 total points
ID: 11803839
I use meters from Fluke for all my testing, but beware, these are not cheap.  Since I am visiting the in the country right now, I do no have access to my test epuipment, and it may be a week till I am back, so hopefully another expert will have a model for you here.

If you are stringing the cable aerially, the biggest problem you will face is what you will be suspending it from.  Telco's and Cable Co's use what we refer to as Strand to support their cables.  (See my profile, I used to build these).  A 45 yard stretch will put a lot of tension on the cable, and the wire will basically be pulled tight and expand, loosing the twist, and you will big time attentuation (dB loss) if you do not use something to hold the wire up with.

The dB loss in standard installs is a -15 limit, but again, that will be determined by the existing signal strength, so I am hesitant to say what will work in your specific circumstances.  If the TOT guarantees the signal strength, then I would get with their techs to determine and help you with the attentuation issues.  They should be able to advise you here.

Best of luck and will ck back when I get a chance to see if others have stepped up and offered any advice....  


Author Comment

ID: 11804249
Thanks, FE --- the problem is, I don't want to have TOT string any cable on poles until I  know if the existing 4-wire from the pole to the faceplate (45 yards of cable run) is clean enough to carry 250 kbits of ADSL.   The service delivered to the telephone pole outside the house isn't the problem --- those guys pretty well know what they're doing, and will use the right kit on that part.

In any event, thanks for replying --- it's encouraging to know that somebody even read my original question.   Enjoy your couintry trip and I hope to hear more upon your return.

LVL 12

Accepted Solution

public earned 300 total points
ID: 11805009
45 yard drop directly to the modem with no other taps has negligible impact on dsl signals. Total run from the CO should not be more than 19000 ft and less tha 60 dB attenuation.
Make sure you install a splitter if you plan to use other phones on the line.
When the service is activated you can see the attenuation and the sync speed in the modem status page.
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LVL 40

Expert Comment

ID: 11811114
Should have asked it this was DSL in the beginning...  Never know what the Asian countries are delivering nowadays.  In this regard, public pretty much spelled it out, as the attentuation will be neglible for a 45 yard run.  You can still use a meter to test it with, just cut the amount you need off a spool and test it by itself, but you will find it will work just fine.

Good luck, and thanks to public for stepping in while I was out of town...  :)

LVL 40

Expert Comment

ID: 12076644
I think we pretty much answered the question here...


Author Comment

ID: 12081670
Sorry I wasn't paying attentio to thge way this worked ----- thanks to FE and public ---- CB
LVL 40

Expert Comment

ID: 12083152
And we thank you..!!


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