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Author Topic: Resistance values along phone cable route in my house  (Read 951 times)

hake

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Resistance values along phone cable route in my house
« on: January 08, 2018, 11:21:20 AM »

I am troubleshooting my internal phone installation.  The cabling follows a single route through the house via three intermediate BT phone socket boxes.  The resistance of each of the pair of wires is 6 ohms from end to end (no bell wire is used).  Is this satisfactory?

Thank you.
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4candles

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Re: Resistance values along phone cable route in my house
« Reply #1 on: January 08, 2018, 04:43:35 PM »

With perfect terminations and accurate measurement, that equates to a bit over 60 metres of genuine CW1308.
« Last Edit: January 08, 2018, 04:46:31 PM by 4candles »
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Weaver

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Re: Resistance values along phone cable route in my house
« Reply #2 on: January 08, 2018, 05:00:51 PM »

If you've used decent quality twisted pair such as CW1308 or better and kept it away from mains and other sources of interference then there shouldn't be much of a problem. It's attenuation at various frequencies that matters, not dc resistance, but interference pickup is really what it is all about.

I have zero metres of internal wiring, I got BT to do a 'change point of entry' to move the line to exactly where I wanted it, so each line (I have three) comes straight into the house right to my the modem, and then any extra distance that needs to be covered is handled by ethernet which is 100% perfect.

If you are desperate to get the best performance, then BT ‘change point of entry’ and zero internal wiring is the way to go. This means moving the point where the cable first comes into the house to be exactly where you want it, and that will be where BT will park the master socket for you, but for best results this really must have a (hopefully minimal) run outside the house not inside. Then for you to get the benefit you absolutely have to move your modem to where the master socket is, which is hopefully now at the first point at which the cable enters the house. My reasoning is that all house-internal DSL signal wiring is potentially suspect because of all the interference sources in a house from mains and mains-powered equipment. You ask the company that you pay your line rental to, your phone service provider (if you have one), to organise a BT engineer if you want.
 
If running cable through the house is a pain use wireless as that is 100% perfect (because of error correction and fast layer-internal retransmissions), provided of course that the signal is kept reasonably strong.

It is not necessary to have the source of your wireless network parked at the same place as where your DSL modem meets the incoming line. If you minimise internal wiring for DSL signal, you can have a wireless access point (base-station-transmitter which controls the wireless lan) on a long ethernet cable connected to your router and park it in a different place for better signal spread, such as in the centre of the house whereas your modem/router might be on an outside wall for shortest dsl signal run. This is all more inconvenience and nuisance running fragile ethernet cable  though. This is how my wireless works. Modems are by a window on an outside wall upstairs, there is a pair of long ethernet cables from the router to two wireless access points in the exact centre of the house, one on each floor, to give a wide spread of signal. So wireless location for best signal reach doesn't have to be the tail that wags the dsl quality dog.

It all depends on how obsessive you are or aren't about dsl performance (more speed)and reliability, versus inconvenience - relocating kit, possibly booking bt - and a small expense - cost of bt poss, cost of a WAP poss.

I never my case I was extremely pleased with the results which were stunning, speeds went through the roof.

Don't hesitate to come back with any questions?
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hake

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Re: Resistance values along phone cable route in my house
« Reply #3 on: January 08, 2018, 07:34:47 PM »

The resistance could be accounted for by the four intermediate sockets with punch-down connections.  The phone works fine now so I guess that the ohms are not too high.  Much of the cable was installed by a BT person in 1989 and subsequently extended by another BT person.  The route of the cable does avoid proximity to interference sources.  The ADSL2+ signal uses a separate screened Cat5E cable with 2 twisted pairs which runs in parallel for much of the route taken by the telephone extension cable.

Thank you for those several paragraphs which make helpful and interesting reading.

Additional meanderings: -
Hmmmmm. I forgot the length of cable I required to join the opposite ends for the continuity check.  I didn't take that into account when quoting the measured resistance.  I guess that the actual resistance is approximately 4 ohms.  That'll do me.
« Last Edit: January 08, 2018, 09:40:59 PM by hake »
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4candles

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Re: Resistance values along phone cable route in my house
« Reply #4 on: January 13, 2018, 12:32:38 PM »


Hmmmmm. I forgot the length of cable I required to join the opposite ends for the continuity check.


Ah, OK. I kind of assumed you'd allowed for that, or had measured from one end with the far end looped and halved the reading.
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