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Author Topic: My cables  (Read 19661 times)

konrado5

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Re: My cables
« Reply #15 on: September 10, 2014, 03:41:09 PM »

Quote from: burakkucat
I would imagine it entirely depends upon the transceiver circuitry. In other words, how well the induced 50 Hz common-mode "hum" is rejected by the differential input stage of the receiver.
Quote from: burakkucat
Would you expect to see it? One "tone" of an xDSL service is 4.3125 kHz wide. The mains frequency is 50 Hz. Think about the scale of those frequencies, it is 86.25 to 1 . . . (Would I expect to see anything? No.
1. Why would you expect to 50 Hz common-mode "hum" affect the ADSL service? What way, if it would be not noticable in QLN? Why does switching off can be heared in the AM radio on the significantly higher frequiences if mains frequency is 50 Hz.
Quote from: burakkucat
Just as one would expect to see the same DC resistance across the same length of the two legs of a cable pair, so one would expect to see similar AC resistance -- impedance -- for the two legs. (Along with other properties.) Good AC balance for two legs of a cable pair is just a way of ensuring that those two wires behave similarly. Remember an xDSL circuit operates in differential mode, so it is the difference in the signal carried on the two wires that is important. Having two mismatched wires (poor AC balance, non-similar DC resistance, etc) will result in the wanted signal being distorted at the receiver.
2. How can I check AC balance? Is it noticable in Hlog, QLN, SNR margin graph?

Best regards
konrado5
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burakkucat

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Re: My cables
« Reply #16 on: September 10, 2014, 04:41:38 PM »

Quote
2. How can I check AC balance? Is it noticable in Hlog, QLN, SNR margin graph?

No, the graphs will not provide any information. Hand-held testers, such as a JDSU HST-3000c or an Exfo AXS-200/635, will have the means to qualify a circuit. They have an option to perform a Pair Quality Test (PQT).

Quote
1. Why would you expect to 50 Hz common-mode "hum" affect the ADSL service? What way, if it would be not noticable in QLN?

An induced longitudinal signal (common mode signal) could bias the differential input circuit and distort its operation, to the detriment of the wanted differential signal, for example. A well designed and optimality constructed differential circuit should be capable of rejecting a longitudinal (common mode) signal. But no circuit will ever be perfect. So it would be sensible to ensure that any influence of an unwanted signal is minimised.

Quote
Why does switching off can be heared in the AM radio on the significantly higher frequiences if mains frequency is 50 Hz.

It is due to the spark that is generated when the current being drawn by the load is interrupted by the act of switching off. The original radio transmitters were spark devices -- they radiated significant energy across the entire radio spectrum. There were true broadband signal generators, without any means of real tuning the signal to a specific frequency. (Perhaps you will find it interesting to read about Marconi's original radio experiments and his very high voltage spark transmitters.)
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konrado5

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Re: My cables
« Reply #17 on: September 10, 2014, 05:13:49 PM »

Quote from: burakkucat
No, the graphs will not provide any information. Hand-held testers, such as a JDSU HST-3000c or an Exfo AXS-200/635, will have the means to qualify a circuit. They have an option to perform a Pair Quality Test (PQT).
1. How is it possible the graph will not provide any information if bad balance affect quality of servie? Is it not raise attenuation? Is it not raise noise level? SNR on every distinct tone is affected only on power output of this tone, attenuation of this tone and noise of this tone.

Quote from: burakkucat
n induced longitudinal signal (common mode signal) could bias the differential input circuit and distort its operation, to the detriment of the wanted differential signal, for example.
2. What would be accurate affect? Higher QLN, higher attenuation, signal reflections?

3. Does spark cause little (1-2) CRC errors on fast path if someone has phone lines far away from mains circuit? I suspect it also cause CRC error because it is noticable in AM radio regardless where I put radio.

Quote from: burakkucat
Quote from: konrado5
Has internal CW1308 cable good AC balance?
Yes, of course. It is a stipulation of that specification.
4. Can CW1308 damage cause bad AC balance? Can loose joint cause bad AC balance?

5. Why does spark does not cause SNR lowering? It only causes errors.

Best regards
konrado5
« Last Edit: September 10, 2014, 05:16:05 PM by konrado5 »
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konrado5

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Re: My cables
« Reply #18 on: September 11, 2014, 02:20:16 PM »

When I do spark I has following BER at SNR margin 1.1 dB (1 CRC error).

Test Time (sec):       20
Total Transferred Bits:       319426560
Total Error Bits:       744
Error Ratio:       2.33e-06
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boost

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Re: My cables
« Reply #19 on: September 11, 2014, 04:36:27 PM »

konrad... get a JDSU~ please :D
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konrado5

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Re: My cables
« Reply #20 on: September 11, 2014, 04:57:43 PM »

Unfortunately JDSU is very and very expensive. I'd like to test  my line accurately. Perhaps modem firmware modify would be helpful.

Best regards
konrado5
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burakkucat

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Re: My cables
« Reply #21 on: September 11, 2014, 06:01:44 PM »

Just a quick note from The Cattery to say that I have posted everything, of which I can think, that relates to the wiring shown in the pictures.

If that wiring was in my home and I was not happy with my broadband service performance, I would rewire the circuit from the circular connection box to a convenient location for the socket. I would use a new length of the appropriate specification cable (CW1308 or better) and would probably fit a new socket, rather than reusing the existing one.
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konrado5

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Re: My cables
« Reply #22 on: September 12, 2014, 06:51:46 PM »

Thank you burakkucat. It is good idea. It seems the external black cable is not as nearly the mains wiring as the internal CW1308 cable. Admittedly, the external black cable is as high as mains wiring however it is at the other side, deeper in the wall.

What type of cable should be used to connect phone socket with modem? I have CW1308 with RJ11 ends but some people say this cable shouldn't be used with RJ11 ends.

Best regards
konrado5
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kitz

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Re: My cables
« Reply #23 on: September 12, 2014, 08:19:20 PM »

Quote
What type of cable should be used to connect phone socket with modem? I have CW1308 with RJ11 ends but some people say this cable shouldn't be used with RJ11 ends.

You can use CW1308 with your RJ11's.   
CW1308 is better quality than CW1311/Flat cable or non-twisted which normally used with RJ11, if its crimped properly then its fine.  You could even use CAT5E..  as long as the cable quality is better then it shouldnt matter. 
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konrado5

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Re: My cables
« Reply #24 on: September 12, 2014, 08:31:28 PM »

Quote from: kitz
You could even use CAT5E.
I've heard CAT5e could give impedance mismatch if other cables are not CAT5E.

Best regards
konrado5
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HPsauce

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Re: My cables
« Reply #25 on: September 12, 2014, 08:51:17 PM »

Conversely, I use CW1308 with RJ11 ends as LAN cable around my house.
Works fine for 100mbps (if you use the appropriate 4 pins) and is less visible. That speed is fine as it's for internet connections.
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konrado5

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Re: My cables
« Reply #26 on: September 14, 2014, 05:30:20 PM »

I'd like to swap the internal CW1308 cable pair: white-blue to white-orange. I see white-blue is nearer to the wall and nearer to the doorbell cables. How to do it? Will I need new joints?

Best regards
konrado5
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boost

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Re: My cables
« Reply #27 on: September 15, 2014, 06:11:31 PM »

Have you considered removing the power source from the doorbell and checking what your QLN looks like after a resynch?

If there was even the smallest positive change I would be binning it and removing the bell from the front door and replacing with a knocker.

Also, have you considered reterminating your external cable, temporarily perhaps, by using a short run of any cable you like directly to an RJ11 jack into your modem? You could literally drape it down that wall as a test? Check HLOG on resynch?

My paint skills are dire but I've tried to visualise what I mean below:



In one fell swoop, you have built the case to palm this off to your ISP to investigate your dodgy pavement? Or... the new graphs present spectacularly smooth lines? :)
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konrado5

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Re: My cables
« Reply #28 on: September 15, 2014, 06:28:15 PM »

Quote from: boost
Have you considered removing the power source from the doorbell and checking what your QLN looks like after a resynch?
Unfortunately doorbell cable is not only mains cable nearly the phone cable. The round pink-painted box is mains box.
Quote from: boost
Also, have you considered reterminating your external cable, temporarily perhaps, by using a short run of any cable you like directly to an RJ11 jack into your modem? You could literally drape it down that wall as a test? Check HLOG on resynch?
Would I do it by cable with RJ11 on one leg?

Best regards
konrado5
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NewtronStar

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Re: My cables
« Reply #29 on: September 15, 2014, 09:11:32 PM »

There are flight tickets at the departure desk gate 6 Heathrow in the name of Walters Wheelbarrow destination Poznan International ETD 16/9/2014 2:00am  ETA 16/9/2014 3:45 am  :D
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