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Author Topic: My cables  (Read 19442 times)

JGO

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Re: My cables
« Reply #45 on: October 23, 2014, 04:44:05 PM »

My circuit is contradictory with laws of nature. :) It is normal that attenuation is lower when circuit is longer.

NO !   This is what Power Engineers think because they don't deal with long lengths of cable (long in wavelengths;  at 50 Hz the wavelength is c 6,000 km)  so they get away with ignoring the inductance and capacitance of the cable.   Doing this at radio frequencies, including xDSL, gives wrong answers. Your results on attenuation seem plausible if you don't have one single cable of the same type all the way.
 I suggest you read a book on Transmission Lines for the full theory.
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c6em

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Re: My cables
« Reply #46 on: October 23, 2014, 06:04:22 PM »

You'll be glad that this power engineer was taught extensive transmission line theory while at university.

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konrado5

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Re: My cables
« Reply #47 on: October 23, 2014, 07:18:01 PM »

I don't understand. Is it normal that some frequiences are more attenuated and some frequiences less attenuated if the line is longer? For example line is 1200 meters long. Attenuation at 900 kHz is 32 dB and attenuation at 1696 kHz is 40 dB. If line has 1230 meters, attenuation at 900 kHz is 30 dB and attenuation at 1696 kHz is 38 dB. Is it possible that 900 kHz signal travels 1200 meters and is 32 dB weaker than output signal and this signal is stronger (only 30 dB weaker) if it travels additional 30 meters? Furthermore, in the case of bridge tap, zeroing frequency (notch frequency) is depended on the lenght of bridge tap and not distance of socket to the bridge tap. I suspect that similar case is in the case of reflections caused by wire gauge changes. It should be not easy to change the reflected frequiences.

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konrado5
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konrado5

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Re: My cables
« Reply #48 on: October 26, 2014, 08:58:45 PM »

I took photo of my new socket.


Is second unused RJ11 contact bridge tap? Blue conductor is connected do two green conductors. White conductor is connected to two red conductors.

Now I have no circular box as in the old installation. I have external black cable connected directly to the rectangular phone socket with RJ11 connector. It implicates that at this moment external black cable is not connected by gel-crimps. Is it right?


Best regards
konrado5
« Last Edit: November 07, 2014, 01:10:33 AM by konrado5 »
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konrado5

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Re: My cables
« Reply #49 on: November 01, 2014, 02:54:49 PM »

I changed my two connectors phone socket on one connector phone socket. I don't see difference.

Best regards
konrado5
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burakkucat

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Re: My cables
« Reply #50 on: November 01, 2014, 11:05:58 PM »

I changed my two connectors phone socket on one connector phone socket. I don't see difference.

From that result you should therefore be confident that the circuit is as good as it can be. (I would have been very surprised if you had noticed any significant difference.)

JGO's comment about transmission line theory (for radio frequencies up to ~ 2MHz) and considering the capacitance, inductance, etc, as well as the DC resistance of your circuit, may help to explain some of the observations that you have made.
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konrado5

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Re: My cables
« Reply #51 on: November 01, 2014, 11:44:33 PM »

Thank you very much for your reply. How to diminish CRC errors when doorbell rings, lights are turned off, electric saw is used ? It seems that impulse noise from mains gets to the modem by modem power adapter.
Quote from: burakkucat
JGO's comment about transmission line theory (for radio frequencies up to ~ 2MHz) and considering the capacitance, inductance, etc, as well as the DC resistance of your circuit, may help to explain some of the observations that you have made.
Unfortunately I am ignorant of physics. Could you explain it clearly? Is it normal that shortening the circuit causes that some frequiences are less attenuated but other frequiences are more attenuated? It seems to me that on every frequence attenuation should be lower than before shortening unless something was damaged.

Is it normal that QLN on my starting downstream tones is higher after shortening circuit?

Best regards
konrado5
« Last Edit: November 01, 2014, 11:48:43 PM by konrado5 »
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NewtronStar

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Re: My cables
« Reply #52 on: November 02, 2014, 10:53:58 PM »

Thank you very much for your reply. How to diminish CRC errors when doorbell rings, lights are turned off, electric saw is used ? It seems that impulse noise from mains gets to the modem by modem power adapter.

I have done quite a lot of stuff around the house to lessen the effects of REIN but it's still get's through is it the internal broadband cable is it my mains wiring picking up REIN or the drop wire  :-\

You can only do so much to limit the effects of REIN and hang up your tools and feel proud with yourself for trying your best  ;)
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konrado5

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Re: My cables
« Reply #53 on: November 03, 2014, 04:05:50 PM »

Fortunately I have very little impulse noise (very short), only when my lights are turned off, doorbell rings. I'm curious what number of CRC errors I have if I would have no CRC errors from mains. Perhaps power strip with some kind of filter would be helpful.

Best regards
konrado5
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burakkucat

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Re: My cables
« Reply #54 on: November 03, 2014, 05:49:47 PM »

There is an experiment that you could perform to see if interference is induced into and carried by the mains power supply to your modem/router . . . That is to borrow a 12V car battery or power tool battery pack and run the modem/router from the battery for a period of time.
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konrado5

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Re: My cables
« Reply #55 on: November 03, 2014, 06:11:11 PM »

1. Thank you for suggestion. I've seen thread about car battery in this forum. They write that car battery causes other type of interferences:
http://forum.kitz.co.uk/index.php?topic=7448.0

2. What do you think about issue in reply #51 ?

Best regards
konrado5
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burakkucat

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Re: My cables
« Reply #56 on: November 03, 2014, 06:30:19 PM »

Sorry but I shall have to be brief --

1. A slightly discharged car battery (for example) will be close enough to 12V (if that is what your modem/router requires, of course). As I also mentioned, the battery pack from a power tool could be used. (I'm not sure who (without checking) but other kitizens have successfully experimented that way.)

2. Transmission line theory is something I know very little about. At best one needs to consider the (transmission) source, the terminating load (of the receiver), the resistance, the impedance, the capacitance and the inductance of all segments that make up the circuit. Undoubtedly complex numbers, differential equations and integrals will also be part of the theoretical mix. I tend to ignore the subject in detail and just regard it as a black-box effect. It is only when someone (like JGO) makes a mention of the subject do I realise that my simple DC circuit theory may not be giving the full picture. The (English) wikipedia page would be a good starting point for any understanding.
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konrado5

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Re: My cables
« Reply #57 on: November 03, 2014, 07:39:36 PM »

Is it surprise for you that I have slightly other Hlog after shortening the circuit. Hlog before shortening is hlogdiagmode5.png. Hlog after shortening is hlogdiagmode6.png. Do you see that some frequiences are more attenuated than before (around tone 200 and end of the graph)? Is it surprise for you that on my new QLN there is more noise at the start of downstream?
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konrado5

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Re: My cables
« Reply #58 on: November 03, 2014, 07:40:18 PM »

QLN
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NewtronStar

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Re: My cables
« Reply #59 on: November 03, 2014, 10:26:53 PM »

Sorry but I shall have to be brief --

1. A slightly discharged car battery (for example) will be close enough to 12V (if that is what your modem/router requires, of course). As I also mentioned, the battery pack from a power tool could be used. (I'm not sure who (without checking) but other kitizens have successfully experimented that way.)

Its something I would be interested in doing, this is something I did in my early teens running a CB radio from a car battery and if it needed charged hook up the car battery charger and you can always use a multimeter to check the volts before the experiment  ;)
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