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Author Topic: ADSL filters with FTTC  (Read 25674 times)

dfects

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Re: ADSL filters with FTTC
« Reply #60 on: September 26, 2016, 09:17:27 PM »

Will order the MK 3 SSFP, should be super easy to fit as there are no extensions :)

Assuming if the OR engineer had left the xnte connected I'd of had a whole host of issues with two nte's on the line? Shame I couldn't open the xnte to check.
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burakkucat

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Re: ADSL filters with FTTC
« Reply #61 on: September 26, 2016, 09:44:38 PM »

Well, in that case there would have been two resistive-capacitive shunts across the pair. I guess that remote testing would deduce that the line length is either longer or of a different make-up then reality.  :-\
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dfects

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Re: ADSL filters with FTTC
« Reply #62 on: September 26, 2016, 11:06:33 PM »

Hmm interesting :) I noticed some of the businesses connected to our cab were able to order fibre a few weeks before we were while we (the entire estate of 27 houses based on the few I checked) just got the following message:

"Your cabinet is enabled for Superfast fibre however you're not able to order fibre just yet. This might be because the length of the line is too long to get Superfast speeds. We're actively looking at other options. If you'd like us to let you know if fibre becomes available, register your details."

Pretty sure that's just a coincidence though as https://www.telecom-tariffs.co.uk/codelook.htm and Black Sheep (who was super kind enough to check a LOT for me) stated it wasn't showing as active, where it was shortly after I was able to order. Not sure if its usual for business premises to get fttc first  :-\
« Last Edit: September 26, 2016, 11:08:59 PM by dfects »
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NewtronStar

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Re: ADSL filters with FTTC
« Reply #63 on: September 27, 2016, 12:01:22 AM »

Now don't expect a massive change in stats dfects when the SSFP MK3 is installed it's very subtle in how it works but over a few weeks there should be less errored second & CRC events in the router logs  :fingers:
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dfects

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Re: ADSL filters with FTTC
« Reply #64 on: September 27, 2016, 10:25:38 AM »

I don't expect miracles :) If it improves connection speed/stability that's more of a bonus. Be nice to not have to wonder if the microfilter i'm using is hampering anything.

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dfects

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Re: ADSL filters with FTTC
« Reply #65 on: September 27, 2016, 05:35:50 PM »

I just had another go at opening the xnte to check it was bypassed, man that screw will not turn :lol: 3 different phillips #2 screwdrivers and it will not budge with literally all my strength to the point my arms were shaking. Thinking the guys superglued it in or something! I did notice the other end of the screw tunnel is open, not sure if there is a captive nut in there that's rusted tight or something. ???

Think the only way I'll ever see inside is by removing the rubber bung on the side and peering in with a torch  :P
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les-70

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Re: ADSL filters with FTTC
« Reply #66 on: September 27, 2016, 06:07:21 PM »

@burakkucat Don't you always have a double ring capacitor and resistor in place with a filtered faceplate. Both the back of the nte5 and the filter plate have one. I have aways hoped that 470k was big enough to ignore?
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burakkucat

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Re: ADSL filters with FTTC
« Reply #67 on: September 27, 2016, 07:44:22 PM »

As much as I would like to categorically say either "yes" or "no" I am restricted by not having access to the circuit diagrams of the SSFPs -- the original, the Mk 2, the Mk 3 and the Mk 4. (I have a suspicion that the Mk 3 & the Mk 4 are electronically identical and are just different physical presentations thereof.)

The more I think about the SSFPs, the more uncertain I become. I expect that an analysis of the components used will show a low-pass filter between the "network side" and the telephony port. I would not be surprised to know that there is also a high-pass filter between the "network side" and the xDSL port. I would be very surprised to know that there is yet another resistive-capacitive shunt across the "network side" as that is a necessary definition of the network termination. (I forget which SIN defines that requirement.) I would not be surprised to know that the "bell wire", originating within the NTE5, is provided with a further degree of decoupling before it transits to the lower front face-plate where it passes through a 22 mH choke before appearing on "pin 3" of the telephony port.

Hmm . . . Somewhere in the grotto I have both a broken Mk 2 and a broken Mk 3 SSFP. Given a bright light, a steady hand and good eyesight I guess it should be possible to sketch out the circuit. Application of ~50V DC across the "network side" and usage of a DMM should aid the identification of unknown circuit components. (The other alternative is to gain access to Grimbledon Down -- or whatever is the current name for Martlesham Heath / Adastral Park -- and look in the Wizards' archive of circuit diagrams.)

  :-\   :hmm:
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les-70

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Re: ADSL filters with FTTC
« Reply #68 on: September 27, 2016, 08:19:55 PM »

   You helpfully uploaded some photos a while ago http://forum.kitz.co.uk/index.php/topic,14381.msg269386.html#msg269386.  You need the board in your hand to see the circuit but the capacitor is clear and my recollection is that having junked the NTE5 bell wire by only  re connecting up the a and b the bell wire is regenerated directly between the incoming a and b.  My recollection is just that, as I was not really checking for that.

p.s.  As an aside and re http://forum.kitz.co.uk/index.php/topic,14381.msg269651.html#msg269651 I think the Mk3 choke is bifilar albeit not very well wound.  The one in my Mark 3 is tidier than the picture but it looks as though the second layer of bifilar winding spreads out unevenly over the first layer.
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burakkucat

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Re: ADSL filters with FTTC
« Reply #69 on: September 27, 2016, 08:49:32 PM »

The choke, to which you refer, is not for the "bell wire" but is for common-mode signal rejection. Of the two windings on that toroid, one is in series with the A-wire and the other is in series with the B-wire. Now that you have reminded me, I do recall looking at that choke on both the Mk 2 and the Mk 3 SSFPs.

With your assistance I do also recall that the plug of the SSFP only carries two connections, that are made via the "test" socket of the NTE5. Consequently the signal for the "bell wire" has to be regenerated on the SSFP. Hopefully that capacitor is connected to the downstream side of the low-pass filter and not the upstream side . . .  :-\

We really need --
  • to see the circuit diagram of the Mk 2 SSFP.
  • to see the circuit diagram of the Mk 3 SSFP.
  • an experimenter to remove the (above discussed) capacitor from the Mk 2 SSFP and check the resulting performance of the SSFP.
  • an experimenter to remove the (above discussed) capacitor from the Mk 3 SSFP and check the resulting performance of the SSFP.
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les-70

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Re: ADSL filters with FTTC
« Reply #70 on: September 28, 2016, 09:38:01 AM »

Here are pictures of both sides of a mark3.   I have yet to puzzle the circuit fully out regarding the regenerated bell wire.  It does look like your correct about the bell wire being regenerated after the filter but at first sight one end of the capacitor does not seem connected to anything!  :'(

[attachment deleted by admin]
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burakkucat

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Re: ADSL filters with FTTC
« Reply #71 on: September 28, 2016, 05:02:09 PM »

After my last post, yesterday evening, I went routing through the what-not (within the grotto) and extracted both the Mk 2 and the Mk 3 PCBs.

A quick look (with the aid of a magnifying glass) enables me to say that there is not a (duplicate) resistive-capacitive shunt across the pair. The "big yellow capacitor" just connects "terminal 3" to "terminal 2" (using the understood numbering as of the IDCs at an extension socket).

Interestingly I saw that the capacitor was marked "1u8K250V". I can translate the "1u8" to 1.8 micro-Farad and the "250V" to be the maximum voltage rating but the mention of Kelvin (the upper case "K" leaves me mystified. (Unless the "K" indicates the capacitor type . . . it's not electrolytic, so polyester would be my guess.)  :-\
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les-70

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Re: ADSL filters with FTTC
« Reply #72 on: September 28, 2016, 05:43:49 PM »

   I am puzzled over what is  providing the bell wire voltage unless that comes back from the phone.  It definitely does not come from the NTE5 and I agree that the  capacitor " just connects "terminal 3" to a filtered "terminal 2" ".     I assumed that something ought to be raising terminal 3 to terminal 5 voltage via a high resistance.  I have one wired phone that definitely needs a bell wire and it certainly rings with the MK3.  Does that imply that just the capacitor (which is the right value for the ring), connected between 2-3 is enough for the ring and the phone has the needed charging resistor?.  As I said I am puzzled.
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dfects

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Re: ADSL filters with FTTC
« Reply #73 on: September 28, 2016, 06:14:52 PM »

Internet resyced for the first time in about a week today, upload speed has increased to exactly 10 megabit (from 9.6), download speed still 32.40 exactly. Upload noise margin increased a little as did the downstream. Attenuation is .1 less   :P

DSL uptime:
0 Days, 8 Hours 55 Minutes 44 Seconds
Data rate:
10.00 mbps / 32.40 mbps
Maximum data rate:
10000 / 38508
Noise margin:
6.7 / 8.9
Line attenuation:
25

We're about 1km in cable length from the cabinet (thanks to black sheep for looking this up), upload speed is over performing the estimate by nearly 3mb, download is at the lower end of the estimate  :-\
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Dray

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Re: ADSL filters with FTTC
« Reply #74 on: September 28, 2016, 06:20:42 PM »

The MKT 82 is a Metallized-Polyester-Film Capacitor

I believe the k refers to a tolerance of 10%
« Last Edit: September 28, 2016, 06:31:52 PM by Dray »
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