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Author Topic: SSFP Mk 3  (Read 70326 times)

les-70

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Re: SSFP Mk 3
« Reply #135 on: October 23, 2014, 07:20:26 PM »

  I decided to have go at doing a better job of adding a common mode choke to the Mark 1 perhaps to make a Mark 4  :).  From reading references earlier in this thread it is disappointing that the Mark 3 choke is not bifilar as a bifilar choke should be able to do a much better job on the common mode with much less differential mode impact.

   I have taken a ferrite toroid with Al value 12 micro Henry and wound my adsl lead round it.  I have tried 10 turns, 7 turms and 5 turns and settled on 5 turns for a ~70Mb/s connection.  For a  lower sync speed more turns should be better.  5 turns gives me a sync speed loss of about 1Mb/s (similar to a Mark 2) more turns give a bigger reduction.   I attach Hlog with and without the toroid and a phote of the toroid itself.  In Hlog you can see the differential mode attenuation starting to bite.  That should have the effect of stopping any higher frequencies saturating the modem input stage.   The common mode attenuation can be calculated from the Al value and number of turns and should be enough to give good common mode rejection over the vdsl band.

 Unlike the Mark2 and mark 3 this arrangement does have a helpful impact on my errors.   :)  I have been using it for 3 days and the whilst the ES are down a bit the CRC and SES are down much more.   I will need a week more to give a confident outcome but I like being able to control the filter with the number of turns
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NewtronStar

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Re: SSFP Mk 3
« Reply #136 on: October 23, 2014, 07:54:13 PM »

I replaced my old worn bathroom pull switch guess what no more crc's or errored seconds when someone pulls that cord, tbh have given up all hope on MK's it much easyier to find the cause in the household and fix it than getting an MK Device that supposedly subdues the effects of rein.
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burakkucat

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Re: SSFP Mk 3
« Reply #137 on: October 23, 2014, 09:08:20 PM »

phote of the toroid itself.

Looking at the picture, I make that six turns of the cable on the toroid.  :-\
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burakkucat

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Re: SSFP Mk 3
« Reply #138 on: October 23, 2014, 09:09:31 PM »

I replaced my old worn bathroom pull switch guess what no more crc's or errored seconds when someone pulls that cord,

A definite result! :clap2:
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les-70

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Re: SSFP Mk 3
« Reply #139 on: October 23, 2014, 09:32:26 PM »

  It is indeed 6, I clearly can't count!  :(  If you believe Wikipedia that makes the individual inductance's  in extra of the cables of the pair as 12*36 =432 micro H. with an impedance of 2.714 Kohms at 1Mhz and more than enough to kill any common mode.  I wonder how much of any benefit comes from the common mode rejection vs. just attenuating the higher than vdsl frequencies that might saturate an input stage.
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NewtronStar

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Re: SSFP Mk 3
« Reply #140 on: October 23, 2014, 09:33:41 PM »


A definite result! :clap2:

It is and the kitchen also has a pull switch which shows up as crc's and errored seconds when pulled so that's another 45 min replacement job, if it was not for Dslstats or HG612_Modem_stats I would never have been able to see the correlation how a switch can effect the modem  :)
« Last Edit: October 23, 2014, 09:39:58 PM by NewtronStar »
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boost

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Re: SSFP Mk 3
« Reply #141 on: October 23, 2014, 09:43:49 PM »

wp les!
Could I try this for good ole ADSL1? 702 turns maybe? :D
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NewtronStar

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Re: SSFP Mk 3
« Reply #142 on: October 24, 2014, 12:21:30 AM »

You can make your own mind up as I have removed the MK2 tonight it's been inplace for over two weeks and replaced it with the standard SSFP, to me the SSFP MK1 is less sensitive to LCD and LED monitors.

when the MK2 was inplace it impacted my SNRM big time when LCD and LED TV's & Monitors were on can't figure that out.

With the standard SSFP inplace there is less US CRC & Errored seconds when the phone rings again can't figure that out, now I haven't tried out the MK3 because I hate wasting money  ;)
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les-70

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Re: SSFP Mk 3
« Reply #143 on: October 24, 2014, 07:45:33 AM »

wp les!
Could I try this for good ole ADSL1? 702 turns maybe? :D

  The point is that with bifilar winding the common mode rejection is much much greater relative to the mostly unwanted differential mode attenuation and even with 6 turns that toroid may/probably outperform an RF3 in common mode rejection.  Even if you wanted to optimize the differential mode attenuation for adsl, it is not quite that many turns!  Inductance is proportional to turns squared.  Ideally you might need about 24 turns but as many as you could fit on that toroid, about 11 with the lead shown, should very greatly outperform an RF3.  Unless it is needed it still won't make any difference to the connection though!! (Most of the rubbish we would all like to reject is differenial mode at the actually signal frequency and that can't be just filtered out.) Those extra turns are not needed to reject any common mode but just to attenuate differential mode at higher than adsl2 frequencies, the result would be a vdsl killer. See pages 7 and 8 in link.

  http://www.we-online.com/web/fr/index.php/show/media/07_electronic_components/toolbox_1/product_training/Product_Training_CMC_100728.pdf
« Last Edit: October 24, 2014, 07:49:37 AM by les-70 »
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boost

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Re: SSFP Mk 3
« Reply #144 on: October 25, 2014, 02:10:48 PM »

Cheers, I will have a squint :)
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Ixel

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Re: SSFP Mk 3
« Reply #145 on: October 26, 2014, 10:29:38 AM »

I have taken a ferrite toroid with Al value 12 micro Henry

Is it possible to buy one of these (most probably a pack) online? I'm not an electronics expert so no clue what I'm looking for other than a ferrite toroid which has a diameter large enough for the RJ11 plug to fit through so I can wind it round the ferrite toroid. I presume ferrite toroids have varying thicknesses and dimensions, and 'Al value 12 micro Henry?'. I'm interested in trying this, I've been trying various methods to eliminate/minimise CRC errors on my downstream but nothing as customised as this. Any help is appreciated. Thanks.
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les-70

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Re: SSFP Mk 3
« Reply #146 on: October 26, 2014, 11:02:01 AM »

   Having had a longer test run,  an error reduction has remained but only about 20-30%.  I have now gone back to 11 turns to see if that does any better (which is most I can manage with my twisted pair cable).  The extra loss in sync with 11 turns is much less that I would have expected, I guess the  capacitive coupling part these devices is very hard for any non expert such as me to judge.   13 or 14 turns are possible with the usual modem supplied RJ11 leads.  The worst issue with all filters is that you just can't eliminate any unwanted differential signal in the adsl or vdsl tone band without taking the needed signal away at the same time. 

   It is also worth noting that I have a noisy line and probably more to try to get rid of.

  I would not expect too much.  The one I have is from

 http://www.ebay.co.uk/itm/290913639269?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

  It came in about a week.

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Ixel

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Re: SSFP Mk 3
« Reply #147 on: October 26, 2014, 11:21:43 AM »

Thanks. I've now ordered one and a MK3 SSFP. I'll post a conclusion when I've tested for a bit.
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JGO

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Re: SSFP Mk 3
« Reply #148 on: October 26, 2014, 12:34:00 PM »

In my case I suspect that many CRCs are due to nearby thunderstorms. In that case there is so much interference power there that NO practicable filter could reduce it below the systems's acceptable noise, even if the filter does an adequate job on say, street lights.
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burakkucat

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Re: SSFP Mk 3
« Reply #149 on: October 26, 2014, 03:07:08 PM »

. . . (which is most I can manage with my twisted pair cable).

I'm unsure Les but when using an UTP cable can it then actually be regarded as a bifilar winding? The tingle I currently feel in my whiskers seems to be hinting at "No".  :-\
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