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Author Topic: Daily DS SNRM Drops  (Read 7217 times)

g3uiss

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Re: Daily DS SNRM Drops
« Reply #45 on: October 04, 2019, 12:11:33 PM »

I've been looking around for an example of the circuit diagram for a mains EMI filter. Attached, below, is typical example. (It's not a recommendation for that actual Chinese made device!)

If that circuit diagram needs to be "translated" into English sentences, please just ask. I'm sure quite a few of us will be capable of doing so . . .

Great, no difficulty with circuit diagram being well used to those. Just thinking of a neat way to house and terminate in an AC plug and socket.
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Zen FTTC and Plusnet ADSL HG612 modems with Vigor 2925

burakkucat

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Re: Daily DS SNRM Drops
« Reply #46 on: October 04, 2019, 04:17:26 PM »

Very close format and practically identical component wise to this unit e-Bay Bare Mains Filter I listed earlier in the thread, also made in China, majority of things are these days.

In this particular case, I would not consider purchasing a used item.
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burakkucat

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Re: Daily DS SNRM Drops
« Reply #47 on: October 04, 2019, 04:23:16 PM »

The ultimate test, as the approximate time of the interference is known, would be to temporarily power the modem/router from a sealed lead-acid battery of sufficient capacity. If the problem is still seen, then it cannot be due to transmission via the mains supply.
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g3uiss

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Re: Daily DS SNRM Drops
« Reply #48 on: October 17, 2019, 10:48:27 PM »

As all my kit is UPS protected, I removed the AC to the UPS. It ran on battery over the time period and the errors remained unchanged.
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burakkucat

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Re: Daily DS SNRM Drops
« Reply #49 on: October 17, 2019, 11:09:23 PM »

So mains-borne transmission can now be ruled out.
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Octal

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Re: Daily DS SNRM Drops
« Reply #50 on: November 17, 2019, 11:51:00 AM »

I know I'm a bit late on parade as it's now November. I'm just wondering how you are getting on with you line problems?

One way I cured mine was to fit a common mode choke on the incoming line like this:



Previously to fitting this when I used my transmitter on 1.9mHz it used to kill my modem stone dead, after fitting it I just lose some of the tones around that frequency, a modem re-boot brings them back when I've finished, it has generally cleaned up my line no end and just get a few CRC errors during the day. The torriod I used was 43 mix, I think 31 mix would be better as that is intended to cover lower frequencies that ADSL2+ uses.

You can get the torriods from here:
https://radio-store.co.uk/toroids-rings/12-fair-rite-ft240-31.html

You mileage might vary of course, like any EMC problems it is a case of experimenting to see what works. Incidentally, it will help with line balance as well.
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g3uiss

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Re: Daily DS SNRM Drops
« Reply #51 on: November 18, 2019, 06:01:07 PM »

Interesting Iíve tried a ferrite bead but not a choke. I will give your suggestion a try

Thanks
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g3uiss

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Re: Daily DS SNRM Drops
« Reply #52 on: May 18, 2020, 05:30:05 PM »

Having tried all the helpful recommendations nothing has solved the problem. I know @kitz has a similar problem, but mine is EXACTLY the same time daily. A daily resync on ADSL2 is not in its self a major problem, and if I didnít know I likely might not know.

However similar to @kitz occasionally the resync happens during the burst giving a high SNRM and ES needing a manual resync to sort. Also it drops my VPN, again this re syncs but potential at a low speed.

Given OR wouldnít be able to find this, are there any mitigationís I could try to try and hang on to sync. Perhaps getting the SNRM altered to 9db so a drop might not go to minus and hold sync ? Or having the line interleaved? I would "Cap" the speed, but I don't think you can do that with ADSL2 on a HG612 ?

My VDSL circuit suffers the same but a small dip in SNRM for the same CRC burst, and ES burst, and always stays in sync. Iím assuming the interference is either at the lower tones, or nearer the exchange than the cab. Hence the reduced effect on my VDSL.

Suggestions welcome.

Tony
« Last Edit: May 18, 2020, 06:15:26 PM by g3uiss »
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