A real conundrum! Lend me your ears!

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StNick

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I think that this is a question for an electrician rather than a nerd, but with a bit of luck, someone out there is a bit of both and can help me with this extremely frustrating problem.

Some background points to be aware of:
1.) I have 10mb ADSL and have had it for a few years now.
2.) Although I have never had any issues with the line in that time, I know that I am at the limit with regard to how far one should be from the exchange. An SNR of at LEAST 5.5db is required for 10mbps ADSL, and I'm seeing anywhere between 6db and 8db when its working.
3.) About 8 months ago, I bought an inverter to combat load shedding and I have been extremely happy with it. It acts like a UPS and we don't even notice load shedding sometimes as the switch-over is seamless.

Right, now to the problem at hand! About two months ago, I noticed that my line was performing very badly. My SNR was down to 3.5db and my sync speed was anywhere between 8192 and 9000. Telkom came around and couldn't find any problems (to be honest, they didn't do anything that I hadn't already done myself). In the end, a port-reset fixed the line and he left. However, soon the problem was back again. Long-story short, I discovered that the issue was my inverter. When the inverter is plugged into mains, EVEN IF NOTHING IS PLUGGED INTO THE OUTPUT OF THE INVERTER, it is feeding back noise into the mains, and this is causing my SNR to drop on my ADSL line, thereby bringing it down. If I unplug the inverter from mains, everything bounces back to normal. Now, it isn't quite as simple as that unfortunately, since it isn't consistent. I can run the inverter for hours and the line is fine. I'm guessing that it is when the inverter is in a certain mode, it is inducing the noise (for example when it is trickle charging the batteries).

Plot twist: Last night I decided to hunt for any other issues I could find, and I discovered that if I turned off all my lights, things were better! The ADSL was fine, even with the inverter plugged in. I thought I'd nailed it! This morning, I awoke to find my ADSL poked, even with the lights off. AAARGH!

So my conclusion thus far is this:
1.) SOMETHING changed about two months ago. There is no way that I had this inverter running for 6 months and didn't notice my ADSL line dropping constantly.
2.) My ADSL line is BORDERLINE good enough for 10mb at the best of times.
3.) A combination of devices / appliances on my mains is causing enough noise to impact my ADSL line, the inverter being the biggest culprit.
4.) It is seemingly random, potentially based on the time of day - which leads me to suspect that perhaps one of my neighbours have recently bought a noisy device that is causing my issues.

If you have got this far without giving up, thanks. Almost there....

The questions I need answers to:
1.) Is there a device such as an in-line wall plug that I could plug the inverter into which would "clean" the feedback going back into my mains?
2.) Is there a device that I could put into my DB-board that would "clean" the entire input into my house in the event that my neighbours are to blame?
3.) Is there a device that I could use to test for noise on my mains? The ONLY way I know how to test this problem is by looking at my ADSL stats, and I would rather test it properly. Perhaps the noise is being induced on my phone line through the mains, but I can't test that.
4.) Any other suggestions?!

Thanks for listening... I'm at the end of my rope and would appreciate any and all input.
 
Think the first question would be : Is your inverter modified or pure sine wave?
 
How close is your inverter to your phone line?
 
Who is your ISP? I see the dreaded "something changed in the last two months" phrase.
 
Drifter said:
Who is your ISP? I see the dreaded "something changed in the last two months" phrase.
Click to expand...

No matter how much they'd like to, ISP's can't inject noise into an ADSL line ;)
 
Hey guys,

Thanks for the replies so far.

It is a 24V 1000W pure sine wave inverter. But just to clarify, even if there is absolutely nothing plugged into the output of the inverter, as long as it is on, and plugged into mains, the problem occurs (albeit randomly). If I yank the inverter from the mains, the problem goes away. Incidentally, even if the switch at the mains is OFF, the problem persists. I have to physically disconnect the inverter from the wall.

I use three ADSL ISPs, but that really is irrelevant. The issue is with the line sync. Even if I'm not dialled up at all, the problem is evident simply by looking at the ADSL stats on the modem.

The inverter is in my garage, far from my phone line; at least where it connects to my modem. I cannot say for certain that the phone line doesn't share conduit with mains at some point in the walls of the house though, so it is very possible that the noise is being induced into the phone line. I cannot test this though, as the only way I can see the problem occuring is on the ADSL modem stats. Hence the question about whether a device exists that can help me detect noise on the mains.
 
Last edited:
Check the following :
  1. Fluorescent lights near the router or plugged into the same socket (e.g. load shedding lights)
  2. Additional cordless phones added recently - unplug all of them from power and phone plug and check.
  3. Recent electric fence installations - yours or someone nearby. E.g. is the fence energizer near your inverter in the garage?
  4. Check any new appliances that were acquired around the time the issue started.
  5. Use a voltmeter and test the output from the router transformer - if it fluctuates etc.
  6. Try changing your modulation from ADSL2+ to ADSL and check if that improves the SNR but your sync speed may be lower if you do this.
  7. Also try connecting the inverter to a multiplug (the type with the reset button) instead of directly into the wall socket - check for crossed live/neutral if you added a plug to the inverter input.
 
Last edited:
If you are with Afrihost, then I can tell you, it's not your line or inverter :whistle:

I don't understand how the inverter could affect noise on the phone-line, unless the phone-line is running past the inverter or too close to poorly shielded electrical cables. I would perhaps check the phone-cable itself and see if you can not replace it completely.

What DSL modem are you using? Some models deal substantially better with SNR fluctuations than others. I found that switching from my Netgear DGND3700 to an ASUS DSLN66U improved line stability (the SNR seems to be better at it).
 
desiganp said:
Check the following :
  1. Fluorescent lights near the router or plugged into the same socket (e.g. load shedding lights)
  2. Additional cordless phones added recently - unplug all of them from power and phone plug and check.
  3. Recent electric fence installations - yours or someone nearby. E.g. is the fence energizer near your inverter in the garage?
  4. Check any new appliances that were acquired around the time the issue started.
  5. Use a voltmeter and test the output from the router transformer - if it fluctuates etc.
  6. Try changing your modulation from ADSL2+ to ADSL and check if that improves the SNR but your sync speed may be lower if you do this.
Click to expand...

We have no flourescent lights in the house at all. We DO have a cordless phone, but we've had it for years, and I've tried removing it already, to no avail. If I change to g.dmt modulation, the SNR problems are still there. Max line speed on g.dmt is 8mb anyway. I'll try the voltmeter thing. I wonder if a multimeter can tell me anything of worth by connecting it to the pos/neg of the plug going into the inverter?

I have two DSL modems (D-link and Billion), both produce the same results.
 
Is there such a thing as an ADSL filter (*not* a POTS filter) which might clean up any EMI on my phone line?
 
It does seem strange that you have to physically pull the plug out to stop the interference. Switching off should prevent any feedback into the socket unless something like the live and neutral are crossed (just a guess).

Have you tried changing the DSL filter on the line? Also try connecting the inverter via a multiplug (the type with the reset switch) as well as try connecting the inverter to another plug point which is on a separate breaker from the one in your garage. Most houses have about two breakers for plugs - 1 for the front and 1 for the back.
 
I think the next step should be physically inspecting the installation. Get up in the roof and have a look at the cables. If the phone line is in a conduit, jank that out and have a look.
 
Thanks for all the replies everyone.

I have tried the inverter on a different circuit / breaker but unfortunately the problem was still there. I have NOT tried putting it on a multiplug, so I will give that a go. I'd be surprised if that would work as those are merely for electrical surges right? This relates to the question I mentioned about whether you get such a thing as a EMI filter that I could first plug the inverter into (just like a multiplug).

As for the phone lines, I'm not sure I can get to the ones in the wall, but I'll have a look.

desiganp, when you say "Have you tried changing the DSL filter on the line?", do you mean the POTS filter that the phone is plugged into? There is no other filter on the line.
 
StNick said:
Is there such a thing as an ADSL filter (*not* a POTS filter) which might clean up any EMI on my phone line?
Click to expand...

If it is AC current causing EMI, the frequency should be quite low, 50 Hz and it's harmonics. So *technically* a high pass filter for ADSL should clean it up. Now I am not 100% sure, but most ADSL filters are just low pass filters for the analog signal.

The easiest way to be sure of interference is to use an oscilloscope to look at the frequency content of the line.
 
StNick said:
desiganp, when you say "Have you tried changing the DSL filter on the line?", do you mean the POTS filter that the phone is plugged into? There is no other filter on the line.
Click to expand...

  • Yeah the POTS filter. When you removed the cordless phone, did you remove the phone line from the base station as well?
  • Also try moving the router to the main telephone socket that comes in from the street (if it isn't already),
  • What happens when you power the router from the inverter output power instead of from the mains socket directly?
  • Any change when you have the inverter powered but remove the battery terminals?
  • Does your inverter having different modes e.g. standby, online etc. If so, try changing between these modes and check.
 
konfab said:
If it is AC current causing EMI, the frequency should be quite low, 50 Hz and it's harmonics. So *technically* a high pass filter for ADSL should clean it up. Now I am not 100% sure, but most ADSL filters are just low pass filters for the analog signal.

The easiest way to be sure of interference is to use an oscilloscope to look at the frequency content of the line.
Click to expand...

Answering my own question, it appears that modems are meant to contain their own high pass filters. Have you tried using a different modem. The filter part of your router/modem might be dysfunctional.
 
desiganp said:
  • Yeah the POTS filter. When you removed the cordless phone, did you remove the phone line from the base station as well?
  • Also try moving the router to the main telephone socket that comes in from the street (if it isn't already),
  • What happens when you power the router from the inverter output power instead of from the mains socket directly?
  • Any change when you have the inverter powered but remove the battery terminals?
  • Does your inverter having different modes e.g. standby, online etc. If so, try changing between these modes and check.
Click to expand...

* Have tried taking the cordless phone out of the equation altogether, no dice.
* This is a test I have not tried yet. Will do tonight!
* When everything is running off the inverter, the sync is solid. eg. During load shedding, the ADSL purrs.
* I haven't tried running the inverter when not connected to batteries. Worried it might damage it.
* There are no modes. Just on and off.

konfab, yes I have tried two modems, D-link and Billion.

One thing that could have changed in the last two months is that I moved the modem closer to my Mikrotik router. Some time ago, I rearranged my desk, and thinking back, the modem and router were spaced further apart. I wonder if the Mikrotik (it has a powerful wifi antenna) is interferring with the modem? Seems like a bit of a stretch though; we're talking about 30cm difference here....
 
Update: SUCCESS!

I purchased one of these for R150 or so from AC/DC and put it on the output of the inverter. Problem solved!

BsEpaNo.jpg

I don't understand why it works, but it does and that's all I care about. Thanks to everyone for the advice and suggestions! My rugby viewing this evening will uninterrupted when the lights go out at 18h00!
 
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