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[sevenlayermuddle]

@Jack,

Do you know whether the inverter you are using produces a pure sine wave or (as most do), a so called 'modified sine wave'?

It's the 'modified sine wave' devices I'd be most concerned about, as 'modified sine wave' is really just marketing-talk for something that's simply not a sine wave. Often, or so I've read, these 'modified sine wave' devices would be better described as 'modified square wave', but that wouldn't sound so good.   Anything other than a pure sine wave contains components from higher frequencies.  A true square wave, for example, is the sum of an infinite series of  components of higher frequency and diminishing strengths, which is why square waves are so good at penetrating past anything in their paths.   It's these high frequency components that I'd anticipate could spell trouble for DSL devices, from induction-coupling to the phone lines and router leads.

- 7LM

[jack21]

@7LM

The inverter is a Belkin DC Anywhere 140W and is described as having a modified sine wave output. It ran for 10 hours purely on battery yesterday (no charger connected) and although slightly audibly noisy (no worse than many PC PSUs), did what it promised. It drew 1a exactly from the battery (which lasted for 10 hours before causing the inverter to give a low voltage alarm). I can't say I detected any interference from it being on-off-on, via RS graphs, whereas a rogue PSU I have gave an immediate 3db drop on RS  when powered up and connected to an unplugged-from-mains PC via USB......but not until it uses the PC as a generator/propogator.

[jack21]

Final Update:

On battery/inverter from 18:00, resulting in no discernable difference to it being on mains prior to then.
Every 45 minutes I then alternated between battery/inverter and mains, not noticing any real difference in SNRM trend between the 2 methods, other than a very slight smoothing of fluctuation when on battery, and a very slight increase in spiking when on mains. Even when the evening SNRM deterioration began, there wasn't much in it, and I eventually returned permanently to mains at 23:00.

Thats the end of the battery/inverter/router experiment; the setup certainly wasn't worse than the normal mains usage, but any improvement was very slight overall, and I won't be further employing the technique. At least it has put to rest, in my mind, the question of whether any significant interference reaches the router directly thru the mains. Phoneline plus radiation seem the most significant

BTW: Running the battery/inverter to power a separate, non-DSL-connected router whilst the principal router was running on mains, produced no detectable effect on the online RouterStats SNRM graph.

The wild behaviour of the SNRM at 22:00 onwards last evening was absent this evening. Maybe because its very rainy today/tonight, my new neighbour hasn't switched on his two powerful garden lights (aids to moth attracting/studying) - a clue to be followed up at some stage.

[roseway]

I think that, even if the experiment didn't deliver a significant improvement, it's still added something to our knowledge of the subject, and it's been very worthwhile from that point of view. Thanks for the detailed reports.

[jack21]

Thanks for that, Eric; I enjoyed experimenting!

Battery+inverter+PSU v Battery Alone

Some earlier comments raised concern that the inverter might cause much interference. The experiments I'd run didn't show that, but just to settle my own mind, this morning I did a back-to-back test, firstly with mains, then battery+inverter, then mains again, then battery only (direct to router). The results showed no significant difference between all 3 modes, except for the very slight smoothing of the SNRM variation when the mains are absent, so I conclude that the inverter isn't causing any ill-effects.

Before using battery-direct to router, I checked out the method using a Billion 7202, which I was prepared to risk! There was no problem, so I switched back to my DG834 V4 for the tests above. I'd prepared the battery such that it began its battery-direct test with 12.2v, and by the end of its test, the voltage had reduced to 11.97.

[jack21]

PS  The battery-direct method is considerably less demanding than the battery/inverter/PSU path; battery-direct consumes 0.5A, whereas the inverter method consumes 1.0A........so the battery ought to last twice as long!

[sevenlayermuddle]

Yes, interesting, thanks for doing these experiments.

I guess the evidence is that the inverter isn't producing much interference via induction, at least in your environment.   I'd say it's still possible that it's 240V output line may or may not be 'noisy' but, if it is, then the power-brick is probably preventing  that noise from reaching the router which is still fine.

RE battery power:
I wasn't prepared to encourage you to do any battery-direct tests in case your router chose that moment to die, but it's also worth bearing in mind that the Netgear power bricks, or mine at least, are not well regulated.  I just checked the brick from a DG834GT, and the open circuit voltage is about 15.5 Volts.   I can't  measure 'normal load' voltage as the router died some months ago, but I'd assume it will be closer to 12V.

I can't help thinking that if the router were easily susceptible to damage from over-voltage, then NG would have given it a more closely regulated PSU.    Then again, I can't blame you for being cautious, and I'd probably not have volunteered to put it to the test myself either with full battery voltage  

- 7LM

[jack21]

Having read Waltergmw's comments about the 2700HGV having an in-built Faraday Cage, I did a little reading-up, constructed one out of 2 heavy duty aluminium trays, sandwiched together and sealed by adhesive aluminium tape. Prior to sealing, I placed a wired-up DG834GT with DSL, Ethernet and power cable inside, leading the cables thru a small slot which I then sealed with further aluminium tape. I connected an earth wire to the assembly...no ventilation holes!.....connected all cables and powered up (router on battery-direct).

Results: No discernable difference to the prior RS graph and bitloading data; SNRM spikes still present.

I activated my rogue PSU, and the same 3db drop happened as would previously happen.

Assuming the cage is correct, does that now rule out every other source of DSL contamination other than what's delivered via the DSL cable?

[waltergmw]

Top marks for being so resourceful !

Dealing with radio frequency propagation is I believe very much a black art.
Perhaps 7LM and others could comment more upon this subject.
However I suggest it would be wise to disable the wireless function on the DG834GT if you haven't done so already.

Kind regards,
Walter

[sevenlayermuddle]

Assuming the cage is correct, does that now rule out every other source of DSL contamination other than what's delivered via the DSL cable?

Yes, I'd agree.  It certainly suggests to me that what little interference (if any) is entering the router by other means, is dwarfed by what's delivered via the DSL cable.  As for the rogue PSU, I'd speculate that its interference is carried into the mains wiring, which then acts as an effective transmitter antenna, the phone & DSL cables then acting as receiving antenna. 

I think I already mentioned I have some LV halogen downlighters in the kitchen, and have identified their transformers (which are actually switch-mode PSUs) as the cause of a 2dB step change in my own SNRM.  I've always assumed the interference path is as above, the transformers injecting noise into the mains, and then finding its way into the phone/router wiring.  In my case, I have the luxury of a piffling 56dB attenuation, so the interference from the lights is just a curiousity that I can live with, I still get decent speeds.  In your case it must be more of a problem, you're doing pretty darned well for a 68.5 dB line, and it must be frustrating whenever any interference arises and knocks it for six.

Incidentally, as of a few months ago, I also suffer from occasional spikes that kill the connection, up to three or four times a day.  There's no gradual decay in SNRM, just a sudden drop to less than zero SNRM, an immediate disconnect then, by the time the router reconnects again all is well, and it reconnects at good sync speed. It all seemed to start when my neighbours returned from a long holiday which is my only clue, but quite a big one.   I've a suspicion of maybe his bathroom extractor fan, or maybe a fridge thermostat,  but it's hard to prove anything.

So,  I strongly sympathise with your efforts to improve the issue - again, my problems are minor in comparison.   

[jack21]

@7LM

Thanks again, I've come to terms with my distance/line/attenuation, knowing there's nothing I can practically do about them. Even with the fact that 'my' telegraph pole seems to be worse than others in either direction in the village in delivering sync rates. In the village, we all get above the BT database spec of 512kbps, so I realise there's nothing I can complain of to them. Its the things that I just might be able to affect that niggle me, such as (prior to my experiments), identifying  the best modem/router and settings for the conditions - done - making the best wiring scenario in-house - done - minimising/eliminating any interference from within premises - done - eliminating conducted mains interference - done (there was none) - and trying to minimise interference from outside my immediate control, if I can. Practically, I can't really hope to identify interference from neighbour's property and expect them to allow me to dabble with their equipment.

But, as something of a hobby in my retirement,  I do offer a computer/broadband/software assistance service to friends/aquaintances/older citizens within our 2 villages, and sometimes the opportunity to fix a problem which affects more than just the 'owner' does crop up. Like the previous chap next door whose problematic power issues affected all his neighbours.

The fact that I'm down to the incoming phone line as the 'bringer' of interference, whatever its origin, is something I can accept as outside my sphere of influence, so the past days of experiments have been a confirmation that I've done all I can to improve my broadband lot.

The 1500kbps profile I aim for is fine for almost all my purposes - I can't say it is a problem - it is way up on the 90-120kbps I got as a newcomer to broadband 3 years ago, before I had the benefit of this forum  (and which I still occasionally find at 'clients' premises - eg one chap on 118kbps who is now on 3000). But I'm always trying to squeeze a bit more when I can, and I have got at least 1 more procedural approach to try out - and more may arise!

Cheers,
Jack

[HPsauce]

The more you improve your understanding the better your assistance to others will be.