Thanks!

The highlight was a bit naff wasn't it. Sorry

Shame that the signature doesnt change for posts made before the change

In reply to a post by greenglide:

You and Batboy friends?

It won't last!

Indeed we are - and (I think [cough]) it will last. It is perfectly possible to be friends with someone and disagree strongly with them occasionally.

Though he and I seem to disagree less and less often. Maybe one or both of us should be worried about that .

"Well over a million HomePlug devices in use in the UK so should have wiped out the amatuer radio, crashed a few planes and reduced ADSL to zero throughput by now "

[You call it Homeplug, I'll call it PLT, we mean the same thing]

Amateur radio clearly has been affected; there is plenty of evidence (although sometimes there is also more heat than light being shed on the subject).

ADSL throughput: where would what you call "evidence" come from, how much would it cost to get it, and who should be doing those investigations?

Whatever the area, the evidence is likely to come from long and tedious investigations. Other products sometimes interfere with DSL, but when properly designed properly certified products interfere with DSL it's generally down to faulty components which can be fixed. When these faulty products (Sky boxes, whatever) are identified as the source of a DSL problem it is typically after a long, tedious, expensive investigation requiring specialist skills (skills which just happen to be the same kind of skills some radio amateurs might have). Anyway once the problem is eventually identified the fix is usually easy - replace the offending item with a non-faulty one, and everyone is happy.

PLT kit doesn't just interfere when components go faulty. PLT kit interferes as a direct consequence of its intended design and use.

Anyone who's followed AG/TB for a significant time knows that getting unusual DSL faults fixed or investigated can be painfully tedious at the best of times. Who really thinks those expensive investigations are going to happen when a "quick fix" such as a pair swap will in many cases fix the symptom (in the short term) without too much effort or cost to the DSL supplier? Who cares if the pair swap doesn't really fix the underlying problem, just hides it till next time someone's DSL is affected?

Oh, and the field technicians who would be doing any UK investigation work for the same plc which is the biggest UK seller of the interfering product. That investigation's not gonna happen, is it, because it's inconvenient and expensive. So there's not going to be any "evidence" from that source is there. And there are DSL experts in the standards/R+D part of that same plc who know the full story too, but they too have bills and mortgages to pay, and they know exactly what would happen if they told their side of the story.

Yet there is plenty of proof that the interference from PLT can exist, and does exist, and that the interference is a necessary consequence of the basic product design especially in combination with UK wiring practices.

There is good reason based on the fundamentals of physics and RF propagation to believe that the interference will get worse everywhere that more PLT kit is deployed and as PLT speeds increase. Yes the interference may not occur in 100% of installations for 100% of the time, just as MW and SW reception varies by location and time. No surprise there.

Absence of evidence is not evidence of absence.

PLT is defective by design.

+1

In reply to a post by Anonymous:

"Well over a million HomePlug devices in use in the UK so should have wiped out the amatuer radio, crashed a few planes and reduced ADSL to zero throughput by now "

Absence of evidence is not evidence of absence.

So when can we expect a plane crash disaster due to HomePlugs?

Isn't amateur radio interfering with (non-Homeplug) DSL usage much more of an issue to the general public?

If a licenced radio amateur is found to be causing unwarranted interference with other uses of the radio spectrum, then there are procedures in place, procedures happily agreed by the amateurs, for addressing such interference. If the amateur's kit is misbehaving, it will be fixed (or removed from use). If the amateur is misbehaving, the licence can be revoked (or worse).

If the radio amateur's use is legitimate under the licence but is causing interference due to bad design of (or faults in) other equipment (e.g. consumer electronics which has insufficient rejection of out-of-band signals) then any decent amateur will generally work with the affected party to resolve things amicably, often involving a few pence worth of attenuators or RFI fiters on cabling. In the unlikely event that the particular amateur involved happens to be an awkward git (they exist everywhere), other more sensible amateurs will generally help out; it's in everyone's interests to do so.

Where's the problem with that?

You can't fix PLT kit with simple fixes like that. PLT kit is designed to send significant levels of wideband RF interference down mains cable. It is designed to receive RF from mains cable. If you stop PLT kit transmitting RF interference down mains cable, it no longer performs as advertised, and no one will buy it.

The fact that PLT vendors have had to agree to "notch" their unlicenced transmissions in order to keep out of the way of a small number of legitmate spectrum users is effectively an admission that their use of masses of the remaining "un notched" RF spectrum is neither authorised nor legitimate. And without unlicenced (ab)use of masses of RF spectrum, their products cannot work in any meaningful reliable way.

Ye canna change the laws of physics, cap'n.

Defective by design.

See also related recent discussion on
http://forums.theregister.co.uk/forum/1/2012/08/20/p...


Batboy: I'm not familiar with any recent aircraft-comms-related claims in this context. Are you?

I do have a vague recollection of a mention of that kind of thing in various of the Radio Authority's PLT Technical Working Group reports a decade or so ago, but I haven't re-read them lately and can't remember the details from back then. Do you remember them, or is there perhaps a current equivalent you're familiar with?

In reply to a post by Anonymous:

If a licenced radio amateur is found to be causing unwarranted interference with other uses of the radio spectrum, then there are procedures in place, procedures happily agreed by the amateurs, for addressing such interference. If the amateur's kit is misbehaving, it will be fixed (or removed from use). If the amateur is misbehaving, the licence can be revoked (or worse).

In reply to a post by Anonymous:

"... the evidence is likely to come from long and tedious investigations.

The person affected will be totally unaware of the effect of amateur radio, and probably equally unaware that his broadband is screwed by it. He just knows it isn't as good as what he reads about in the press or adverts.

The problem will not be reported, never mind "long and tedious investigations" requiring a specialist Openreach employee being requested, with a threat of a potential bill to the user of well over £100.

Your arguments make technical sense, but seem to come from an ivory tower.

Maybe if I do bin plots with router sat on top of a HomePlug when switch on and off we will see the clear a wiping out of swathes of the bins. If I recall I do see bins lost due to a couple of AM radio stations.

NOTE: Not saying I have never seen seen problems reported, remember a clear case of a wireless mouse not working when Comtrend units were used. The incidence level is around that of Plasma TV's causing issues, and tread mills.

"The person affected will be totally unaware of the effect of >>xyz<<, and probably equally unaware that his broadband is screwed by it. He just knows it isn't as good as what he reads about in the press or adverts.

The problem will not be reported, never mind "long and tedious investigations" requiring a specialist Openreach employee being requested, with a threat of a potential bill to the user of well over £100."

Exactly. I'm quite happy with that, whether xyz might be amateur radio, or might equally be PLT.

Licenced radio amateaurs have the use of a tiny tiny tiny part of the RF spectrum, therefore their effects (on DSL and other spectrum users) are necessarily limited. In reality there also aren't many of them around.

And well designed DSL kit together with well designed regulatorily approved amateur transmitters can happily coexist. If amateur transmissions do occasionally get in the way of a DSL connection, the DSL kit will hopefully just avoid the small number of bins which may be affected, leaving the rest to continue doing what they usually do. In the unlikely event that the amateur transmissions do have sufficient adverse effects that an investigation does occur, there are remedies that can be applied, and everybody can be happy.

The same does not apply to PLT.

For PLT to work as advertised it necessarily needs to use masses of RF spectrum. As PLT is more widely used and as it attempts to increase its speeds it will increasingly frequently interfere with the legitimate users of that RF spectrum. That's just basic physics, you can't avoid it.

As you rightly point out, it will be difficult for the man in the street (or even the SFI technician with the skills) to identify a particular PLT installation as the cause of any given misbehaviour.

But it has clearly been shown already that such misbehaviour can and will occur in the presence of unwanted RF signals. That's the reason that electronics kit has to meet certain regulatory approvals (the EMC regulations which the PLT people want changed so their kit can SHOUT LOUDER down the mains).

In the unlikely event that a PLT installation is identified as the cause of DSL problems there are probably no practical remedies (other than not using PLT).

Just say no, unless PLT can meet the same RF regulatory requirements as other electronics. And it can't. By design.