Homeplugs

In article , Bill Wright
wrote:
Steve Thackery wrote:


A few years ago I had experience of a similar thing. I fitted a
reversing monitor screen in the motorhome and found that it increased
the noise on the FM band. The noise as seen on the analyser didn't look
too terrible, and in a very strong reception area there was no effect,
but anywhere else reception was limited and would come and go as I drove
along. Reception of weak stations was impossible. I estimated that it
was having the same effect as if the transmitters had all been turned
down 15dB.

Traditional FM/VHF relies on having a decent CNR.[1] With a good CNR and
decent tuner you can get excellent results. But any wideband noise with a
pattern can be expected to demodulate and degrade performance.

DAB has a lower CNR requirement. But the TX powers are lower anyway to take
that into account. And there even a modest fall in CNR can have a dire
effect on reception.

For me the significant point here isn't just the worrying level of the RFI.
It is the extension up into the 100MHz region. Add in nonlinear
conversions by poor wiring or PSUs via direct injection coupling and this
could affect even more people.


Who was it said that PLT was unnecessary because you could do the same
job with a couple of quid's worth of CAT5e? It's not the cost of
CAT5e that matters, it's the faff involved in drilling walls,
cleating it, and having to look at the ugly stuff afterwards.
Speaking as a person who runs cables about domestic premises on a daily
basis, I don't think there's likely to be much 'faff' in getting a thin
cable like that from A to B. I can never understand why people are so
scared of running cables about. Once it's done it's done.

I'm also baffled by this. I'm hopeless at DIY but fitted ethernet around
the rooms in out house in a couple of hours. Seemed a trivial job to me.

If wired is felt to be terribly hard, there are dedicated local wireless
methods that comply with RFI requirements and don't squirt their signals
directly into the mains.

So far as I can see, for most people either of the above approaches should
be quite feasible. Also wired may well work far better.


Slainte,

Jim

[1] IIRC the 'process gain' of Band II FM is around 40dB. i.e. you need an
inband CNR or around 30dB or more to get a 70dB SNR for the audio output.
Note that is for *mono*. Stereo needs something around 10dB more IIRC.
Can't recall the exact values, but I think it is of that order. Any
reduction in CNR from that will have a direct impact on output, and any FM
demod of the hash within the output bandwidth will produce audio. So if the
data has a typical hopped or OFDM behaviour with slots that generate
something below the stereo MPX range it can give audio.

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In message , Jim Lesurf
writes



I must say I was myself quite shocked by the BBC findings. The problem does
seem likely to be worse than I'd assumed.

I recalled seeing that Maplin, in their product Q & A bit, did admit
that PLT could cause interference. A quick Google produced this:
http://www.ban-plt.co.uk/truth-lies.php
Some of the links are quite revealing. Only those with a "Who the hell
cares anyway" attitude could fail to be concerned about the state we are
now in, and how we got there. Just as important is the question of what
we're going to do about it.
--
Ian

In message on Thu, 14 Apr 2011 11:49:42 +0100
I'm Old Gregg wrote:



Try this

www.globalgadgetuk.com/Personal.htm


Greg

Wonderful!

"Note for UK customers: jamming equipment is illegal to use in the UK as it
violates section 8 of the 2006 Wireless Telegraphy Act, we are therefore
unable to supply jammers to any UK customer with the exception of certain
military and government departments who have the necessary authorisation from
the UK Office of Communications (Ofcom). Please note that no exceptions can be
made on this policy.

Due to non CE approval of these products we cannot sell these products into any
European Union country.

SH066PL2B £120.00 GBP"

And since when has the UK been outside the EU?

--

Terry

In message , Terry
Casey writes
In message on Thu, 14 Apr 2011 11:49:42 +0100
I'm Old Gregg wrote:



Try this

www.globalgadgetuk.com/Personal.htm


Greg

Wonderful!

"Note for UK customers: jamming equipment is illegal to use in the UK as it
violates section 8 of the 2006 Wireless Telegraphy Act, we are therefore
unable to supply jammers to any UK customer with the exception of certain
military and government departments who have the necessary authorisation from
the UK Office of Communications (Ofcom). Please note that no exceptions can be
made on this policy.

Due to non CE approval of these products we cannot sell these products
into any
European Union country.

Now what would Many Rice-Davies say about such a situation?

SH066PL2B £120.00 GBP"

And since when has the UK been outside the EU?

To be fair, they are saying that the reason because the jammers can't be
used in the UK is the UK WT Act. They probably haven't been able to
check the equivalent laws in the other EU countries, so they are saying
that lack of EU approval is a 'stop all'. Unfortunately, the essentially
fake EU testing on certain PLT products hasn't stopped PLT. Maybe these
jammers could be subjected to similarly-rigorous testing, and then
qualify for the much coveted CE mark?
--
Ian

Ian wrote:
In message , Bill Wright
writes

http://downloads.bbc.co.uk/rd/pubs/w...les/WHP195.pdf


Pictures and sound here,

http://www.youtube.com/watch?v=dK3MuTPlHS0

Hmm. a rather crappy radio tuned into a weak FM station (or maybe even AM?)
sat right next to a laptop.

I'm not denying that there's interference but it's hardly a scientific
demonstration.

Tim

Seconded, I don't use homeplugs but when I boot up my laptop it causes
interference to my DAB radio.

Ian wrote:


Pictures and sound here,

http://www.youtube.com/watch?v=dK3MuTPlHS0

That's a complete fraud! He can't be trusted: he has a ponytail.

Bill

Roderick Stewart wrote:

Deliberate trouble doesn't seem to
me to be a very good thing, and those who perpetrate it automatically weaken
all their own arguments about any trouble caused by anybody else.

So you would have let the Germans take over Europe then? Sometimes it is
morally justifiable to fight fire with fire.

We have to consider the greater good, and it seems to me that the
powers-that-be have not considered that, or have acted on incorrect
technical advice. In such a case, if they don't hastily correct their
mistake it is the right and duty of citizens to take unilateral action.

You see, I'm in favour of acting like a man, not a frightened sheep. If
UK citizens were more belligerent the powers-that-be would soon realise
that they can't walk all over us, imposing petty rules here there and
everywhere.

Bill

Tim Downie wrote:

Hmm. a rather crappy radio tuned into a weak FM station (or maybe even
AM?) sat right next to a laptop.

It was HF wasn't it?


I'm not denying that there's interference but it's hardly a scientific
demonstration.

He should have taken the radio for a walk.

Bill

In article , Bill Wright wrote:
Deliberate trouble doesn't seem to
me to be a very good thing, and those who perpetrate it automatically weaken
all their own arguments about any trouble caused by anybody else.

So you would have let the Germans take over Europe then? Sometimes it is
morally justifiable to fight fire with fire.

We seem to have made a bit of a conceptual leap from the use of homeplug
networking devices, whether they cause any real problems for anybody, and whether
it is acceptable for anyone to sabotage their use. I think the Nazis caused
slightly more bother than a bit of RFI.

For what it's worth, I've just made a quick crude check of the amount of RFI from
a few nearby electronic devices by waving a small shortwave radio in their
general vicinity. Between a Devolo 85Mb/s homeplug device, a Draytek ADSL router
and the Samsung computer monitor I'm sitting in front of right now, the homeplug
put out the *lowest* amount of audible rubbish, only audible at all with the
radio really close to it, suggesting that if anybody thinks these things should
be made illegal, logically we should outlaw monitors and routers first.

Rod.

In article , Paul Ratcliffe wrote:
The matter of "unapproved" modems was fairly contentious at the time, so if
there had ever been any real problems resulting from their use I think we
would have heard. If you know of any such case, please tell.

But that didn't affect any other piece of kit, nor indeed anybody else's
kit. PLTs are a completely different kettle of fish, as you know full
well.

I think the philosophy behind the approval scheme for modems was that they
potentially *could* affect other people's kit by putting unwelcome signals or
dangerous voltages back into the phone line. I have to agree that bad design
could do this, but I never heard or read of any case where it had done.

I've used wired ethernet. It works well, but to install it properly would
involve a lot of redecorating. Homeplugs are simple, convenient, they work,
and I haven't noticed anything else not working as a result.

Just because YOU haven't noticed it doesn't mean there isn't a problem.

I haven't noticed anybody knocking at my door to complain about anything
*they've* noticed either.

Rod.
--
Virtual Access V6.3 free usenet/email software from
http://sourceforge.net/projects/virtual-access/