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On 08/01/2014 11:36, Johny B Good wrote:

Modern 4 wire dropwires have the wires laid parallel with a common
twist (quad). This actually gives better crosstalk immunity than if
each pair had been given their own seperate twist and then laid up
alongside each other (with or without yet another twist).

In a quad, it's the diagonally opposite wires which are used to form
each of the two balanced pairs.

Like 'Star Quad' microphone cable ?

http://www.soundonsound.com/sos/nov0...s/qa1109_4.htm


--
Mark
Please replace invalid and invalid with gmx and net to reply.

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On Wed, 08 Jan 2014 11:49:32 +0000, Mark Carver
wrote:

On 08/01/2014 11:36, Johny B Good wrote:

Modern 4 wire dropwires have the wires laid parallel with a common
twist (quad). This actually gives better crosstalk immunity than if
each pair had been given their own seperate twist and then laid up
alongside each other (with or without yet another twist).

In a quad, it's the diagonally opposite wires which are used to form
each of the two balanced pairs.

Like 'Star Quad' microphone cable ?

http://www.soundonsound.com/sos/nov0...s/qa1109_4.htm

That's it exactly. The article even mentions its telecommunications
origins.
--
Regards, J B Good

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Johny B Good wrote:
On Wed, 08 Jan 2014 11:49:32 +0000, Mark Carver
wrote:

On 08/01/2014 11:36, Johny B Good wrote:

Modern 4 wire dropwires have the wires laid parallel with a common
twist (quad). This actually gives better crosstalk immunity than if
each pair had been given their own seperate twist and then laid up
alongside each other (with or without yet another twist).

In a quad, it's the diagonally opposite wires which are used to form
each of the two balanced pairs.
Like 'Star Quad' microphone cable ?

http://www.soundonsound.com/sos/nov0...s/qa1109_4.htm

That's it exactly. The article even mentions its telecommunications
origins.

This is all very interesting.

Bill

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Jim Lesurf wrote:

In practice that may mean it does cause reception problems for some
people - who have no idea of the reason and so don't raise a complaint
identifying that mains RF devices are a problem.

Fair point. But let's look at it the other way? How many properly
investigated and documented reports of this actually causing a problem
have you identified?

As far as I can tell, most people on this newsgroup say "Yes, it could
definitely cause a problem." A few go so far as to say "Yes, I heard
of a case where it was causing a problem).

Few, though, say "Well, go on then: let's have a look at some real data
and then we'll know for sure how big the problem is".

There is one other important point I want to make: problems can arise
even when the transmitting equipment is *legal*, depending on how close
you are to it. There is nothing magic, or black-and-white, about the
current legal parameters for transmission power, etc. They were set at
a suitably reasonable level, taking into account the requirements of
the particular service and the associated risks.

The potential for interference between different equipments is always
there. All you can hope to do is minimise it, whilst still maintaining
the utility RF-based services provide.

--
SteveT

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On Wed, 08 Jan 2014 11:49:32 +0000, Mark Carver
wrote:

On 08/01/2014 11:36, Johny B Good wrote:

Modern 4 wire dropwires have the wires laid parallel with a common
twist (quad). This actually gives better crosstalk immunity than if
each pair had been given their own seperate twist and then laid up
alongside each other (with or without yet another twist).

In a quad, it's the diagonally opposite wires which are used to form
each of the two balanced pairs.

Like 'Star Quad' microphone cable ?

http://www.soundonsound.com/sos/nov0...s/qa1109_4.htm

That's it exactly. The article even mentions its telecommunications
origins.
--
Regards, J B Good

Extending wi-fi
 

In message , Jim Lesurf
writes
In article , Roderick
Stewart
wrote:
On Wed, 08 Jan 2014 07:17:05 +0000, Mark Carver
wrote:


The telephone wires are explicitly balanced, by being made as twisted
pairs. That balances them against environmental asymmetries.

All the overhead 'drop wires' I've ever seen close up are 'shotgun'
rather than twisted ?

You mean parallel wires with constant spacing, like mains cable?

There are various mains cables around our house. They don't all have the
same wire spacing or diameters. Some are three wire, some are two. None, so
far as I know, behave in a balanced way at RF.

I'm no expert on domestic mains wiring but AIUI the wires to the light
fittings tend to only switch one 'arm' of the connection. If so, leaving a
'spur' of a single wire for the RF. Rather more like an antenna than
balanced impedance-matched cable. One per room. Antenna array.

But apparently OfCom have decided the result is not a "transmitter". Wonder
how many of the decision makers ever did Radio 101 at Uni...

There are lots of commercial interests who knew they had an expanding
market for PLT equipment, and in the end, I think it's a case of money
talks even more than radio amateurs do (and that's quite a lot).
--
Ian

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In message , Steve Thackery
writes
Jim Lesurf wrote:

In practice that may mean it does cause reception problems for some
people - who have no idea of the reason and so don't raise a complaint
identifying that mains RF devices are a problem.

Fair point. But let's look at it the other way? How many properly
investigated and documented reports of this actually causing a problem
have you identified?

As far as I can tell, most people on this newsgroup say "Yes, it could
definitely cause a problem." A few go so far as to say "Yes, I heard
of a case where it was causing a problem).

Few, though, say "Well, go on then: let's have a look at some real data
and then we'll know for sure how big the problem is".

There is one other important point I want to make: problems can arise
even when the transmitting equipment is *legal*, depending on how close
you are to it. There is nothing magic, or black-and-white, about the
current legal parameters for transmission power, etc. They were set at
a suitably reasonable level, taking into account the requirements of
the particular service and the associated risks.

The potential for interference between different equipments is always
there. All you can hope to do is minimise it, whilst still maintaining
the utility RF-based services provide.

I'm sure Steve is fully aware of the problems of PLT. If not, may I
refer him to the following websites:
http://www.ban-plt.co.uk/truth-lies.php
http://www.ukqrm.org.uk/plt.php
www.elmac.co.uk/pdfs/whyPLTisbadforemc.pdf?
http://www.compliance-club.com/default.aspx?id=17
http://www.emcuk.co.uk/awareness/Pag...s/IssuesWithBr
oadband.htm
and many more.
--
Ian

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Ian Jackson wrote:

I'm sure Steve is fully aware of the problems of PLT. If not, may I
refer him to the following websites:
http://www.ban-plt.co.uk/truth-lies.php
http://www.ukqrm.org.uk/plt.php
www.elmac.co.uk/pdfs/whyPLTisbadforemc.pdf?
http://www.compliance-club.com/default.aspx?id=17
http://www.emcuk.co.uk/awareness/Pag...ples/IssuesWit
hBr oadband.htm and many more.

Thanks, Ian. I will indeed take a look at those sites when I've
finished all my university assignments that I should have done over
Christmas!

--
SteveT

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In article , Steve Thackery
wrote:
Jim Lesurf wrote:

In practice that may mean it does cause reception problems for some
people - who have no idea of the reason and so don't raise a complaint
identifying that mains RF devices are a problem.

Fair point. But let's look at it the other way? How many properly
investigated and documented reports of this actually causing a problem
have you identified?

None. I've done no first-hand investigations of the matter. The closest
I've come to that it discuss it with people at the BBC and elsewhere who've
done work on the area to assess the impact. And to look at some of the
reports they've produced on it.

What have you done to test if many people are affected?
[Same question for others reading this.]

The potential for interference between different equipments is always
there. All you can hope to do is minimise it, whilst still maintaining
the utility RF-based services provide.

Problem is that you have no way to know how much you may have failed if
those adversely affected don't know the reason for the problems they get.

Jim

--
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

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Jim Lesurf wrote:

I'm no expert on domestic mains wiring but AIUI the wires to the light
fittings tend to only switch one 'arm' of the connection. If so, leaving a
'spur' of a single wire for the RF. Rather more like an antenna than
balanced impedance-matched cable. One per room. Antenna array.

But apparently OfCom have decided the result is not a "transmitter". Wonder
how many of the decision makers ever did Radio 101 at Uni...

I wonder how they'd react if someone connected an HF tx RF output to the
mains via an ATU and turned up the wick?

Bill